+ }
+
+ /* We need the maximum number of entries regardless of the format the
+ * application sets here.
+ */
+ {
+ png_uint_32 cmap_entries;
+
+ switch (png_ptr->color_type)
+ {
+ case PNG_COLOR_TYPE_GRAY:
+ cmap_entries = 1U << png_ptr->bit_depth;
+ break;
+
+ case PNG_COLOR_TYPE_PALETTE:
+ cmap_entries = png_ptr->num_palette;
+ break;
+
+ default:
+ cmap_entries = 256;
+ break;
+ }
+
+ if (cmap_entries > 256)
+ cmap_entries = 256;
+
+ image->colormap_entries = cmap_entries;
+ }
+
+ return 1;
+}
+
+#ifdef PNG_STDIO_SUPPORTED
+int PNGAPI
+png_image_begin_read_from_stdio(png_imagep image, FILE* file)
+{
+ if (image != NULL && image->version == PNG_IMAGE_VERSION)
+ {
+ if (file != NULL)
+ {
+ if (png_image_read_init(image))
+ {
+ /* This is slightly evil, but png_init_io doesn't do anything other
+ * than this and we haven't changed the standard IO functions so
+ * this saves a 'safe' function.
+ */
+ image->opaque->png_ptr->io_ptr = file;
+ return png_safe_execute(image, png_image_read_header, image);
+ }
+ }
+
+ else
+ return png_image_error(image,
+ "png_image_begin_read_from_stdio: invalid argument");
+ }
+
+ else if (image != NULL)
+ return png_image_error(image,
+ "png_image_begin_read_from_stdio: incorrect PNG_IMAGE_VERSION");
+
+ return 0;
+}
+
+int PNGAPI
+png_image_begin_read_from_file(png_imagep image, const char *file_name)
+{
+ if (image != NULL && image->version == PNG_IMAGE_VERSION)
+ {
+ if (file_name != NULL)
+ {
+ FILE *fp = fopen(file_name, "rb");
+
+ if (fp != NULL)
+ {
+ if (png_image_read_init(image))
+ {
+ image->opaque->png_ptr->io_ptr = fp;
+ image->opaque->owned_file = 1;
+ return png_safe_execute(image, png_image_read_header, image);
+ }
+
+ /* Clean up: just the opened file. */
+ (void)fclose(fp);
+ }
+
+ else
+ return png_image_error(image, strerror(errno));
+ }
+
+ else
+ return png_image_error(image,
+ "png_image_begin_read_from_file: invalid argument");
+ }
+
+ else if (image != NULL)
+ return png_image_error(image,
+ "png_image_begin_read_from_file: incorrect PNG_IMAGE_VERSION");
+
+ return 0;
+}
+#endif /* PNG_STDIO_SUPPORTED */
+
+static void PNGCBAPI
+png_image_memory_read(png_structp png_ptr, png_bytep out, png_size_t need)
+{
+ if (png_ptr != NULL)
+ {
+ png_imagep image = png_voidcast(png_imagep, png_ptr->io_ptr);
+ if (image != NULL)
+ {
+ png_controlp cp = image->opaque;
+ if (cp != NULL)
+ {
+ png_const_bytep memory = cp->memory;
+ png_size_t size = cp->size;
+
+ if (memory != NULL && size >= need)
+ {
+ memcpy(out, memory, need);
+ cp->memory = memory + need;
+ cp->size = size - need;
+ return;
+ }
+
+ png_error(png_ptr, "read beyond end of data");
+ }
+ }
+
+ png_error(png_ptr, "invalid memory read");
+ }
+}
+
+int PNGAPI png_image_begin_read_from_memory(png_imagep image,
+ png_const_voidp memory, png_size_t size)
+{
+ if (image != NULL && image->version == PNG_IMAGE_VERSION)
+ {
+ if (memory != NULL && size > 0)
+ {
+ if (png_image_read_init(image))
+ {
+ /* Now set the IO functions to read from the memory buffer and
+ * store it into io_ptr. Again do this in-place to avoid calling a
+ * libpng function that requires error handling.
+ */
+ image->opaque->memory = png_voidcast(png_const_bytep, memory);
+ image->opaque->size = size;
+ image->opaque->png_ptr->io_ptr = image;
+ image->opaque->png_ptr->read_data_fn = png_image_memory_read;
+
+ return png_safe_execute(image, png_image_read_header, image);
+ }
+ }
+
+ else
+ return png_image_error(image,
+ "png_image_begin_read_from_memory: invalid argument");
+ }
+
+ else if (image != NULL)
+ return png_image_error(image,
+ "png_image_begin_read_from_memory: incorrect PNG_IMAGE_VERSION");
+
+ return 0;
+}
+
+/* Utility function to skip chunks that are not used by the simplified image
+ * read functions and an appropriate macro to call it.
+ */
+#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
+static void
+png_image_skip_unused_chunks(png_structrp png_ptr)
+{
+ /* Prepare the reader to ignore all recognized chunks whose data will not
+ * be used, i.e., all chunks recognized by libpng except for those
+ * involved in basic image reading:
+ *
+ * IHDR, PLTE, IDAT, IEND
+ *
+ * Or image data handling:
+ *
+ * tRNS, bKGD, gAMA, cHRM, sRGB, iCCP and sBIT.
+ *
+ * This provides a small performance improvement and eliminates any
+ * potential vulnerability to security problems in the unused chunks.
+ */
+ {
+ static PNG_CONST png_byte chunks_to_process[] = {
+ 98, 75, 71, 68, '\0', /* bKGD */
+ 99, 72, 82, 77, '\0', /* cHRM */
+ 103, 65, 77, 65, '\0', /* gAMA */
+ 105, 67, 67, 80, '\0', /* iCCP */
+ 115, 66, 73, 84, '\0', /* sBIT */
+ 115, 82, 71, 66, '\0', /* sRGB */
+ };
+
+ /* Ignore unknown chunks and all other chunks except for the
+ * IHDR, PLTE, tRNS, IDAT, and IEND chunks.
+ */
+ png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_NEVER,
+ NULL, -1);
+
+ /* But do not ignore image data handling chunks */
+ png_set_keep_unknown_chunks(png_ptr, PNG_HANDLE_CHUNK_AS_DEFAULT,
+ chunks_to_process, (sizeof chunks_to_process)/5);
+ }
+}
+
+# define PNG_SKIP_CHUNKS(p) png_image_skip_unused_chunks(p)
+#else
+# define PNG_SKIP_CHUNKS(p) ((void)0)
+#endif /* PNG_HANDLE_AS_UNKNOWN_SUPPORTED */
+
+/* The following macro gives the exact rounded answer for all values in the
+ * range 0..255 (it actually divides by 51.2, but the rounding still generates
+ * the correct numbers 0..5
+ */
+#define PNG_DIV51(v8) (((v8) * 5 + 130) >> 8)
+
+/* Utility functions to make particular color-maps */
+static void
+set_file_encoding(png_image_read_control *display)
+{
+ png_fixed_point g = display->image->opaque->png_ptr->colorspace.gamma;
+ if (png_gamma_significant(g))
+ {
+ if (png_gamma_not_sRGB(g))
+ {
+ display->file_encoding = E_FILE;
+ display->gamma_to_linear = png_reciprocal(g);
+ }
+
+ else
+ display->file_encoding = E_sRGB;
+ }
+
+ else
+ display->file_encoding = E_LINEAR8;
+}
+
+static unsigned int
+decode_gamma(png_image_read_control *display, png_uint_32 value, int encoding)
+{
+ if (encoding == E_FILE) /* double check */
+ encoding = display->file_encoding;
+
+ if (encoding == E_NOTSET) /* must be the file encoding */
+ {
+ set_file_encoding(display);
+ encoding = display->file_encoding;
+ }
+
+ switch (encoding)
+ {
+ case E_FILE:
+ value = png_gamma_16bit_correct(value*257, display->gamma_to_linear);
+ break;
+
+ case E_sRGB:
+ value = png_sRGB_table[value];
+ break;
+
+ case E_LINEAR:
+ break;
+
+ case E_LINEAR8:
+ value *= 257;
+ break;
+
+ default:
+ png_error(display->image->opaque->png_ptr,
+ "unexpected encoding (internal error)");
+ break;
+ }
+
+ return value;
+}
+
+static png_uint_32
+png_colormap_compose(png_image_read_control *display,
+ png_uint_32 foreground, int foreground_encoding, png_uint_32 alpha,
+ png_uint_32 background, int encoding)
+{
+ /* The file value is composed on the background, the background has the given
+ * encoding and so does the result, the file is encoded with E_FILE and the
+ * file and alpha are 8-bit values. The (output) encoding will always be
+ * E_LINEAR or E_sRGB.
+ */
+ png_uint_32 f = decode_gamma(display, foreground, foreground_encoding);
+ png_uint_32 b = decode_gamma(display, background, encoding);
+
+ /* The alpha is always an 8-bit value (it comes from the palette), the value
+ * scaled by 255 is what PNG_sRGB_FROM_LINEAR requires.
+ */
+ f = f * alpha + b * (255-alpha);
+
+ if (encoding == E_LINEAR)
+ {
+ /* Scale to 65535; divide by 255, approximately (in fact this is extremely
+ * accurate, it divides by 255.00000005937181414556, with no overflow.)
+ */
+ f *= 257; /* Now scaled by 65535 */
+ f += f >> 16;
+ f = (f+32768) >> 16;
+ }
+
+ else /* E_sRGB */
+ f = PNG_sRGB_FROM_LINEAR(f);
+
+ return f;
+}
+
+/* NOTE: E_LINEAR values to this routine must be 16-bit, but E_FILE values must
+ * be 8-bit.
+ */
+static void
+png_create_colormap_entry(png_image_read_control *display,
+ png_uint_32 ip, png_uint_32 red, png_uint_32 green, png_uint_32 blue,
+ png_uint_32 alpha, int encoding)
+{
+ png_imagep image = display->image;
+ const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) ?
+ E_LINEAR : E_sRGB;
+ const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
+ (red != green || green != blue);
+
+ if (ip > 255)
+ png_error(image->opaque->png_ptr, "color-map index out of range");
+
+ /* Update the cache with whether the file gamma is significantly different
+ * from sRGB.
+ */
+ if (encoding == E_FILE)
+ {
+ if (display->file_encoding == E_NOTSET)
+ set_file_encoding(display);
+
+ /* Note that the cached value may be E_FILE too, but if it is then the
+ * gamma_to_linear member has been set.
