#if 0 /* in case someone actually tries to compile this */
/* example.c - an example of using libpng
- * Last changed in libpng 1.2.33 [December 18, 2008]
+ * Last changed in libpng 1.4.2 [May 6, 2010]
* This file has been placed in the public domain by the authors.
- * Maintained 1998-2008 Glenn Randers-Pehrson
+ * Maintained 1998-2010 Glenn Randers-Pehrson
* Maintained 1996, 1997 Andreas Dilger)
* Written 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
*/
if ((fp = fopen(file_name, "rb")) == NULL)
return (ERROR);
+
#else no_open_file /* prototype 2 */
-void read_png(FILE *fp, unsigned int sig_read) /* file is already open */
+void read_png(FILE *fp, unsigned int sig_read) /* File is already open */
{
png_structp png_ptr;
png_infop info_ptr;
png_uint_32 width, height;
int bit_depth, color_type, interlace_type;
-#endif no_open_file /* only use one prototype! */
+#endif no_open_file /* Only use one prototype! */
/* Create and initialize the png_struct with the desired error handler
* functions. If you want to use the default stderr and longjump method,
if (info_ptr == NULL)
{
fclose(fp);
- png_destroy_read_struct(&png_ptr, png_infopp_NULL, png_infopp_NULL);
+ png_destroy_read_struct(&png_ptr, NULL, NULL);
return (ERROR);
}
if (setjmp(png_jmpbuf(png_ptr)))
{
/* Free all of the memory associated with the png_ptr and info_ptr */
- png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
+ png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
fclose(fp);
/* If we get here, we had a problem reading the file */
return (ERROR);
* If you have enough memory to read in the entire image at once,
* and you need to specify only transforms that can be controlled
* with one of the PNG_TRANSFORM_* bits (this presently excludes
- * dithering, filling, setting background, and doing gamma
+ * quantizing, filling, setting background, and doing gamma
* adjustment), then you can read the entire image (including
* pixels) into the info structure with this call:
*/
- png_read_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
+ png_read_png(png_ptr, info_ptr, png_transforms, NULL);
+
#else
/* OK, you're doing it the hard way, with the lower-level functions */
png_read_info(png_ptr, info_ptr);
png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
- &interlace_type, int_p_NULL, int_p_NULL);
+ &interlace_type, NULL, NULL);
-/* Set up the data transformations you want. Note that these are all
- * optional. Only call them if you want/need them. Many of the
- * transformations only work on specific types of images, and many
- * are mutually exclusive.
- */
+ /* Set up the data transformations you want. Note that these are all
+ * optional. Only call them if you want/need them. Many of the
+ * transformations only work on specific types of images, and many
+ * are mutually exclusive.
+ */
- /* tell libpng to strip 16 bit/color files down to 8 bits/color */
+ /* Tell libpng to strip 16 bit/color files down to 8 bits/color */
png_set_strip_16(png_ptr);
/* Strip alpha bytes from the input data without combining with the
png_set_background(png_ptr, &my_background,
PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
- /* Some suggestions as to how to get a screen gamma value */
-
- /* Note that screen gamma is the display_exponent, which includes
- * the CRT_exponent and any correction for viewing conditions */
+ /* Some suggestions as to how to get a screen gamma value
+ *
+ * Note that screen gamma is the display_exponent, which includes
+ * the CRT_exponent and any correction for viewing conditions
+ */
if (/* We have a user-defined screen gamma value */)
{
screen_gamma = user-defined screen_gamma;
/* If we don't have another value */
else
{
- screen_gamma = 2.2; /* A good guess for a PC monitors in a dimly
+ screen_gamma = 2.2; /* A good guess for a PC monitor in a dimly
lit room */
screen_gamma = 1.7 or 1.0; /* A good guess for Mac systems */
}
png_set_gamma(png_ptr, screen_gamma, 0.45455);
}
- /* Dither RGB files down to 8 bit palette or reduce palettes
+#ifdef PNG_READ_QUANTIZE_SUPPORTED
+ /* Quantize RGB files down to 8 bit palette or reduce palettes
* to the number of colors available on your screen.
