+ case 1:
+ gray *= 0xff;
+ trans_gray *= 0xff;
+ break;
+
+ case 2:
+ gray *= 0x55;
+ trans_gray *= 0x55;
+ break;
+
+ case 4:
+ gray *= 0x11;
+ trans_gray *= 0x11;
+ break;
+
+ default:
+
+ case 8:
+ /* Already 8 bits, fall through */
+
+ case 16:
+ /* Already a full 16 bits */
+ break;
+ }
+
+ png_ptr->background.red = png_ptr->background.green =
+ png_ptr->background.blue = (png_uint_16)gray;
+
+ if (!(png_ptr->transformations & PNG_EXPAND_tRNS))
+ {
+ png_ptr->trans_color.red = png_ptr->trans_color.green =
+ png_ptr->trans_color.blue = (png_uint_16)trans_gray;
+ }
+ }
+ } /* background expand and (therefore) no alpha association. */
+#endif /* PNG_READ_EXPAND_SUPPORTED && PNG_READ_BACKGROUND_SUPPORTED */
+}
+
+void /* PRIVATE */
+png_init_read_transformations(png_structp png_ptr)
+{
+ png_debug(1, "in png_init_read_transformations");
+
+ /* This internal function is called from png_read_start_row in pngrutil.c
+ * and it is called before the 'rowbytes' calculation is done, so the code
+ * in here can change or update the transformations flags.
+ *
+ * First do updates that do not depend on the details of the PNG image data
+ * being processed.
+ */
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+ /* Prior to 1.5.4 these tests were performed from png_set_gamma, 1.5.4 adds
+ * png_set_alpha_mode and this is another source for a default file gamma so
+ * the test needs to be performed later - here. In addition prior to 1.5.4
+ * the tests were repeated for the PALETTE color type here - this is no
+ * longer necessary (and doesn't seem to have been necessary before.)
+ */
+ {
+ /* The following temporary indicates if overall gamma correction is
+ * required.
+ */
+ int gamma_correction = 0;
+
+ if (png_ptr->gamma != 0) /* has been set */
+ {
+ if (png_ptr->screen_gamma != 0) /* screen set too */
+ gamma_correction = png_gamma_threshold(png_ptr->gamma,
+ png_ptr->screen_gamma);
+
+ else
+ /* Assume the output matches the input; a long time default behavior
+ * of libpng, although the standard has nothing to say about this.
+ */
+ png_ptr->screen_gamma = png_reciprocal(png_ptr->gamma);
+ }
+
+ else if (png_ptr->screen_gamma != 0)
+ /* The converse - assume the file matches the screen, note that this
+ * perhaps undesireable default can (from 1.5.4) be changed by calling
+ * png_set_alpha_mode (even if the alpha handling mode isn't required
+ * or isn't changed from the default.)
+ */
+ png_ptr->gamma = png_reciprocal(png_ptr->screen_gamma);
+
+ else /* neither are set */
+ /* Just in case the following prevents any processing - file and screen
+ * are both assumed to be linear and there is no way to introduce a
+ * third gamma value other than png_set_background with 'UNIQUE', and,
+ * prior to 1.5.4
+ */
+ png_ptr->screen_gamma = png_ptr->gamma = PNG_FP_1;
+
+ /* Now turn the gamma transformation on or off as appropriate. Notice
+ * that PNG_GAMMA just refers to the file->screen correction. Alpha
+ * composition may independently cause gamma correction because it needs
+ * linear data (e.g. if the file has a gAMA chunk but the screen gamma
+ * hasn't been specified.) In any case this flag may get turned off in
+ * the code immediately below if the transform can be handled outside the
+ * row loop.