+ */
+ encoding = display->file_encoding;
+ }
+
+ if (encoding == E_FILE)
+ {
+ png_fixed_point g = display->gamma_to_linear;
+
+ red = png_gamma_16bit_correct(red*257, g);
+ green = png_gamma_16bit_correct(green*257, g);
+ blue = png_gamma_16bit_correct(blue*257, g);
+
+ if (convert_to_Y || output_encoding == E_LINEAR)
+ {
+ alpha *= 257;
+ encoding = E_LINEAR;
+ }
+
+ else
+ {
+ red = PNG_sRGB_FROM_LINEAR(red * 255);
+ green = PNG_sRGB_FROM_LINEAR(green * 255);
+ blue = PNG_sRGB_FROM_LINEAR(blue * 255);
+ encoding = E_sRGB;
+ }
+ }
+
+ else if (encoding == E_LINEAR8)
+ {
+ /* This encoding occurs quite frequently in test cases because PngSuite
+ * includes a gAMA 1.0 chunk with most images.
+ */
+ red *= 257;
+ green *= 257;
+ blue *= 257;
+ alpha *= 257;
+ encoding = E_LINEAR;
+ }
+
+ else if (encoding == E_sRGB && (convert_to_Y || output_encoding == E_LINEAR))
+ {
+ /* The values are 8-bit sRGB values, but must be converted to 16-bit
+ * linear.
+ */
+ red = png_sRGB_table[red];
+ green = png_sRGB_table[green];
+ blue = png_sRGB_table[blue];
+ alpha *= 257;
+ encoding = E_LINEAR;
+ }
+
+ /* This is set if the color isn't gray but the output is. */
+ if (encoding == E_LINEAR)
+ {
+ if (convert_to_Y)
+ {
+ /* NOTE: these values are copied from png_do_rgb_to_gray */
+ png_uint_32 y = (png_uint_32)6968 * red + (png_uint_32)23434 * green +
+ (png_uint_32)2366 * blue;
+
+ if (output_encoding == E_LINEAR)
+ y = (y + 16384) >> 15;
+
+ else
+ {
+ /* y is scaled by 32768, we need it scaled by 255: */
+ y = (y + 128) >> 8;
+ y *= 255;
+ y = PNG_sRGB_FROM_LINEAR((y + 64) >> 7);
+ encoding = E_sRGB;
+ }
+
+ blue = red = green = y;
+ }
+
+ else if (output_encoding == E_sRGB)
+ {
+ red = PNG_sRGB_FROM_LINEAR(red * 255);
+ green = PNG_sRGB_FROM_LINEAR(green * 255);
+ blue = PNG_sRGB_FROM_LINEAR(blue * 255);
+ alpha = PNG_DIV257(alpha);
+ encoding = E_sRGB;
+ }
+ }
+
+ if (encoding != output_encoding)
+ png_error(image->opaque->png_ptr, "bad encoding (internal error)");
+
+ /* Store the value. */
+ {
+# ifdef PNG_FORMAT_BGR_SUPPORTED
+ const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
+ (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
+# else
+# define afirst 0
+# endif
+# ifdef PNG_FORMAT_BGR_SUPPORTED
+ const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) ? 2 : 0;
+# else
+# define bgr 0
+# endif
+
+ if (output_encoding == E_LINEAR)
+ {
+ png_uint_16p entry = png_voidcast(png_uint_16p, display->colormap);
+
+ entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
+
+ /* The linear 16-bit values must be pre-multiplied by the alpha channel
+ * value, if less than 65535 (this is, effectively, composite on black
+ * if the alpha channel is removed.)
+ */
+ switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
+ {
+ case 4:
+ entry[afirst ? 0 : 3] = (png_uint_16)alpha;
+ /* FALL THROUGH */
+
+ case 3:
+ if (alpha < 65535)
+ {
+ if (alpha > 0)
+ {
+ blue = (blue * alpha + 32767U)/65535U;
+ green = (green * alpha + 32767U)/65535U;
+ red = (red * alpha + 32767U)/65535U;
+ }
+
+ else
+ red = green = blue = 0;
+ }
+ entry[afirst + (2 ^ bgr)] = (png_uint_16)blue;
+ entry[afirst + 1] = (png_uint_16)green;
+ entry[afirst + bgr] = (png_uint_16)red;
+ break;
+
+ case 2:
+ entry[1 ^ afirst] = (png_uint_16)alpha;
+ /* FALL THROUGH */
+
+ case 1:
+ if (alpha < 65535)
+ {
+ if (alpha > 0)
+ green = (green * alpha + 32767U)/65535U;
+
+ else
+ green = 0;
+ }
+ entry[afirst] = (png_uint_16)green;
+ break;
+
+ default:
+ break;
+ }
+ }
+
+ else /* output encoding is E_sRGB */
+ {
+ png_bytep entry = png_voidcast(png_bytep, display->colormap);
+
+ entry += ip * PNG_IMAGE_SAMPLE_CHANNELS(image->format);
+
+ switch (PNG_IMAGE_SAMPLE_CHANNELS(image->format))
+ {
+ case 4:
+ entry[afirst ? 0 : 3] = (png_byte)alpha;
+ case 3:
+ entry[afirst + (2 ^ bgr)] = (png_byte)blue;
+ entry[afirst + 1] = (png_byte)green;
+ entry[afirst + bgr] = (png_byte)red;
+ break;
+
+ case 2:
+ entry[1 ^ afirst] = (png_byte)alpha;
+ case 1:
+ entry[afirst] = (png_byte)green;
+ break;
+
+ default:
+ break;
+ }
+ }
+
+# ifdef afirst
+# undef afirst
+# endif
+# ifdef bgr
+# undef bgr
+# endif
+ }
+}
+
+static int
+make_gray_file_colormap(png_image_read_control *display)
+{
+ unsigned int i;
+
+ for (i=0; i<256; ++i)
+ png_create_colormap_entry(display, i, i, i, i, 255, E_FILE);
+
+ return i;
+}
+
+static int
+make_gray_colormap(png_image_read_control *display)
+{
+ unsigned int i;
+
+ for (i=0; i<256; ++i)
+ png_create_colormap_entry(display, i, i, i, i, 255, E_sRGB);
+
+ return i;
+}
+#define PNG_GRAY_COLORMAP_ENTRIES 256
+
+static int
+make_ga_colormap(png_image_read_control *display)
+{
+ unsigned int i, a;
+
+ /* Alpha is retained, the output will be a color-map with entries
+ * selected by six levels of alpha. One transparent entry, 6 gray
+ * levels for all the intermediate alpha values, leaving 230 entries
+ * for the opaque grays. The color-map entries are the six values
+ * [0..5]*51, the GA processing uses PNG_DIV51(value) to find the
+ * relevant entry.
+ *
+ * if (alpha > 229) // opaque
+ * {
+ * // The 231 entries are selected to make the math below work:
+ * base = 0;
+ * entry = (231 * gray + 128) >> 8;
+ * }
+ * else if (alpha < 26) // transparent
+ * {
+ * base = 231;
+ * entry = 0;
+ * }
+ * else // partially opaque
+ * {
+ * base = 226 + 6 * PNG_DIV51(alpha);
+ * entry = PNG_DIV51(gray);
+ * }
+ */
+ i = 0;
+ while (i < 231)
+ {
+ unsigned int gray = (i * 256 + 115) / 231;
+ png_create_colormap_entry(display, i++, gray, gray, gray, 255, E_sRGB);
+ }
+
+ /* 255 is used here for the component values for consistency with the code
+ * that undoes premultiplication in pngwrite.c.
+ */
+ png_create_colormap_entry(display, i++, 255, 255, 255, 0, E_sRGB);
+
+ for (a=1; a<5; ++a)
+ {
+ unsigned int g;
+
+ for (g=0; g<6; ++g)
+ png_create_colormap_entry(display, i++, g*51, g*51, g*51, a*51,
+ E_sRGB);
+ }
+
+ return i;
+}
+
+#define PNG_GA_COLORMAP_ENTRIES 256
+
+static int
+make_rgb_colormap(png_image_read_control *display)
+{
+ unsigned int i, r;
+
+ /* Build a 6x6x6 opaque RGB cube */
+ for (i=r=0; r<6; ++r)
+ {
+ unsigned int g;
+
+ for (g=0; g<6; ++g)
+ {
+ unsigned int b;
+
+ for (b=0; b<6; ++b)
+ png_create_colormap_entry(display, i++, r*51, g*51, b*51, 255,
+ E_sRGB);
+ }
+ }
+
+ return i;
+}
+
+#define PNG_RGB_COLORMAP_ENTRIES 216
+
+/* Return a palette index to the above palette given three 8-bit sRGB values. */
+#define PNG_RGB_INDEX(r,g,b) \
+ ((png_byte)(6 * (6 * PNG_DIV51(r) + PNG_DIV51(g)) + PNG_DIV51(b)))
+
+static int
+png_image_read_colormap(png_voidp argument)
+{
+ png_image_read_control *display =
+ png_voidcast(png_image_read_control*, argument);
+ const png_imagep image = display->image;
+
+ const png_structrp png_ptr = image->opaque->png_ptr;
+ const png_uint_32 output_format = image->format;
+ const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) ?
+ E_LINEAR : E_sRGB;
+
+ unsigned int cmap_entries;
+ unsigned int output_processing; /* Output processing option */
+ unsigned int data_encoding = E_NOTSET; /* Encoding libpng must produce */
+
+ /* Background information; the background color and the index of this color
+ * in the color-map if it exists (else 256).
+ */
+ unsigned int background_index = 256;
+ png_uint_32 back_r, back_g, back_b;
+
+ /* Flags to accumulate things that need to be done to the input. */
+ int expand_tRNS = 0;
+
+ /* Exclude the NYI feature of compositing onto a color-mapped buffer; it is
+ * very difficult to do, the results look awful, and it is difficult to see
+ * what possible use it is because the application can't control the
+ * color-map.
+ */
+ if (((png_ptr->color_type & PNG_COLOR_MASK_ALPHA) != 0 ||
+ png_ptr->num_trans > 0) /* alpha in input */ &&
+ ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0) /* no alpha in output */)
+ {
+ if (output_encoding == E_LINEAR) /* compose on black */
+ back_b = back_g = back_r = 0;
+
+ else if (display->background == NULL /* no way to remove it */)
+ png_error(png_ptr,
+ "a background color must be supplied to remove alpha/transparency");
+
+ /* Get a copy of the background color (this avoids repeating the checks
+ * below.) The encoding is 8-bit sRGB or 16-bit linear, depending on the
+ * output format.
+ */
+ else
+ {
+ back_g = display->background->green;
+ if (output_format & PNG_FORMAT_FLAG_COLOR)
+ {
+ back_r = display->background->red;
+ back_b = display->background->blue;
+ }
+ else
+ back_b = back_r = back_g;
+ }
+ }
+
+ else if (output_encoding == E_LINEAR)
+ back_b = back_r = back_g = 65535;
+
+ else
+ back_b = back_r = back_g = 255;
+
+ /* Default the input file gamma if required - this is necessary because
+ * libpng assumes that if no gamma information is present the data is in the
+ * output format, but the simplified API deduces the gamma from the input
+ * format.