*/
if (color_type & PNG_COLOR_MASK_COLOR)
png_colorp palette;
/* This reduces the image to the application supplied palette */
- if (/* we have our own palette */)
+ if (/* We have our own palette */)
{
- /* An array of colors to which the image should be dithered */
+ /* An array of colors to which the image should be quantized */
png_color std_color_cube[MAX_SCREEN_COLORS];
- png_set_dither(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
- MAX_SCREEN_COLORS, png_uint_16p_NULL, 0);
+ /* Prior to libpng-1.4.2, this was png_set_dither(). */
+ png_set_quantize(png_ptr, std_color_cube, MAX_SCREEN_COLORS,
+ MAX_SCREEN_COLORS, NULL, 0);
}
/* This reduces the image to the palette supplied in the file */
else if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette))
png_get_hIST(png_ptr, info_ptr, &histogram);
- png_set_dither(png_ptr, palette, num_palette,
+ png_set_quantize(png_ptr, palette, num_palette,
max_screen_colors, histogram, 0);
}
}
+#endif /* PNG_READ_QUANTIZE_SUPPORTED */
- /* invert monochrome files to have 0 as white and 1 as black */
+ /* Invert monochrome files to have 0 as white and 1 as black */
png_set_invert_mono(png_ptr);
/* If you want to shift the pixel values from the range [0,255] or
*/
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT))
{
- png_color_8p sig_bit;
+ png_color_8p sig_bit_p;
- png_get_sBIT(png_ptr, info_ptr, &sig_bit);
- png_set_shift(png_ptr, sig_bit);
+ png_get_sBIT(png_ptr, info_ptr, &sig_bit_p);
+ png_set_shift(png_ptr, sig_bit_p);
}
- /* flip the RGB pixels to BGR (or RGBA to BGRA) */
+ /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
if (color_type & PNG_COLOR_MASK_COLOR)
png_set_bgr(png_ptr);
- /* swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
+ /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
png_set_swap_alpha(png_ptr);
- /* swap bytes of 16 bit files to least significant byte first */
+ /* Swap bytes of 16 bit files to least significant byte first */
png_set_swap(png_ptr);
/* Add filler (or alpha) byte (before/after each RGB triplet) */
/* The easiest way to read the image: */
png_bytep row_pointers[height];
+ /* Clear the pointer array */
+ for (row = 0; row < height; row++)
+ row_pointers[row] = NULL;
+
for (row = 0; row < height; row++)
- {
row_pointers[row] = png_malloc(png_ptr, png_get_rowbytes(png_ptr,
info_ptr));
- }
/* Now it's time to read the image. One of these methods is REQUIRED */
#ifdef entire /* Read the entire image in one go */
#ifdef single /* Read the image a single row at a time */
for (y = 0; y < height; y++)
{
- png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL, 1);
+ png_read_rows(png_ptr, &row_pointers[y], NULL, 1);
}
#else no_single /* Read the image several rows at a time */
for (y = 0; y < height; y += number_of_rows)
{
#ifdef sparkle /* Read the image using the "sparkle" effect. */
- png_read_rows(png_ptr, &row_pointers[y], png_bytepp_NULL,
+ png_read_rows(png_ptr, &row_pointers[y], NULL,
number_of_rows);
#else no_sparkle /* Read the image using the "rectangle" effect */
- png_read_rows(png_ptr, png_bytepp_NULL, &row_pointers[y],
+ png_read_rows(png_ptr, NULL, &row_pointers[y],
number_of_rows);
-#endif no_sparkle /* use only one of these two methods */
+#endif no_sparkle /* Use only one of these two methods */
}
- /* if you want to display the image after every pass, do
- so here */
-#endif no_single /* use only one of these two methods */
+ /* If you want to display the image after every pass, do so here */
+#endif no_single /* Use only one of these two methods */
}
-#endif no_entire /* use only one of these two methods */
+#endif no_entire /* Use only one of these two methods */
- /* read rest of file, and get additional chunks in info_ptr - REQUIRED */
+ /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
png_read_end(png_ptr, info_ptr);
#endif hilevel
/* At this point you have read the entire image */
- /* clean up after the read, and free any memory allocated - REQUIRED */
- png_destroy_read_struct(&png_ptr, &info_ptr, png_infopp_NULL);
+ /* Clean up after the read, and free any memory allocated - REQUIRED */
+ png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
- /* close the file */
+ /* Close the file */
fclose(fp);
- /* that's it */
+ /* That's it */
return (OK);
}
-/* progressively read a file */
+/* Progressively read a file */
int
initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
if (*info_ptr == NULL)
{
- png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
+ png_destroy_read_struct(png_ptr, info_ptr, NULL);
return (ERROR);
}
if (setjmp(png_jmpbuf((*png_ptr))))
{
- png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
+ png_destroy_read_struct(png_ptr, info_ptr, NULL);
return (ERROR);
}
if (setjmp(png_jmpbuf((*png_ptr))))
{
/* Free the png_ptr and info_ptr memory on error */
- png_destroy_read_struct(png_ptr, info_ptr, png_infopp_NULL);
+ png_destroy_read_struct(png_ptr, info_ptr, NULL);
return (ERROR);
}
/* This one's new also. Simply give it chunks of data as
* they arrive from the data stream (in order, of course).