+ */
+ if (gamma_correction)
+ png_ptr->transformations |= PNG_GAMMA;
+
+ else
+ png_ptr->transformations &= ~PNG_GAMMA;
+ }
+#endif
+
+ /* Certain transformations have the effect of preventing other
+ * transformations that happen afterward in png_do_read_transformations,
+ * resolve the interdependencies here. From the code of
+ * png_do_read_transformations the order is:
+ *
+ * 1) PNG_EXPAND (including PNG_EXPAND_tRNS)
+ * 2) PNG_STRIP_ALPHA (if no compose)
+ * 3) PNG_RGB_TO_GRAY
+ * 4) PNG_GRAY_TO_RGB iff !PNG_BACKGROUND_IS_GRAY
+ * 5) PNG_COMPOSE
+ * 6) PNG_GAMMA
+ * 7) PNG_STRIP_ALPHA (if compose)
+ * 8) PNG_ENCODE_ALPHA
+ * 9) PNG_SCALE_16_TO_8
+ * 10) PNG_16_TO_8
+ * 11) PNG_QUANTIZE (converts to palette)
+ * 12) PNG_EXPAND_16
+ * 13) PNG_GRAY_TO_RGB iff PNG_BACKGROUND_IS_GRAY
+ * 14) PNG_INVERT_MONO
+ * 15) PNG_SHIFT
+ * 16) PNG_PACK
+ * 17) PNG_BGR
+ * 18) PNG_PACKSWAP
+ * 19) PNG_FILLER (includes PNG_ADD_ALPHA)
+ * 20) PNG_INVERT_ALPHA
+ * 21) PNG_SWAP_ALPHA
+ * 22) PNG_SWAP_BYTES
+ * 23) PNG_USER_TRANSFORM [must be last]
+ */
+#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
+ if ((png_ptr->transformations & PNG_STRIP_ALPHA) &&
+ !(png_ptr->transformations & PNG_COMPOSE))
+ {
+ /* Stripping the alpha channel happens immediately after the 'expand'
+ * transformations, before all other transformation, so it cancels out
+ * the alpha handling. It has the side effect negating the effect of
+ * PNG_EXPAND_tRNS too:
+ */
+ png_ptr->transformations &= ~(PNG_BACKGROUND_EXPAND | PNG_ENCODE_ALPHA |
+ PNG_EXPAND_tRNS);
+ png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+
+ /* Kill the tRNS chunk itself too. Prior to 1.5.4 this did not happen
+ * so transparency information would remain just so long as it wasn't
+ * expanded. This produces unexpected API changes if the set of things
+ * that do PNG_EXPAND_tRNS changes (perfectly possible given the
+ * documentation - which says ask for what you want, accept what you
+ * get.) This makes the behavior consistent from 1.5.4:
+ */
+ png_ptr->num_trans = 0;
+ }
+#endif /* STRIP_ALPHA supported, no COMPOSE */
+
+#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
+ /* If the screen gamma is about 1.0 then the OPTIMIZE_ALPHA and ENCODE_ALPHA
+ * settings will have no effect.
+ */
+ if (!png_gamma_significant(png_ptr->screen_gamma))
+ {
+ png_ptr->transformations &= ~PNG_ENCODE_ALPHA;
+ png_ptr->flags &= ~PNG_FLAG_OPTIMIZE_ALPHA;
+ }
+#endif
+
+#if defined(PNG_READ_EXPAND_SUPPORTED) && \
+ defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+ defined(PNG_READ_GRAY_TO_RGB_SUPPORTED)
+ /* Detect gray background and attempt to enable optimization for
+ * gray --> RGB case.
+ *
+ * Note: if PNG_BACKGROUND_EXPAND is set and color_type is either RGB or
+ * RGB_ALPHA (in which case need_expand is superfluous anyway), the
+ * background color might actually be gray yet not be flagged as such.
+ * This is not a problem for the current code, which uses
+ * PNG_BACKGROUND_IS_GRAY only to decide when to do the
+ * png_do_gray_to_rgb() transformation.
+ *
+ * TODO: this code needs to be revised to avoid the complexity and
+ * interdependencies. The color type of the background should be recorded in
+ * png_set_background, along with the bit depth, then the code has a record
+ * of exactly what color space the background is currently in.