+ */
+ if ((png_ptr->colorspace.flags & PNG_COLORSPACE_HAVE_GAMMA) == 0)
+ {
+ /* Do this directly, not using the png_colorspace functions, to ensure
+ * that it happens even if the colorspace is invalid (though probably if
+ * it is the setting will be ignored) Note that the same thing can be
+ * achieved at the application interface with png_set_gAMA.
+ */
+ if (png_ptr->bit_depth == 16 &&
+ (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
+ png_ptr->colorspace.gamma = PNG_GAMMA_LINEAR;
+
+ else
+ png_ptr->colorspace.gamma = PNG_GAMMA_sRGB_INVERSE;
+
+ png_ptr->colorspace.flags |= PNG_COLORSPACE_HAVE_GAMMA;
+ }
+
+ /* Decide what to do based on the PNG color type of the input data. The
+ * utility function png_create_colormap_entry deals with most aspects of the
+ * output transformations; this code works out how to produce bytes of
+ * color-map entries from the original format.
+ */
+ switch (png_ptr->color_type)
+ {
+ case PNG_COLOR_TYPE_GRAY:
+ if (png_ptr->bit_depth <= 8)
+ {
+ /* There at most 256 colors in the output, regardless of
+ * transparency.
+ */
+ unsigned int step, i, val, trans = 256/*ignore*/, back_alpha = 0;
+
+ cmap_entries = 1U << png_ptr->bit_depth;
+ if (cmap_entries > image->colormap_entries)
+ png_error(png_ptr, "gray[8] color-map: too few entries");
+
+ step = 255 / (cmap_entries - 1);
+ output_processing = PNG_CMAP_NONE;
+
+ /* If there is a tRNS chunk then this either selects a transparent
+ * value or, if the output has no alpha, the background color.
+ */
+ if (png_ptr->num_trans > 0)
+ {
+ trans = png_ptr->trans_color.gray;
+
+ if ((output_format & PNG_FORMAT_FLAG_ALPHA) == 0)
+ back_alpha = output_encoding == E_LINEAR ? 65535 : 255;
+ }
+
+ /* png_create_colormap_entry just takes an RGBA and writes the
+ * corresponding color-map entry using the format from 'image',
+ * including the required conversion to sRGB or linear as
+ * appropriate. The input values are always either sRGB (if the
+ * gamma correction flag is 0) or 0..255 scaled file encoded values
+ * (if the function must gamma correct them).
+ */
+ for (i=val=0; i<cmap_entries; ++i, val += step)
+ {
+ /* 'i' is a file value. While this will result in duplicated
+ * entries for 8-bit non-sRGB encoded files it is necessary to
+ * have non-gamma corrected values to do tRNS handling.
+ */
+ if (i != trans)
+ png_create_colormap_entry(display, i, val, val, val, 255,
+ E_FILE/*8-bit with file gamma*/);
+
+ /* Else this entry is transparent. The colors don't matter if
+ * there is an alpha channel (back_alpha == 0), but it does no
+ * harm to pass them in; the values are not set above so this
+ * passes in white.
+ *
+ * NOTE: this preserves the full precision of the application
+ * supplied background color when it is used.
+ */
+ else
+ png_create_colormap_entry(display, i, back_r, back_g, back_b,
+ back_alpha, output_encoding);
+ }
+
+ /* We need libpng to preserve the original encoding. */
+ data_encoding = E_FILE;
+
+ /* The rows from libpng, while technically gray values, are now also
+ * color-map indicies; however, they may need to be expanded to 1
+ * byte per pixel. This is what png_set_packing does (i.e., it
+ * unpacks the bit values into bytes.)
+ */
+ if (png_ptr->bit_depth < 8)
+ png_set_packing(png_ptr);
+ }
+
+ else /* bit depth is 16 */
+ {
+ /* The 16-bit input values can be converted directly to 8-bit gamma
+ * encoded values; however, if a tRNS chunk is present 257 color-map
+ * entries are required. This means that the extra entry requires
+ * special processing; add an alpha channel, sacrifice gray level
+ * 254 and convert transparent (alpha==0) entries to that.
+ *
+ * Use libpng to chop the data to 8 bits. Convert it to sRGB at the
+ * same time to minimize quality loss. If a tRNS chunk is present
+ * this means libpng must handle it too; otherwise it is impossible
+ * to do the exact match on the 16-bit value.
+ *
+ * If the output has no alpha channel *and* the background color is
+ * gray then it is possible to let libpng handle the substitution by
+ * ensuring that the corresponding gray level matches the background
+ * color exactly.
+ */
+ data_encoding = E_sRGB;
+
+ if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
+ png_error(png_ptr, "gray[16] color-map: too few entries");
+
+ cmap_entries = make_gray_colormap(display);
+
+ if (png_ptr->num_trans > 0)
+ {
+ unsigned int back_alpha;
+
+ if (output_format & PNG_FORMAT_FLAG_ALPHA)
+ back_alpha = 0;
+
+ else
+ {
+ if (back_r == back_g && back_g == back_b)
+ {
+ /* Background is gray; no special processing will be
+ * required.
+ */
+ png_color_16 c;
+ png_uint_32 gray = back_g;
+
+ if (output_encoding == E_LINEAR)
+ {
+ gray = PNG_sRGB_FROM_LINEAR(gray * 255);
+
+ /* And make sure the corresponding palette entry
+ * matches.
+ */
+ png_create_colormap_entry(display, gray, back_g, back_g,
+ back_g, 65535, E_LINEAR);
+ }
+
+ /* The background passed to libpng, however, must be the
+ * sRGB value.
+ */
+ c.index = 0; /*unused*/
+ c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
+
+ /* NOTE: does this work without expanding tRNS to alpha?
+ * It should be the color->gray case below apparently
+ * doesn't.
+ */
+ png_set_background_fixed(png_ptr, &c,
+ PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+ 0/*gamma: not used*/);
+
+ output_processing = PNG_CMAP_NONE;
+ break;
+ }
+
+ back_alpha = output_encoding == E_LINEAR ? 65535 : 255;
+ }
+
+ /* output_processing means that the libpng-processed row will be
+ * 8-bit GA and it has to be processing to single byte color-map
+ * values. Entry 254 is replaced by either a completely
+ * transparent entry or by the background color at full
+ * precision (and the background color is not a simple gray leve
+ * in this case.)
+ */
+ expand_tRNS = 1;
+ output_processing = PNG_CMAP_TRANS;
+ background_index = 254;
+
+ /* And set (overwrite) color-map entry 254 to the actual
+ * background color at full precision.
+ */
+ png_create_colormap_entry(display, 254, back_r, back_g, back_b,
+ back_alpha, output_encoding);
+ }
+
+ else
+ output_processing = PNG_CMAP_NONE;
+ }
+ break;
+
+ case PNG_COLOR_TYPE_GRAY_ALPHA:
+ /* 8-bit or 16-bit PNG with two channels - gray and alpha. A minimum
+ * of 65536 combinations. If, however, the alpha channel is to be
+ * removed there are only 256 possibilities if the background is gray.
+ * (Otherwise there is a subset of the 65536 possibilities defined by
+ * the triangle between black, white and the background color.)
+ *
+ * Reduce 16-bit files to 8-bit and sRGB encode the result. No need to
+ * worry about tRNS matching - tRNS is ignored if there is an alpha
+ * channel.
+ */
+ data_encoding = E_sRGB;
+
+ if (output_format & PNG_FORMAT_FLAG_ALPHA)
+ {
+ if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
+ png_error(png_ptr, "gray+alpha color-map: too few entries");
+
+ cmap_entries = make_ga_colormap(display);
+
+ background_index = PNG_CMAP_GA_BACKGROUND;
+ output_processing = PNG_CMAP_GA;
+ }
+
+ else /* alpha is removed */
+ {
+ /* Alpha must be removed as the PNG data is processed when the
+ * background is a color because the G and A channels are
+ * independent and the vector addition (non-parallel vectors) is a
+ * 2-D problem.
+ *
+ * This can be reduced to the same algorithm as above by making a
+ * colormap containing gray levels (for the opaque grays), a
+ * background entry (for a transparent pixel) and a set of four six
+ * level color values, one set for each intermediate alpha value.
+ * See the comments in make_ga_colormap for how this works in the
+ * per-pixel processing.
+ *
+ * If the background is gray, however, we only need a 256 entry gray
+ * level color map. It is sufficient to make the entry generated
+ * for the background color be exactly the color specified.
+ */
+ if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0 ||
+ (back_r == back_g && back_g == back_b))
+ {
+ /* Background is gray; no special processing will be required. */
+ png_color_16 c;
+ png_uint_32 gray = back_g;
+
+ if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
+ png_error(png_ptr, "gray-alpha color-map: too few entries");
+
+ cmap_entries = make_gray_colormap(display);
+
+ if (output_encoding == E_LINEAR)
+ {
+ gray = PNG_sRGB_FROM_LINEAR(gray * 255);
+
+ /* And make sure the corresponding palette entry matches. */
+ png_create_colormap_entry(display, gray, back_g, back_g,
+ back_g, 65535, E_LINEAR);
+ }
+
+ /* The background passed to libpng, however, must be the sRGB
+ * value.
+ */
+ c.index = 0; /*unused*/
+ c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
+
+ png_set_background_fixed(png_ptr, &c,
+ PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+ 0/*gamma: not used*/);
+
+ output_processing = PNG_CMAP_NONE;
+ }
+
+ else
+ {
+ png_uint_32 i, a;
+
+ /* This is the same as png_make_ga_colormap, above, except that
+ * the entries are all opaque.
+ */
+ if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
+ png_error(png_ptr, "ga-alpha color-map: too few entries");
+
+ i = 0;
+ while (i < 231)
+ {
+ png_uint_32 gray = (i * 256 + 115) / 231;
+ png_create_colormap_entry(display, i++, gray, gray, gray,
+ 255, E_sRGB);
+ }
+
+ /* NOTE: this preserves the full precision of the application
+ * background color.
+ */
+ background_index = i;
+ png_create_colormap_entry(display, i++, back_r, back_g, back_b,
+ output_encoding == E_LINEAR ? 65535U : 255U, output_encoding);
+
+ /* For non-opaque input composite on the sRGB background - this
+ * requires inverting the encoding for each component. The input
+ * is still converted to the sRGB encoding because this is a
+ * reasonable approximate to the logarithmic curve of human
+ * visual sensitivity, at least over the narrow range which PNG
+ * represents. Consequently 'G' is always sRGB encoded, while
+ * 'A' is linear. We need the linear background colors.
+ */
+ if (output_encoding == E_sRGB) /* else already linear */
+ {
+ /* This may produce a value not exactly matching the
+ * background, but that's ok because these numbers are only
+ * used when alpha != 0
+ */
+ back_r = png_sRGB_table[back_r];
+ back_g = png_sRGB_table[back_g];
+ back_b = png_sRGB_table[back_b];
+ }
+
+ for (a=1; a<5; ++a)
+ {
+ unsigned int g;
+
+ /* PNG_sRGB_FROM_LINEAR expects a 16-bit linear value scaled
+ * by an 8-bit alpha value (0..255).