- * On Segmented machines, don't give it any more than 64K.
+ * On segmented machines, don't give it any more than 64K.
* The library seems to run fine with sizes of 4K, although
* you can give it much less if necessary (I assume you can
* give it chunks of 1 byte, but I haven't tried with less
info_callback(png_structp png_ptr, png_infop info)
{
-/* do any setup here, including setting any of the transformations
- * mentioned in the Reading PNG files section. For now, you _must_
- * call either png_start_read_image() or png_read_update_info()
- * after all the transformations are set (even if you don't set
- * any). You may start getting rows before png_process_data()
- * returns, so this is your last chance to prepare for that.
- */
+ /* Do any setup here, including setting any of the transformations
+ * mentioned in the Reading PNG files section. For now, you _must_
+ * call either png_start_read_image() or png_read_update_info()
+ * after all the transformations are set (even if you don't set
+ * any). You may start getting rows before png_process_data()
+ * returns, so this is your last chance to prepare for that.
+ */
}
row_callback(png_structp png_ptr, png_bytep new_row,
png_uint_32 row_num, int pass)
{
-/*
- * This function is called for every row in the image. If the
- * image is interlaced, and you turned on the interlace handler,
- * this function will be called for every row in every pass.
- *
- * In this function you will receive a pointer to new row data from
- * libpng called new_row that is to replace a corresponding row (of
- * the same data format) in a buffer allocated by your application.
- *
- * The new row data pointer new_row may be NULL, indicating there is
- * no new data to be replaced (in cases of interlace loading).
- *
- * If new_row is not NULL then you need to call
- * png_progressive_combine_row() to replace the corresponding row as
- * shown below:
- */
- /* Check if row_num is in bounds. */
- if ((row_num >= 0) && (row_num < height))
- {
- /* Get pointer to corresponding row in our
- * PNG read buffer.
- */
- png_bytep old_row = ((png_bytep *)our_data)[row_num];
-
- /* If both rows are allocated then copy the new row
- * data to the corresponding row data.
- */
- if ((old_row != NULL) && (new_row != NULL))
- png_progressive_combine_row(png_ptr, old_row, new_row);
- }
-/*
- * The rows and passes are called in order, so you don't really
- * need the row_num and pass, but I'm supplying them because it
- * may make your life easier.
- *
- * For the non-NULL rows of interlaced images, you must call
- * png_progressive_combine_row() passing in the new row and the
- * old row, as demonstrated above. You can call this function for
- * NULL rows (it will just return) and for non-interlaced images
- * (it just does the png_memcpy for you) if it will make the code
- * easier. Thus, you can just do this for all cases:
- */
+ /*
+ * This function is called for every row in the image. If the
+ * image is interlaced, and you turned on the interlace handler,
+ * this function will be called for every row in every pass.
+ *
+ * In this function you will receive a pointer to new row data from
+ * libpng called new_row that is to replace a corresponding row (of
+ * the same data format) in a buffer allocated by your application.
+ *
+ * The new row data pointer "new_row" may be NULL, indicating there is
+ * no new data to be replaced (in cases of interlace loading).
+ *
+ * If new_row is not NULL then you need to call
+ * png_progressive_combine_row() to replace the corresponding row as
+ * shown below:
+ */
+
+ /* Get pointer to corresponding row in our
+ * PNG read buffer.
+ */
+ png_bytep old_row = ((png_bytep *)our_data)[row_num];
+ /* If both rows are allocated then copy the new row
+ * data to the corresponding row data.
+ */
+ if ((old_row != NULL) && (new_row != NULL))
png_progressive_combine_row(png_ptr, old_row, new_row);
-/* where old_row is what was displayed for previous rows. Note
- * that the first pass (pass == 0 really) will completely cover
- * the old row, so the rows do not have to be initialized. After
- * the first pass (and only for interlaced images), you will have
- * to pass the current row as new_row, and the function will combine
- * the old row and the new row.