+ */
+ if (png_ptr->transformations & PNG_BACKGROUND_EXPAND)
+ {
+ /* PNG_BACKGROUND_EXPAND: the background is in the file color space, so if
+ * the file was grayscale the background value is gray.
+ */
+ if (!(png_ptr->color_type & PNG_COLOR_MASK_COLOR))
+ png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+ }
+
+ else if (png_ptr->transformations & PNG_COMPOSE)
+ {
+ /* PNG_COMPOSE: png_set_background was called with need_expand false,
+ * so the color is in the color space of the output or png_set_alpha_mode
+ * was called and the color is black. Ignore RGB_TO_GRAY because that
+ * happens before GRAY_TO_RGB.
+ */
+ if (png_ptr->transformations & PNG_GRAY_TO_RGB)
+ {
+ if (png_ptr->background.red == png_ptr->background.green &&
+ png_ptr->background.red == png_ptr->background.blue)
+ {
+ png_ptr->mode |= PNG_BACKGROUND_IS_GRAY;
+ png_ptr->background.gray = png_ptr->background.red;
+ }
+ }
+ }
+#endif /* PNG_READ_GRAY_TO_RGB_SUPPORTED (etc) */
+
+ /* For indexed PNG data (PNG_COLOR_TYPE_PALETTE) many of the transformations
+ * can be performed directly on the palette, and some (such as rgb to gray)
+ * can be optimized inside the palette. This is particularly true of the
+ * composite (background and alpha) stuff, which can be pretty much all done
+ * in the palette even if the result is expanded to RGB or gray afterward.
+ *
+ * NOTE: this is Not Yet Implemented, the code behaves as in 1.5.1 and
+ * earlier and the palette stuff is actually handled on the first row. This
+ * leads to the reported bug that the palette returned by png_get_PLTE is not
+ * updated.
+ */
+ if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+ png_init_palette_transformations(png_ptr);
+
+ else
+ png_init_rgb_transformations(png_ptr);
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+ defined(PNG_READ_EXPAND_16_SUPPORTED)
+ if ((png_ptr->transformations & PNG_EXPAND_16) &&
+ (png_ptr->transformations & PNG_COMPOSE) &&
+ !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+ png_ptr->bit_depth != 16)
+ {
+ /* TODO: fix this. Because the expand_16 operation is after the compose
+ * handling the background color must be 8, not 16, bits deep, but the
+ * application will supply a 16-bit value so reduce it here.
+ *
+ * The PNG_BACKGROUND_EXPAND code above does not expand to 16 bits at
+ * present, so that case is ok (until do_expand_16 is moved.)
+ *
+ * NOTE: this discards the low 16 bits of the user supplied background
+ * color, but until expand_16 works properly there is no choice!
+ */
+# define CHOP(x) (x)=((png_uint_16)(((png_uint_32)(x)*255+32895) >> 16))
+ CHOP(png_ptr->background.red);
+ CHOP(png_ptr->background.green);
+ CHOP(png_ptr->background.blue);
+ CHOP(png_ptr->background.gray);
+# undef CHOP
+ }
+#endif /* PNG_READ_BACKGROUND_SUPPORTED && PNG_READ_EXPAND_16_SUPPORTED */
+
+#if defined(PNG_READ_BACKGROUND_SUPPORTED) && \
+ (defined(PNG_READ_SCALE_16_TO_8_SUPPORTED) || \
+ defined(PNG_READ_STRIP_16_TO_8_SUPPORTED))
+ if ((png_ptr->transformations & (PNG_16_TO_8|PNG_SCALE_16_TO_8)) &&
+ (png_ptr->transformations & PNG_COMPOSE) &&
+ !(png_ptr->transformations & PNG_BACKGROUND_EXPAND) &&
+ png_ptr->bit_depth == 16)
+ {
+ /* On the other hand, if a 16-bit file is to be reduced to 8-bits per
+ * component this will also happen after PNG_COMPOSE and so the background
+ * color must be pre-expanded here.