+ */
+ png_uint_32 alpha = 51 * a;
+ png_uint_32 back_rx = (255-alpha) * back_r;
+ png_uint_32 back_gx = (255-alpha) * back_g;
+ png_uint_32 back_bx = (255-alpha) * back_b;
+
+ for (g=0; g<6; ++g)
+ {
+ png_uint_32 gray = png_sRGB_table[g*51] * alpha;
+
+ png_create_colormap_entry(display, i++,
+ PNG_sRGB_FROM_LINEAR(gray + back_rx),
+ PNG_sRGB_FROM_LINEAR(gray + back_gx),
+ PNG_sRGB_FROM_LINEAR(gray + back_bx), 255, E_sRGB);
+ }
+ }
+
+ cmap_entries = i;
+ output_processing = PNG_CMAP_GA;
+ }
+ }
+ break;
+
+ case PNG_COLOR_TYPE_RGB:
+ case PNG_COLOR_TYPE_RGB_ALPHA:
+ /* Exclude the case where the output is gray; we can always handle this
+ * with the cases above.
+ */
+ if ((output_format & PNG_FORMAT_FLAG_COLOR) == 0)
+ {
+ /* The color-map will be grayscale, so we may as well convert the
+ * input RGB values to a simple grayscale and use the grayscale
+ * code above.
+ *
+ * NOTE: calling this apparently damages the recognition of the
+ * transparent color in background color handling; call
+ * png_set_tRNS_to_alpha before png_set_background_fixed.
+ */
+ png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE, -1,
+ -1);
+ data_encoding = E_sRGB;
+
+ /* The output will now be one or two 8-bit gray or gray+alpha
+ * channels. The more complex case arises when the input has alpha.
+ */
+ if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+ png_ptr->num_trans > 0) &&
+ (output_format & PNG_FORMAT_FLAG_ALPHA) != 0)
+ {
+ /* Both input and output have an alpha channel, so no background
+ * processing is required; just map the GA bytes to the right
+ * color-map entry.
+ */
+ expand_tRNS = 1;
+
+ if (PNG_GA_COLORMAP_ENTRIES > image->colormap_entries)
+ png_error(png_ptr, "rgb[ga] color-map: too few entries");
+
+ cmap_entries = make_ga_colormap(display);
+ background_index = PNG_CMAP_GA_BACKGROUND;
+ output_processing = PNG_CMAP_GA;
+ }
+
+ else
+ {
+ /* Either the input or the output has no alpha channel, so there
+ * will be no non-opaque pixels in the color-map; it will just be
+ * grayscale.
+ */
+ if (PNG_GRAY_COLORMAP_ENTRIES > image->colormap_entries)
+ png_error(png_ptr, "rgb[gray] color-map: too few entries");
+
+ /* Ideally this code would use libpng to do the gamma correction,
+ * but if an input alpha channel is to be removed we will hit the
+ * libpng bug in gamma+compose+rgb-to-gray (the double gamma
+ * correction bug). Fix this by dropping the gamma correction in
+ * this case and doing it in the palette; this will result in
+ * duplicate palette entries, but that's better than the
+ * alternative of double gamma correction.
+ */
+ if ((png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+ png_ptr->num_trans > 0) &&
+ png_gamma_not_sRGB(png_ptr->colorspace.gamma))
+ {
+ cmap_entries = make_gray_file_colormap(display);
+ data_encoding = E_FILE;
+ }
+
+ else
+ cmap_entries = make_gray_colormap(display);
+
+ /* But if the input has alpha or transparency it must be removed
+ */
+ if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+ png_ptr->num_trans > 0)
+ {
+ png_color_16 c;
+ png_uint_32 gray = back_g;
+
+ /* We need to ensure that the application background exists in
+ * the colormap and that completely transparent pixels map to
+ * it. Achieve this simply by ensuring that the entry
+ * selected for the background really is the background color.
+ */
+ if (data_encoding == E_FILE) /* from the fixup above */
+ {
+ /* The app supplied a gray which is in output_encoding, we
+ * need to convert it to a value of the input (E_FILE)
+ * encoding then set this palette entry to the required
+ * output encoding.
+ */
+ if (output_encoding == E_sRGB)
+ gray = png_sRGB_table[gray]; /* now E_LINEAR */
+
+ gray = PNG_DIV257(png_gamma_16bit_correct(gray,
+ png_ptr->colorspace.gamma)); /* now E_FILE */
+
+ /* And make sure the corresponding palette entry contains
+ * exactly the required sRGB value.
+ */
+ png_create_colormap_entry(display, gray, back_g, back_g,
+ back_g, 0/*unused*/, output_encoding);
+ }
+
+ else if (output_encoding == E_LINEAR)
+ {
+ gray = PNG_sRGB_FROM_LINEAR(gray * 255);
+
+ /* And make sure the corresponding palette entry matches.
+ */
+ png_create_colormap_entry(display, gray, back_g, back_g,
+ back_g, 0/*unused*/, E_LINEAR);
+ }
+
+ /* The background passed to libpng, however, must be the
+ * output (normally sRGB) value.
+ */
+ c.index = 0; /*unused*/
+ c.gray = c.red = c.green = c.blue = (png_uint_16)gray;
+
+ /* NOTE: the following is apparently a bug in libpng. Without
+ * it the transparent color recognition in
+ * png_set_background_fixed seems to go wrong.
+ */
+ expand_tRNS = 1;
+ png_set_background_fixed(png_ptr, &c,
+ PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+ 0/*gamma: not used*/);
+ }
+
+ output_processing = PNG_CMAP_NONE;
+ }
+ }
+
+ else /* output is color */
+ {
+ /* We could use png_quantize here so long as there is no transparent
+ * color or alpha; png_quantize ignores alpha. Easier overall just
+ * to do it once and using PNG_DIV51 on the 6x6x6 reduced RGB cube.
+ * Consequently we always want libpng to produce sRGB data.
+ */
+ data_encoding = E_sRGB;
+
+ /* Is there any transparency or alpha? */
+ if (png_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA ||
+ png_ptr->num_trans > 0)
+ {
+ /* Is there alpha in the output too? If so all four channels are
+ * processed into a special RGB cube with alpha support.
+ */
+ if (output_format & PNG_FORMAT_FLAG_ALPHA)
+ {
+ png_uint_32 r;
+
+ if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
+ png_error(png_ptr, "rgb+alpha color-map: too few entries");
+
+ cmap_entries = make_rgb_colormap(display);
+
+ /* Add a transparent entry. */
+ png_create_colormap_entry(display, cmap_entries, 255, 255,
+ 255, 0, E_sRGB);
+
+ /* This is stored as the background index for the processing
+ * algorithm.
+ */
+ background_index = cmap_entries++;
+
+ /* Add 27 r,g,b entries each with alpha 0.5. */
+ for (r=0; r<256; r = (r << 1) | 0x7f)
+ {
+ png_uint_32 g;
+
+ for (g=0; g<256; g = (g << 1) | 0x7f)
+ {
+ png_uint_32 b;
+
+ /* This generates components with the values 0, 127 and
+ * 255
+ */
+ for (b=0; b<256; b = (b << 1) | 0x7f)
+ png_create_colormap_entry(display, cmap_entries++,
+ r, g, b, 128, E_sRGB);
+ }
+ }
+
+ expand_tRNS = 1;
+ output_processing = PNG_CMAP_RGB_ALPHA;
+ }
+
+ else
+ {
+ /* Alpha/transparency must be removed. The background must
+ * exist in the color map (achieved by setting adding it after
+ * the 666 color-map). If the standard processing code will
+ * pick up this entry automatically that's all that is
+ * required; libpng can be called to do the background
+ * processing.
+ */
+ unsigned int sample_size =
+ PNG_IMAGE_SAMPLE_SIZE(output_format);
+ png_uint_32 r, g, b; /* sRGB background */
+
+ if (PNG_RGB_COLORMAP_ENTRIES+1+27 > image->colormap_entries)
+ png_error(png_ptr, "rgb-alpha color-map: too few entries");
+
+ cmap_entries = make_rgb_colormap(display);
+
+ png_create_colormap_entry(display, cmap_entries, back_r,
+ back_g, back_b, 0/*unused*/, output_encoding);
+
+ if (output_encoding == E_LINEAR)
+ {
+ r = PNG_sRGB_FROM_LINEAR(back_r * 255);
+ g = PNG_sRGB_FROM_LINEAR(back_g * 255);
+ b = PNG_sRGB_FROM_LINEAR(back_b * 255);
+ }
+
+ else
+ {
+ r = back_r;
+ g = back_g;
+ b = back_g;
+ }
+
+ /* Compare the newly-created color-map entry with the one the
+ * PNG_CMAP_RGB algorithm will use. If the two entries don't
+ * match, add the new one and set this as the background
+ * index.
+ */
+ if (memcmp((png_const_bytep)display->colormap +
+ sample_size * cmap_entries,
+ (png_const_bytep)display->colormap +
+ sample_size * PNG_RGB_INDEX(r,g,b),
+ sample_size) != 0)
+ {
+ /* The background color must be added. */
+ background_index = cmap_entries++;
+
+ /* Add 27 r,g,b entries each with created by composing with
+ * the background at alpha 0.5.
+ */
+ for (r=0; r<256; r = (r << 1) | 0x7f)
+ {
+ for (g=0; g<256; g = (g << 1) | 0x7f)
+ {
+ /* This generates components with the values 0, 127
+ * and 255
+ */
+ for (b=0; b<256; b = (b << 1) | 0x7f)
+ png_create_colormap_entry(display, cmap_entries++,
+ png_colormap_compose(display, r, E_sRGB, 128,
+ back_r, output_encoding),
+ png_colormap_compose(display, g, E_sRGB, 128,
+ back_g, output_encoding),
+ png_colormap_compose(display, b, E_sRGB, 128,
+ back_b, output_encoding),
+ 0/*unused*/, output_encoding);
+ }
+ }
+
+ expand_tRNS = 1;
+ output_processing = PNG_CMAP_RGB_ALPHA;
+ }
+
+ else /* background color is in the standard color-map */
+ {
+ png_color_16 c;
+
+ c.index = 0; /*unused*/
+ c.red = (png_uint_16)back_r;
+ c.gray = c.green = (png_uint_16)back_g;
+ c.blue = (png_uint_16)back_b;
+
+ png_set_background_fixed(png_ptr, &c,
+ PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+ 0/*gamma: not used*/);
+
+ output_processing = PNG_CMAP_RGB;
+ }
+ }
+ }
+
+ else /* no alpha or transparency in the input */
+ {
+ /* Alpha in the output is irrelevant, simply map the opaque input
+ * pixels to the 6x6x6 color-map.
+ */
+ if (PNG_RGB_COLORMAP_ENTRIES > image->colormap_entries)
+ png_error(png_ptr, "rgb color-map: too few entries");
+
+ cmap_entries = make_rgb_colormap(display);
+ output_processing = PNG_CMAP_RGB;
+ }
+ }
+ break;
+
+ case PNG_COLOR_TYPE_PALETTE:
+ /* It's already got a color-map. It may be necessary to eliminate the
+ * tRNS entries though.
+ */
+ {
+ unsigned int num_trans = png_ptr->num_trans;
+ png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
+ png_const_colorp colormap = png_ptr->palette;
+ const int do_background = trans != NULL &&
+ (output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
+ unsigned int i;
+
+ /* Just in case: */
+ if (trans == NULL)
+ num_trans = 0;
+
+ output_processing = PNG_CMAP_NONE;
+ data_encoding = E_FILE; /* Don't change from color-map indicies */
+ cmap_entries = png_ptr->num_palette;
+ if (cmap_entries > 256)
+ cmap_entries = 256;
+
+ if (cmap_entries > image->colormap_entries)
+ png_error(png_ptr, "palette color-map: too few entries");
+
+ for (i=0; i < cmap_entries; ++i)
+ {
+ if (do_background && i < num_trans && trans[i] < 255)
+ {
+ if (trans[i] == 0)
+ png_create_colormap_entry(display, i, back_r, back_g,
+ back_b, 0, output_encoding);
+
+ else
+ {
+ /* Must compose the PNG file color in the color-map entry
+ * on the sRGB color in 'back'.
+ */
+ png_create_colormap_entry(display, i,
+ png_colormap_compose(display, colormap[i].red, E_FILE,
+ trans[i], back_r, output_encoding),
+ png_colormap_compose(display, colormap[i].green, E_FILE,
+ trans[i], back_g, output_encoding),
+ png_colormap_compose(display, colormap[i].blue, E_FILE,
+ trans[i], back_b, output_encoding),
+ output_encoding == E_LINEAR ? trans[i] * 257U :
+ trans[i],
+ output_encoding);
+ }
+ }
+
+ else
+ png_create_colormap_entry(display, i, colormap[i].red,
+ colormap[i].green, colormap[i].blue,
+ i < num_trans ? trans[i] : 255U, E_FILE/*8-bit*/);
+ }
+
+ /* The PNG data may have indicies packed in fewer than 8 bits, it
+ * must be expanded if so.
+ */
+ if (png_ptr->bit_depth < 8)
+ png_set_packing(png_ptr);
+ }
+ break;
+
+ default:
+ png_error(png_ptr, "invalid PNG color type");
+ /*NOT REACHED*/
+ break;
+ }
+
+ /* Now deal with the output processing */
+ if (expand_tRNS && png_ptr->num_trans > 0 &&
+ (png_ptr->color_type & PNG_COLOR_MASK_ALPHA) == 0)
+ png_set_tRNS_to_alpha(png_ptr);
+
+ switch (data_encoding)
+ {
+ default:
+ png_error(png_ptr, "bad data option (internal error)");
+ break;
+
+ case E_sRGB:
+ /* Change to 8-bit sRGB */
+ png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
+ /* FALL THROUGH */
+
+ case E_FILE:
+ if (png_ptr->bit_depth > 8)
+ png_set_scale_16(png_ptr);
+ break;
+ }
+
+ if (cmap_entries > 256 || cmap_entries > image->colormap_entries)
+ png_error(png_ptr, "color map overflow (BAD internal error)");
+
+ image->colormap_entries = cmap_entries;
+
+ /* Double check using the recorded background index */
+ switch (output_processing)
+ {
+ case PNG_CMAP_NONE:
+ if (background_index != PNG_CMAP_NONE_BACKGROUND)
+ goto bad_background;
+ break;
+
+ case PNG_CMAP_GA:
+ if (background_index != PNG_CMAP_GA_BACKGROUND)
+ goto bad_background;
+ break;
+
+ case PNG_CMAP_TRANS:
+ if (background_index >= cmap_entries ||
+ background_index != PNG_CMAP_TRANS_BACKGROUND)
+ goto bad_background;
+ break;
+
+ case PNG_CMAP_RGB:
+ if (background_index != PNG_CMAP_RGB_BACKGROUND)
+ goto bad_background;
+ break;
+
+ case PNG_CMAP_RGB_ALPHA:
+ if (background_index != PNG_CMAP_RGB_ALPHA_BACKGROUND)
+ goto bad_background;
+ break;
+
+ default:
+ png_error(png_ptr, "bad processing option (internal error)");
+
+ bad_background:
+ png_error(png_ptr, "bad background index (internal error)");
+ }
+
+ display->colormap_processing = output_processing;
+
+ return 1/*ok*/;
+}
+
+/* The final part of the color-map read called from png_image_finish_read. */
+static int
+png_image_read_and_map(png_voidp argument)
+{
+ png_image_read_control *display = png_voidcast(png_image_read_control*,
+ argument);
+ png_imagep image = display->image;
+ png_structrp png_ptr = image->opaque->png_ptr;
+ int passes;
+
+ /* Called when the libpng data must be transformed into the color-mapped
+ * form. There is a local row buffer in display->local and this routine must
+ * do the interlace handling.
+ */
+ switch (png_ptr->interlaced)
+ {
+ case PNG_INTERLACE_NONE:
+ passes = 1;
+ break;
+
+ case PNG_INTERLACE_ADAM7:
+ passes = PNG_INTERLACE_ADAM7_PASSES;
+ break;
+
+ default:
+ passes = 0;
+ png_error(png_ptr, "unknown interlace type");
+ }
+
+ {
+ png_uint_32 height = image->height;
+ png_uint_32 width = image->width;
+ int proc = display->colormap_processing;
+ png_bytep first_row = png_voidcast(png_bytep, display->first_row);
+ ptrdiff_t step_row = display->row_bytes;
+ int pass;
+
+ for (pass = 0; pass < passes; ++pass)
+ {
+ unsigned int startx, stepx, stepy;
+ png_uint_32 y;
+
+ if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
+ {
+ /* The row may be empty for a short image: */
+ if (PNG_PASS_COLS(width, pass) == 0)
+ continue;
+
+ startx = PNG_PASS_START_COL(pass);
+ stepx = PNG_PASS_COL_OFFSET(pass);
+ y = PNG_PASS_START_ROW(pass);
+ stepy = PNG_PASS_ROW_OFFSET(pass);
+ }
+
+ else
+ {
+ y = 0;
+ startx = 0;
+ stepx = stepy = 1;
+ }
+
+ for (; y<height; y += stepy)
+ {
+ png_bytep inrow = png_voidcast(png_bytep, display->local_row);
+ png_bytep outrow = first_row + y * step_row;
+ png_const_bytep end_row = outrow + width;
+
+ /* Read read the libpng data into the temporary buffer. */
+ png_read_row(png_ptr, inrow, NULL);
+
+ /* Now process the row according to the processing option, note
+ * that the caller verifies that the format of the libpng output
+ * data is as required.
+ */
+ outrow += startx;
+ switch (proc)
+ {
+ case PNG_CMAP_GA:
+ for (; outrow < end_row; outrow += stepx)
+ {
+ /* The data is always in the PNG order */
+ unsigned int gray = *inrow++;
+ unsigned int alpha = *inrow++;
+ unsigned int entry;
+
+ /* NOTE: this code is copied as a comment in
+ * make_ga_colormap above. Please update the
+ * comment if you change this code!
+ */
+ if (alpha > 229) /* opaque */
+ {
+ entry = (231 * gray + 128) >> 8;
+ }
+ else if (alpha < 26) /* transparent */
+ {
+ entry = 231;
+ }
+ else /* partially opaque */
+ {
+ entry = 226 + 6 * PNG_DIV51(alpha) + PNG_DIV51(gray);
+ }
+
+ *outrow = (png_byte)entry;
+ }
+ break;
+
+ case PNG_CMAP_TRANS:
+ for (; outrow < end_row; outrow += stepx)
+ {
+ png_byte gray = *inrow++;
+ png_byte alpha = *inrow++;
+
+ if (alpha == 0)
+ *outrow = PNG_CMAP_TRANS_BACKGROUND;
+
+ else if (gray != PNG_CMAP_TRANS_BACKGROUND)
+ *outrow = gray;
+
+ else
+ *outrow = (png_byte)(PNG_CMAP_TRANS_BACKGROUND+1);
+ }
+ break;
+
+ case PNG_CMAP_RGB:
+ for (; outrow < end_row; outrow += stepx)
+ {
+ *outrow = PNG_RGB_INDEX(inrow[0], inrow[1], inrow[2]);
+ inrow += 3;
+ }
+ break;
+
+ case PNG_CMAP_RGB_ALPHA:
+ for (; outrow < end_row; outrow += stepx)
+ {
+ unsigned int alpha = inrow[3];
+
+ /* Because the alpha entries only hold alpha==0.5 values
+ * split the processing at alpha==0.25 (64) and 0.75
+ * (196).
+ */
+
+ if (alpha >= 196)
+ *outrow = PNG_RGB_INDEX(inrow[0], inrow[1],
+ inrow[2]);
+
+ else if (alpha < 64)
+ *outrow = PNG_CMAP_RGB_ALPHA_BACKGROUND;
+
+ else
+ {
+ /* Likewise there are three entries for each of r, g
+ * and b. We could select the entry by popcount on
+ * the top two bits on those architectures that
+ * support it, this is what the code below does,
+ * crudely.
+ */
+ unsigned int back_i = PNG_CMAP_RGB_ALPHA_BACKGROUND+1;
+
+ /* Here are how the values map:
+ *
+ * 0x00 .. 0x3f -> 0
+ * 0x40 .. 0xbf -> 1
+ * 0xc0 .. 0xff -> 2
+ *
+ * So, as above with the explicit alpha checks, the
+ * breakpoints are at 64 and 196.
+ */
+ if (inrow[0] & 0x80) back_i += 9; /* red */
+ if (inrow[0] & 0x40) back_i += 9;
+ if (inrow[0] & 0x80) back_i += 3; /* green */
+ if (inrow[0] & 0x40) back_i += 3;
+ if (inrow[0] & 0x80) back_i += 1; /* blue */
+ if (inrow[0] & 0x40) back_i += 1;
+
+ *outrow = (png_byte)back_i;
+ }
+
+ inrow += 4;
+ }
+ break;
+
+ default:
+ break;
+ }
+ }
+ }
+ }
+
+ return 1;
+}
+
+static int
+png_image_read_colormapped(png_voidp argument)
+{
+ png_image_read_control *display = png_voidcast(png_image_read_control*,
+ argument);
+ png_imagep image = display->image;
+ png_controlp control = image->opaque;
+ png_structrp png_ptr = control->png_ptr;
+ png_inforp info_ptr = control->info_ptr;
+
+ int passes = 0; /* As a flag */
+
+ PNG_SKIP_CHUNKS(png_ptr);
+
+ /* Update the 'info' structure and make sure the result is as required; first
+ * make sure to turn on the interlace handling if it will be required
+ * (because it can't be turned on *after* the call to png_read_update_info!)