+ *
+ * TODO: fix this too.
+ */
+ png_ptr->background.red = (png_uint_16)(png_ptr->background.red * 257);
+ png_ptr->background.green =
+ (png_uint_16)(png_ptr->background.green * 257);
+ png_ptr->background.blue = (png_uint_16)(png_ptr->background.blue * 257);
+ png_ptr->background.gray = (png_uint_16)(png_ptr->background.gray * 257);
+ }
+#endif
+
+ /* NOTE: below 'PNG_READ_ALPHA_MODE_SUPPORTED' is presumed to also enable the
+ * background support (see the comments in scripts/pnglibconf.dfa), this
+ * allows pre-multiplication of the alpha channel to be implemented as
+ * compositing on black. This is probably sub-optimal and has been done in
+ * 1.5.4 betas simply to enable external critique and testing (i.e. to
+ * implement the new API quickly, without lots of internal changes.)
+ */
+
+#ifdef PNG_READ_GAMMA_SUPPORTED
+# ifdef PNG_READ_BACKGROUND_SUPPORTED
+ /* Includes ALPHA_MODE */
+ png_ptr->background_1 = png_ptr->background;
+# endif
+
+ /* This needs to change - in the palette image case a whole set of tables are
+ * built when it would be quicker to just calculate the correct value for
+ * each palette entry directly. Also, the test is too tricky - why check
+ * PNG_RGB_TO_GRAY if PNG_GAMMA is not set? The answer seems to be that
+ * PNG_GAMMA is cancelled even if the gamma is known? The test excludes the
+ * PNG_COMPOSE case, so apparently if there is no *overall* gamma correction
+ * the gamma tables will not be built even if composition is required on a
+ * gamma encoded value.
+ *
+ * In 1.5.4 this is addressed below by an additional check on the individual
+ * file gamma - if it is not 1.0 both RGB_TO_GRAY and COMPOSE need the
+ * tables.
+ */
+ if ((png_ptr->transformations & PNG_GAMMA)
+ || ((png_ptr->transformations & PNG_RGB_TO_GRAY)
+ && (png_gamma_significant(png_ptr->gamma) ||
+ png_gamma_significant(png_ptr->screen_gamma)))
+ || ((png_ptr->transformations & PNG_COMPOSE)
+ && (png_gamma_significant(png_ptr->gamma)
+ || png_gamma_significant(png_ptr->screen_gamma)
+# ifdef PNG_READ_BACKGROUND_SUPPORTED
+ || (png_ptr->background_gamma_type == PNG_BACKGROUND_GAMMA_UNIQUE
+ && png_gamma_significant(png_ptr->background_gamma))
+# endif
+ )) || ((png_ptr->transformations & PNG_ENCODE_ALPHA)
+ && png_gamma_significant(png_ptr->screen_gamma))
+ )
+ {
+ png_build_gamma_table(png_ptr, png_ptr->bit_depth);
+
+#ifdef PNG_READ_BACKGROUND_SUPPORTED
+ if (png_ptr->transformations & PNG_COMPOSE)
+ {
+ /* Issue a warning about this combination: because RGB_TO_GRAY is
+ * optimized to do the gamma transform if present yet do_background has
+ * to do the same thing if both options are set a
+ * double-gamma-correction happens. This is true in all versions of
+ * libpng to date.
+ */
+ if (png_ptr->transformations & PNG_RGB_TO_GRAY)
+ png_warning(png_ptr,
+ "libpng does not support gamma+background+rgb_to_gray");
+
+ if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
+ {
+ /* We don't get to here unless there is a tRNS chunk with non-opaque
+ * entries - see the checking code at the start of this function.
+ */
+ png_color back, back_1;
projects / wxWidgets.git / blobdiff