+ */
+ if (display->colormap_processing == PNG_CMAP_NONE)
+ passes = png_set_interlace_handling(png_ptr);
+
+ png_read_update_info(png_ptr, info_ptr);
+
+ /* The expected output can be deduced from the colormap_processing option. */
+ switch (display->colormap_processing)
+ {
+ case PNG_CMAP_NONE:
+ /* Output must be one channel and one byte per pixel, the output
+ * encoding can be anything.
+ */
+ if ((info_ptr->color_type == PNG_COLOR_TYPE_PALETTE ||
+ info_ptr->color_type == PNG_COLOR_TYPE_GRAY) &&
+ info_ptr->bit_depth == 8)
+ break;
+
+ goto bad_output;
+
+ case PNG_CMAP_TRANS:
+ case PNG_CMAP_GA:
+ /* Output must be two channels and the 'G' one must be sRGB, the latter
+ * can be checked with an exact number because it should have been set
+ * to this number above!
+ */
+ if (info_ptr->color_type == PNG_COLOR_TYPE_GRAY_ALPHA &&
+ info_ptr->bit_depth == 8 &&
+ png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
+ image->colormap_entries == 256)
+ break;
+
+ goto bad_output;
+
+ case PNG_CMAP_RGB:
+ /* Output must be 8-bit sRGB encoded RGB */
+ if (info_ptr->color_type == PNG_COLOR_TYPE_RGB &&
+ info_ptr->bit_depth == 8 &&
+ png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
+ image->colormap_entries == 216)
+ break;
+
+ goto bad_output;
+
+ case PNG_CMAP_RGB_ALPHA:
+ /* Output must be 8-bit sRGB encoded RGBA */
+ if (info_ptr->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
+ info_ptr->bit_depth == 8 &&
+ png_ptr->screen_gamma == PNG_GAMMA_sRGB &&
+ image->colormap_entries == 244 /* 216 + 1 + 27 */)
+ break;
+
+ /* goto bad_output; */
+ /* FALL THROUGH */
+
+ default:
+ bad_output:
+ png_error(png_ptr, "bad color-map processing (internal error)");
+ }
+
+ /* Now read the rows. Do this here if it is possible to read directly into
+ * the output buffer, otherwise allocate a local row buffer of the maximum
+ * size libpng requires and call the relevant processing routine safely.
+ */
+ {
+ png_voidp first_row = display->buffer;
+ ptrdiff_t row_bytes = display->row_stride;
+
+ /* The following expression is designed to work correctly whether it gives
+ * a signed or an unsigned result.
+ */
+ if (row_bytes < 0)
+ {
+ char *ptr = png_voidcast(char*, first_row);
+ ptr += (image->height-1) * (-row_bytes);
+ first_row = png_voidcast(png_voidp, ptr);
+ }
+
+ display->first_row = first_row;
+ display->row_bytes = row_bytes;
+ }
+
+ if (passes == 0)
+ {
+ int result;
+ png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
+
+ display->local_row = row;
+ result = png_safe_execute(image, png_image_read_and_map, display);
+ display->local_row = NULL;
+ png_free(png_ptr, row);
+
+ return result;
+ }
+
+ else
+ {
+ png_alloc_size_t row_bytes = display->row_bytes;
+
+ while (--passes >= 0)
+ {
+ png_uint_32 y = image->height;
+ png_bytep row = png_voidcast(png_bytep, display->first_row);
+
+ while (y-- > 0)
+ {
+ png_read_row(png_ptr, row, NULL);
+ row += row_bytes;
+ }
+ }
+
+ return 1;
+ }
+}
+
+/* Just the row reading part of png_image_read. */
+static int
+png_image_read_composite(png_voidp argument)
+{
+ png_image_read_control *display = png_voidcast(png_image_read_control*,
+ argument);
+ png_imagep image = display->image;
+ png_structrp png_ptr = image->opaque->png_ptr;
+ int passes;
+
+ switch (png_ptr->interlaced)
+ {
+ case PNG_INTERLACE_NONE:
+ passes = 1;
+ break;
+
+ case PNG_INTERLACE_ADAM7:
+ passes = PNG_INTERLACE_ADAM7_PASSES;
+ break;
+
+ default:
+ passes = 0;
+ png_error(png_ptr, "unknown interlace type");
+ }
+
+ {
+ png_uint_32 height = image->height;
+ png_uint_32 width = image->width;
+ ptrdiff_t step_row = display->row_bytes;
+ unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;
+ int pass;
+
+ for (pass = 0; pass < passes; ++pass)
+ {
+ unsigned int startx, stepx, stepy;
+ png_uint_32 y;
+
+ if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
+ {
+ /* The row may be empty for a short image: */
+ if (PNG_PASS_COLS(width, pass) == 0)
+ continue;
+
+ startx = PNG_PASS_START_COL(pass) * channels;
+ stepx = PNG_PASS_COL_OFFSET(pass) * channels;
+ y = PNG_PASS_START_ROW(pass);
+ stepy = PNG_PASS_ROW_OFFSET(pass);
+ }
+
+ else
+ {
+ y = 0;
+ startx = 0;
+ stepx = channels;
+ stepy = 1;
+ }
+
+ for (; y<height; y += stepy)
+ {
+ png_bytep inrow = png_voidcast(png_bytep, display->local_row);
+ png_bytep outrow;
+ png_const_bytep end_row;
+
+ /* Read the row, which is packed: */
+ png_read_row(png_ptr, inrow, NULL);
+
+ outrow = png_voidcast(png_bytep, display->first_row);
+ outrow += y * step_row;
+ end_row = outrow + width * channels;
+
+ /* Now do the composition on each pixel in this row. */
+ outrow += startx;
+ for (; outrow < end_row; outrow += stepx)
+ {
+ png_byte alpha = inrow[channels];
+
+ if (alpha > 0) /* else no change to the output */
+ {
+ unsigned int c;
+
+ for (c=0; c<channels; ++c)
+ {
+ png_uint_32 component = inrow[c];
+
+ if (alpha < 255) /* else just use component */
+ {
+ /* This is PNG_OPTIMIZED_ALPHA, the component value
+ * is a linear 8-bit value. Combine this with the
+ * current outrow[c] value which is sRGB encoded.
+ * Arithmetic here is 16-bits to preserve the output
+ * values correctly.
+ */
+ component *= 257*255; /* =65535 */
+ component += (255-alpha)*png_sRGB_table[outrow[c]];
+
+ /* So 'component' is scaled by 255*65535 and is
+ * therefore appropriate for the sRGB to linear
+ * conversion table.
+ */
+ component = PNG_sRGB_FROM_LINEAR(component);
+ }
+
+ outrow[c] = (png_byte)component;
+ }
+ }
+
+ inrow += channels+1; /* components and alpha channel */
+ }
+ }
+ }
+ }
+
+ return 1;
+}
+
+/* The do_local_background case; called when all the following transforms are to
+ * be done:
+ *
+ * PNG_RGB_TO_GRAY
+ * PNG_COMPOSITE
+ * PNG_GAMMA
+ *
+ * This is a work-round for the fact that both the PNG_RGB_TO_GRAY and
+ * PNG_COMPOSITE code performs gamma correction, so we get double gamma
+ * correction. The fix-up is to prevent the PNG_COMPOSITE operation happening
+ * inside libpng, so this routine sees an 8 or 16-bit gray+alpha row and handles
+ * the removal or pre-multiplication of the alpha channel.
+ */
+static int
+png_image_read_background(png_voidp argument)
+{
+ png_image_read_control *display = png_voidcast(png_image_read_control*,
+ argument);
+ png_imagep image = display->image;
+ png_structrp png_ptr = image->opaque->png_ptr;
+ png_inforp info_ptr = image->opaque->info_ptr;
+ png_uint_32 height = image->height;
+ png_uint_32 width = image->width;
+ int pass, passes;
+
+ /* Double check the convoluted logic below. We expect to get here with
+ * libpng doing rgb to gray and gamma correction but background processing
+ * left to the png_image_read_background function. The rows libpng produce
+ * might be 8 or 16-bit but should always have two channels; gray plus alpha.
+ */
+ if ((png_ptr->transformations & PNG_RGB_TO_GRAY) == 0)
+ png_error(png_ptr, "lost rgb to gray");
+
+ if ((png_ptr->transformations & PNG_COMPOSE) != 0)
+ png_error(png_ptr, "unexpected compose");
+
+ if (png_get_channels(png_ptr, info_ptr) != 2)
+ png_error(png_ptr, "lost/gained channels");
+
+ /* Expect the 8-bit case to always remove the alpha channel */
+ if ((image->format & PNG_FORMAT_FLAG_LINEAR) == 0 &&
+ (image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
+ png_error(png_ptr, "unexpected 8-bit transformation");
+
+ switch (png_ptr->interlaced)
+ {
+ case PNG_INTERLACE_NONE:
+ passes = 1;
+ break;
+
+ case PNG_INTERLACE_ADAM7:
+ passes = PNG_INTERLACE_ADAM7_PASSES;
+ break;
+
+ default:
+ passes = 0;
+ png_error(png_ptr, "unknown interlace type");
+ }
+
+ switch (png_get_bit_depth(png_ptr, info_ptr))
+ {
+ default:
+ png_error(png_ptr, "unexpected bit depth");
+ break;
+
+ case 8:
+ /* 8-bit sRGB gray values with an alpha channel; the alpha channel is
+ * to be removed by composing on a backgroundi: either the row if
+ * display->background is NULL or display->background->green if not.
+ * Unlike the code above ALPHA_OPTIMIZED has *not* been done.
+ */
+ {
+ png_bytep first_row = png_voidcast(png_bytep, display->first_row);
+ ptrdiff_t step_row = display->row_bytes;
+
+ for (pass = 0; pass < passes; ++pass)
+ {
+ png_bytep row = png_voidcast(png_bytep,
+ display->first_row);
+ unsigned int startx, stepx, stepy;
+ png_uint_32 y;
+
+ if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
+ {
+ /* The row may be empty for a short image: */
+ if (PNG_PASS_COLS(width, pass) == 0)
+ continue;
+
+ startx = PNG_PASS_START_COL(pass);
+ stepx = PNG_PASS_COL_OFFSET(pass);
+ y = PNG_PASS_START_ROW(pass);
+ stepy = PNG_PASS_ROW_OFFSET(pass);
+ }
+
+ else
+ {
+ y = 0;
+ startx = 0;
+ stepx = stepy = 1;
+ }
+
+ if (display->background == NULL)
+ {
+ for (; y<height; y += stepy)
+ {
+ png_bytep inrow = png_voidcast(png_bytep,
+ display->local_row);
+ png_bytep outrow = first_row + y * step_row;
+ png_const_bytep end_row = outrow + width;
+
+ /* Read the row, which is packed: */
+ png_read_row(png_ptr, inrow, NULL);
+
+ /* Now do the composition on each pixel in this row. */
+ outrow += startx;
+ for (; outrow < end_row; outrow += stepx)
+ {
+ png_byte alpha = inrow[1];
+
+ if (alpha > 0) /* else no change to the output */
+ {
+ png_uint_32 component = inrow[0];
+
+ if (alpha < 255) /* else just use component */
+ {
+ /* Since PNG_OPTIMIZED_ALPHA was not set it is
+ * necessary to invert the sRGB transfer
+ * function and multiply the alpha out.
+ */
+ component = png_sRGB_table[component] * alpha;
+ component += png_sRGB_table[outrow[0]] *
+ (255-alpha);
+ component = PNG_sRGB_FROM_LINEAR(component);
+ }
+
+ outrow[0] = (png_byte)component;
+ }
+
+ inrow += 2; /* gray and alpha channel */
+ }
+ }
+ }
+
+ else /* constant background value */
+ {
+ png_byte background8 = display->background->green;
+ png_uint_16 background = png_sRGB_table[background8];
+
+ for (; y<height; y += stepy)
+ {
+ png_bytep inrow = png_voidcast(png_bytep,
+ display->local_row);
+ png_bytep outrow = first_row + y * step_row;
+ png_const_bytep end_row = outrow + width;
+
+ /* Read the row, which is packed: */
+ png_read_row(png_ptr, inrow, NULL);
+
+ /* Now do the composition on each pixel in this row. */
+ outrow += startx;
+ for (; outrow < end_row; outrow += stepx)
+ {
+ png_byte alpha = inrow[1];
+
+ if (alpha > 0) /* else use background */
+ {
+ png_uint_32 component = inrow[0];
+
+ if (alpha < 255) /* else just use component */
+ {
+ component = png_sRGB_table[component] * alpha;
+ component += background * (255-alpha);
+ component = PNG_sRGB_FROM_LINEAR(component);
+ }
+
+ outrow[0] = (png_byte)component;
+ }
+
+ else
+ outrow[0] = background8;
+
+ inrow += 2; /* gray and alpha channel */
+ }
+
+ row += display->row_bytes;
+ }
+ }
+ }
+ }
+ break;
+
+ case 16:
+ /* 16-bit linear with pre-multiplied alpha; the pre-multiplication must
+ * still be done and, maybe, the alpha channel removed. This code also
+ * handles the alpha-first option.
+ */
+ {
+ png_uint_16p first_row = png_voidcast(png_uint_16p,
+ display->first_row);
+ /* The division by two is safe because the caller passed in a
+ * stride which was multiplied by 2 (below) to get row_bytes.
+ */
+ ptrdiff_t step_row = display->row_bytes / 2;
+ int preserve_alpha = (image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
+ unsigned int outchannels = 1+preserve_alpha;
+ int swap_alpha = 0;
+
+ if (preserve_alpha && (image->format & PNG_FORMAT_FLAG_AFIRST))
+ swap_alpha = 1;
+
+ for (pass = 0; pass < passes; ++pass)
+ {
+ unsigned int startx, stepx, stepy;
+ png_uint_32 y;
+
+ /* The 'x' start and step are adjusted to output components here.
+ */
+ if (png_ptr->interlaced == PNG_INTERLACE_ADAM7)
+ {
+ /* The row may be empty for a short image: */
+ if (PNG_PASS_COLS(width, pass) == 0)
+ continue;
+
+ startx = PNG_PASS_START_COL(pass) * outchannels;
+ stepx = PNG_PASS_COL_OFFSET(pass) * outchannels;
+ y = PNG_PASS_START_ROW(pass);
+ stepy = PNG_PASS_ROW_OFFSET(pass);
+ }
+
+ else
+ {
+ y = 0;
+ startx = 0;
+ stepx = outchannels;
+ stepy = 1;
+ }
+
+ for (; y<height; y += stepy)
+ {
+ png_const_uint_16p inrow;
+ png_uint_16p outrow = first_row + y*step_row;
+ png_uint_16p end_row = outrow + width * outchannels;
+
+ /* Read the row, which is packed: */
+ png_read_row(png_ptr, png_voidcast(png_bytep,
+ display->local_row), NULL);
+ inrow = png_voidcast(png_const_uint_16p, display->local_row);
+
+ /* Now do the pre-multiplication on each pixel in this row.
+ */
+ outrow += startx;
+ for (; outrow < end_row; outrow += stepx)
+ {
+ png_uint_32 component = inrow[0];
+ png_uint_16 alpha = inrow[1];
+
+ if (alpha > 0) /* else 0 */
+ {
+ if (alpha < 65535) /* else just use component */
+ {
+ component *= alpha;
+ component += 32767;
+ component /= 65535;
+ }
+ }
+
+ else
+ component = 0;
+
+ outrow[swap_alpha] = (png_uint_16)component;
+ if (preserve_alpha)
+ outrow[1 ^ swap_alpha] = alpha;
+
+ inrow += 2; /* components and alpha channel */
+ }
+ }
+ }
+ }
+ break;
+ }
+
+ return 1;
+}
+
+/* The guts of png_image_finish_read as a png_safe_execute callback. */
+static int
+png_image_read_direct(png_voidp argument)
+{
+ png_image_read_control *display = png_voidcast(png_image_read_control*,
+ argument);
+ png_imagep image = display->image;
+ png_structrp png_ptr = image->opaque->png_ptr;
+ png_inforp info_ptr = image->opaque->info_ptr;
+
+ png_uint_32 format = image->format;
+ int linear = (format & PNG_FORMAT_FLAG_LINEAR) != 0;
+ int do_local_compose = 0;
+ int do_local_background = 0; /* to avoid double gamma correction bug */
+ int passes = 0;
+
+ /* Add transforms to ensure the correct output format is produced then check
+ * that the required implementation support is there. Always expand; always
+ * need 8 bits minimum, no palette and expanded tRNS.
+ */
+ png_set_expand(png_ptr);
+
+ /* Now check the format to see if it was modified. */
+ {
+ png_uint_32 base_format = png_image_format(png_ptr) &
+ ~PNG_FORMAT_FLAG_COLORMAP /* removed by png_set_expand */;
+ png_uint_32 change = format ^ base_format;
+ png_fixed_point output_gamma;
+ int mode; /* alpha mode */
+
+ /* Do this first so that we have a record if rgb to gray is happening. */
+ if (change & PNG_FORMAT_FLAG_COLOR)
+ {
+ /* gray<->color transformation required. */
+ if (format & PNG_FORMAT_FLAG_COLOR)
+ png_set_gray_to_rgb(png_ptr);
+
+ else
+ {
+ /* libpng can't do both rgb to gray and
+ * background/pre-multiplication if there is also significant gamma
+ * correction, because both operations require linear colors and
+ * the code only supports one transform doing the gamma correction.
+ * Handle this by doing the pre-multiplication or background
+ * operation in this code, if necessary.
+ *
+ * TODO: fix this by rewriting pngrtran.c (!)
+ *
+ * For the moment (given that fixing this in pngrtran.c is an
+ * enormous change) 'do_local_background' is used to indicate that
+ * the problem exists.
+ */
+ if (base_format & PNG_FORMAT_FLAG_ALPHA)
+ do_local_background = 1/*maybe*/;
+
+ png_set_rgb_to_gray_fixed(png_ptr, PNG_ERROR_ACTION_NONE,
+ PNG_RGB_TO_GRAY_DEFAULT, PNG_RGB_TO_GRAY_DEFAULT);
+ }
+
+ change &= ~PNG_FORMAT_FLAG_COLOR;
+ }
+
+ /* Set the gamma appropriately, linear for 16-bit input, sRGB otherwise.
+ */
+ {
+ png_fixed_point input_gamma_default;
+
+ if ((base_format & PNG_FORMAT_FLAG_LINEAR) &&
+ (image->flags & PNG_IMAGE_FLAG_16BIT_sRGB) == 0)
+ input_gamma_default = PNG_GAMMA_LINEAR;
+ else
+ input_gamma_default = PNG_DEFAULT_sRGB;
+
+ /* Call png_set_alpha_mode to set the default for the input gamma; the
+ * output gamma is set by a second call below.
+ */
+ png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, input_gamma_default);
+ }
+
+ if (linear)
+ {
+ /* If there *is* an alpha channel in the input it must be multiplied
+ * out; use PNG_ALPHA_STANDARD, otherwise just use PNG_ALPHA_PNG.
+ */
+ if (base_format & PNG_FORMAT_FLAG_ALPHA)
+ mode = PNG_ALPHA_STANDARD; /* associated alpha */
+
+ else
+ mode = PNG_ALPHA_PNG;
+
+ output_gamma = PNG_GAMMA_LINEAR;
+ }
+
+ else
+ {
+ mode = PNG_ALPHA_PNG;
+ output_gamma = PNG_DEFAULT_sRGB;
+ }
+
+ /* If 'do_local_background' is set check for the presence of gamma
+ * correction; this is part of the work-round for the libpng bug
+ * described above.
+ *
+ * TODO: fix libpng and remove this.
+ */
+ if (do_local_background)
+ {
+ png_fixed_point gtest;
+
+ /* This is 'png_gamma_threshold' from pngrtran.c; the test used for
+ * gamma correction, the screen gamma hasn't been set on png_struct
+ * yet; it's set below. png_struct::gamma, however, is set to the
+ * final value.
+ */
+ if (png_muldiv(>est, output_gamma, png_ptr->colorspace.gamma,
+ PNG_FP_1) && !png_gamma_significant(gtest))
+ do_local_background = 0;
+
+ else if (mode == PNG_ALPHA_STANDARD)
+ {
+ do_local_background = 2/*required*/;
+ mode = PNG_ALPHA_PNG; /* prevent libpng doing it */
+ }
+
+ /* else leave as 1 for the checks below */
+ }
+
+ /* If the bit-depth changes then handle that here. */
+ if (change & PNG_FORMAT_FLAG_LINEAR)
+ {
+ if (linear /*16-bit output*/)
+ png_set_expand_16(png_ptr);
+
+ else /* 8-bit output */
+ png_set_scale_16(png_ptr);
+
+ change &= ~PNG_FORMAT_FLAG_LINEAR;
+ }
+
+ /* Now the background/alpha channel changes. */
+ if (change & PNG_FORMAT_FLAG_ALPHA)
+ {
+ /* Removing an alpha channel requires composition for the 8-bit
+ * formats; for the 16-bit it is already done, above, by the
+ * pre-multiplication and the channel just needs to be stripped.
+ */
+ if (base_format & PNG_FORMAT_FLAG_ALPHA)
+ {
+ /* If RGB->gray is happening the alpha channel must be left and the
+ * operation completed locally.
+ *
+ * TODO: fix libpng and remove this.
+ */
+ if (do_local_background)
+ do_local_background = 2/*required*/;
+
+ /* 16-bit output: just remove the channel */
+ else if (linear) /* compose on black (well, pre-multiply) */
+ png_set_strip_alpha(png_ptr);
+
+ /* 8-bit output: do an appropriate compose */
+ else if (display->background != NULL)
+ {
+ png_color_16 c;
+
+ c.index = 0; /*unused*/
+ c.red = display->background->red;
+ c.green = display->background->green;
+ c.blue = display->background->blue;
+ c.gray = display->background->green;
+
+ /* This is always an 8-bit sRGB value, using the 'green' channel
+ * for gray is much better than calculating the luminance here;
+ * we can get off-by-one errors in that calculation relative to
+ * the app expectations and that will show up in transparent
+ * pixels.
+ */
+ png_set_background_fixed(png_ptr, &c,
+ PNG_BACKGROUND_GAMMA_SCREEN, 0/*need_expand*/,
+ 0/*gamma: not used*/);
+ }
+
+ else /* compose on row: implemented below. */
+ {
+ do_local_compose = 1;
+ /* This leaves the alpha channel in the output, so it has to be
+ * removed by the code below. Set the encoding to the 'OPTIMIZE'
+ * one so the code only has to hack on the pixels that require
+ * composition.
+ */
+ mode = PNG_ALPHA_OPTIMIZED;
+ }
+ }
+
+ else /* output needs an alpha channel */
+ {
+ /* This is tricky because it happens before the swap operation has
+ * been accomplished; however, the swap does *not* swap the added
+ * alpha channel (weird API), so it must be added in the correct
+ * place.
+ */
+ png_uint_32 filler; /* opaque filler */
+ int where;
+
+ if (linear)
+ filler = 65535;
+
+ else
+ filler = 255;
+
+# ifdef PNG_FORMAT_AFIRST_SUPPORTED
+ if (format & PNG_FORMAT_FLAG_AFIRST)
+ {
+ where = PNG_FILLER_BEFORE;
+ change &= ~PNG_FORMAT_FLAG_AFIRST;
+ }
+
+ else
+# endif
+ where = PNG_FILLER_AFTER;
+
+ png_set_add_alpha(png_ptr, filler, where);
+ }
+
+ /* This stops the (irrelevant) call to swap_alpha below. */
+ change &= ~PNG_FORMAT_FLAG_ALPHA;
+ }
+
+ /* Now set the alpha mode correctly; this is always done, even if there is
+ * no alpha channel in either the input or the output because it correctly
+ * sets the output gamma.
+ */
+ png_set_alpha_mode_fixed(png_ptr, mode, output_gamma);
+
+# ifdef PNG_FORMAT_BGR_SUPPORTED
+ if (change & PNG_FORMAT_FLAG_BGR)
+ {
+ /* Check only the output format; PNG is never BGR; don't do this if
+ * the output is gray, but fix up the 'format' value in that case.
+ */
+ if (format & PNG_FORMAT_FLAG_COLOR)
+ png_set_bgr(png_ptr);
+
+ else
+ format &= ~PNG_FORMAT_FLAG_BGR;
+
+ change &= ~PNG_FORMAT_FLAG_BGR;
+ }
+# endif
+
+# ifdef PNG_FORMAT_AFIRST_SUPPORTED
+ if (change & PNG_FORMAT_FLAG_AFIRST)
+ {
+ /* Only relevant if there is an alpha channel - it's particularly
+ * important to handle this correctly because do_local_compose may
+ * be set above and then libpng will keep the alpha channel for this
+ * code to remove.
+ */
+ if (format & PNG_FORMAT_FLAG_ALPHA)
+ {
+ /* Disable this if doing a local background,
+ * TODO: remove this when local background is no longer required.
+ */
+ if (do_local_background != 2)
+ png_set_swap_alpha(png_ptr);
+ }
+
+ else
+ format &= ~PNG_FORMAT_FLAG_AFIRST;
+
+ change &= ~PNG_FORMAT_FLAG_AFIRST;
+ }
+# endif
+
+ /* If the *output* is 16-bit then we need to check for a byte-swap on this
+ * architecture.
+ */
+ if (linear)
+ {
+ PNG_CONST png_uint_16 le = 0x0001;
+
+ if (*(png_const_bytep)&le)
+ png_set_swap(png_ptr);
+ }
+
+ /* If change is not now 0 some transformation is missing - error out. */
+ if (change)
+ png_error(png_ptr, "png_read_image: unsupported transformation");
+ }
+
+ PNG_SKIP_CHUNKS(png_ptr);
+
+ /* Update the 'info' structure and make sure the result is as required; first
+ * make sure to turn on the interlace handling if it will be required
+ * (because it can't be turned on *after* the call to png_read_update_info!)
+ *
+ * TODO: remove the do_local_background fixup below.
+ */
+ if (!do_local_compose && do_local_background != 2)
+ passes = png_set_interlace_handling(png_ptr);
+
+ png_read_update_info(png_ptr, info_ptr);
+
+ {
+ png_uint_32 info_format = 0;
+
+ if (info_ptr->color_type & PNG_COLOR_MASK_COLOR)
+ info_format |= PNG_FORMAT_FLAG_COLOR;
+
+ if (info_ptr->color_type & PNG_COLOR_MASK_ALPHA)
+ {
+ /* do_local_compose removes this channel below. */
+ if (!do_local_compose)
+ {
+ /* do_local_background does the same if required. */
+ if (do_local_background != 2 ||
+ (format & PNG_FORMAT_FLAG_ALPHA) != 0)
+ info_format |= PNG_FORMAT_FLAG_ALPHA;
+ }
+ }
+
+ else if (do_local_compose) /* internal error */
+ png_error(png_ptr, "png_image_read: alpha channel lost");
+
+ if (info_ptr->bit_depth == 16)
+ info_format |= PNG_FORMAT_FLAG_LINEAR;
+
+# ifdef PNG_FORMAT_BGR_SUPPORTED
+ if (png_ptr->transformations & PNG_BGR)
+ info_format |= PNG_FORMAT_FLAG_BGR;
+# endif
+
+# ifdef PNG_FORMAT_AFIRST_SUPPORTED
+ if (do_local_background == 2)
+ {
+ if (format & PNG_FORMAT_FLAG_AFIRST)
+ info_format |= PNG_FORMAT_FLAG_AFIRST;
+ }
+
+ if ((png_ptr->transformations & PNG_SWAP_ALPHA) != 0 ||
+ ((png_ptr->transformations & PNG_ADD_ALPHA) != 0 &&
+ (png_ptr->flags & PNG_FLAG_FILLER_AFTER) == 0))
+ {
+ if (do_local_background == 2)
+ png_error(png_ptr, "unexpected alpha swap transformation");
+
+ info_format |= PNG_FORMAT_FLAG_AFIRST;
+ }
+# endif
+
+ /* This is actually an internal error. */
+ if (info_format != format)
+ png_error(png_ptr, "png_read_image: invalid transformations");
+ }
+
+ /* Now read the rows. If do_local_compose is set then it is necessary to use
+ * a local row buffer. The output will be GA, RGBA or BGRA and must be
+ * converted to G, RGB or BGR as appropriate. The 'local_row' member of the
+ * display acts as a flag.
+ */
+ {
+ png_voidp first_row = display->buffer;
+ ptrdiff_t row_bytes = display->row_stride;
+
+ if (linear)
+ row_bytes *= 2;
+
+ /* The following expression is designed to work correctly whether it gives
+ * a signed or an unsigned result.
+ */
+ if (row_bytes < 0)
+ {
+ char *ptr = png_voidcast(char*, first_row);
+ ptr += (image->height-1) * (-row_bytes);
+ first_row = png_voidcast(png_voidp, ptr);
+ }
+
+ display->first_row = first_row;
+ display->row_bytes = row_bytes;
+ }
+
+ if (do_local_compose)
+ {
+ int result;
+ png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
+
+ display->local_row = row;
+ result = png_safe_execute(image, png_image_read_composite, display);
+ display->local_row = NULL;
+ png_free(png_ptr, row);
+
+ return result;
+ }
+
+ else if (do_local_background == 2)
+ {
+ int result;
+ png_voidp row = png_malloc(png_ptr, png_get_rowbytes(png_ptr, info_ptr));
+
+ display->local_row = row;
+ result = png_safe_execute(image, png_image_read_background, display);
+ display->local_row = NULL;
+ png_free(png_ptr, row);
+
+ return result;
+ }
+
+ else
+ {
+ png_alloc_size_t row_bytes = display->row_bytes;
+
+ while (--passes >= 0)
+ {
+ png_uint_32 y = image->height;
+ png_bytep row = png_voidcast(png_bytep, display->first_row);
+
+ while (y-- > 0)
+ {
+ png_read_row(png_ptr, row, NULL);
+ row += row_bytes;
+ }
+ }
+
+ return 1;
+ }
+}
+
+int PNGAPI
+png_image_finish_read(png_imagep image, png_const_colorp background,
+ void *buffer, png_int_32 row_stride, void *colormap)
+{
+ if (image != NULL && image->version == PNG_IMAGE_VERSION)
+ {
+ png_uint_32 check;
+
+ if (row_stride == 0)
+ row_stride = PNG_IMAGE_ROW_STRIDE(*image);
+
+ if (row_stride < 0)
+ check = -row_stride;
+
+ else
+ check = row_stride;
+
+ if (image->opaque != NULL && buffer != NULL &&
+ check >= PNG_IMAGE_ROW_STRIDE(*image))
+ {
+ if ((image->format & PNG_FORMAT_FLAG_COLORMAP) == 0 ||
+ (image->colormap_entries > 0 && colormap != NULL))
+ {
+ int result;
+ png_image_read_control display;
+
+ memset(&display, 0, (sizeof display));
+ display.image = image;
+ display.buffer = buffer;
+ display.row_stride = row_stride;
+ display.colormap = colormap;
+ display.background = background;
+ display.local_row = NULL;
+
+ /* Choose the correct 'end' routine; for the color-map case all the
+ * setup has already been done.
+ */
+ if (image->format & PNG_FORMAT_FLAG_COLORMAP)
+ result =
+ png_safe_execute(image, png_image_read_colormap, &display) &&
+ png_safe_execute(image, png_image_read_colormapped, &display);
+
+ else
+ result =
+ png_safe_execute(image, png_image_read_direct, &display);
+
+ png_image_free(image);
+ return result;
+ }
+
+ else
+ return png_image_error(image,
+ "png_image_finish_read[color-map]: no color-map");
+ }
+
+ else
+ return png_image_error(image,
+ "png_image_finish_read: invalid argument");
+ }
+
+ else if (image != NULL)
+ return png_image_error(image,
+ "png_image_finish_read: damaged PNG_IMAGE_VERSION");
+
+ return 0;
+}
+
+#endif /* PNG_SIMPLIFIED_READ_SUPPORTED */
+#endif /* PNG_READ_SUPPORTED */
projects / wxWidgets.git / blobdiff