- */
+ /*
+ * The rows and passes are called in order, so you don't really
+ * need the row_num and pass, but I'm supplying them because it
+ * may make your life easier.
+ *
+ * For the non-NULL rows of interlaced images, you must call
+ * png_progressive_combine_row() passing in the new row and the
+ * old row, as demonstrated above. You can call this function for
+ * NULL rows (it will just return) and for non-interlaced images
+ * (it just does the png_memcpy for you) if it will make the code
+ * easier. Thus, you can just do this for all cases:
+ */
+
+ png_progressive_combine_row(png_ptr, old_row, new_row);
+
+ /* where old_row is what was displayed for previous rows. Note
+ * that the first pass (pass == 0 really) will completely cover
+ * the old row, so the rows do not have to be initialized. After
+ * the first pass (and only for interlaced images), you will have
+ * to pass the current row as new_row, and the function will combine
+ * the old row and the new row.
+ */
}
end_callback(png_structp png_ptr, png_infop info)
{
-/* this function is called when the whole image has been read,
- * including any chunks after the image (up to and including
- * the IEND). You will usually have the same info chunk as you
- * had in the header, although some data may have been added
- * to the comments and time fields.
- *
- * Most people won't do much here, perhaps setting a flag that
- * marks the image as finished.
- */
+ /* This function is called when the whole image has been read,
+ * including any chunks after the image (up to and including
+ * the IEND). You will usually have the same info chunk as you
+ * had in the header, although some data may have been added
+ * to the comments and time fields.
+ *
+ * Most people won't do much here, perhaps setting a flag that
+ * marks the image as finished.
+ */
}
-/* write a png file */
+/* Write a png file */
void write_png(char *file_name /* , ... other image information ... */)
{
FILE *fp;
png_infop info_ptr;
png_colorp palette;
- /* open the file */
+ /* Open the file */
fp = fopen(file_name, "wb");
if (fp == NULL)
return (ERROR);
if (info_ptr == NULL)
{
fclose(fp);
- png_destroy_write_struct(&png_ptr, png_infopp_NULL);
+ png_destroy_write_struct(&png_ptr, NULL);
return (ERROR);
}
*/
if (setjmp(png_jmpbuf(png_ptr)))
{
- /* If we get here, we had a problem reading the file */
+ /* If we get here, we had a problem writing the file */
fclose(fp);
png_destroy_write_struct(&png_ptr, &info_ptr);
return (ERROR);
}
/* One of the following I/O initialization functions is REQUIRED */
+
#ifdef streams /* I/O initialization method 1 */
- /* set up the output control if you are using standard C streams */
+ /* Set up the output control if you are using standard C streams */
png_init_io(png_ptr, fp);
+
#else no_streams /* I/O initialization method 2 */
/* If you are using replacement write functions, instead of calling
- * png_init_io() here you would call */
+ * png_init_io() here you would call
+ */
png_set_write_fn(png_ptr, (void *)user_io_ptr, user_write_fn,
user_IO_flush_function);
/* where user_io_ptr is a structure you want available to the callbacks */
-#endif no_streams /* only use one initialization method */
+#endif no_streams /* Only use one initialization method */
#ifdef hilevel
/* This is the easy way. Use it if you already have all the
- * image info living info in the structure. You could "|" many
+ * image info living in the structure. You could "|" many
* PNG_TRANSFORM flags into the png_transforms integer here.
*/
- png_write_png(png_ptr, info_ptr, png_transforms, png_voidp_NULL);
+ png_write_png(png_ptr, info_ptr, png_transforms, NULL);
+
#else
/* This is the hard way */
png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, PNG_COLOR_TYPE_???,
PNG_INTERLACE_????, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
- /* set the palette if there is one. REQUIRED for indexed-color images */
+ /* Set the palette if there is one. REQUIRED for indexed-color images */
palette = (png_colorp)png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH
* png_sizeof(png_color));
- /* ... set palette colors ... */
+ /* ... Set palette colors ... */
png_set_PLTE(png_ptr, info_ptr, palette, PNG_MAX_PALETTE_LENGTH);
/* You must not free palette here, because png_set_PLTE only makes a link to
- the palette that you malloced. Wait until you are about to destroy
- the png structure. */
+ * the palette that you malloced. Wait until you are about to destroy
+ * the png structure.
+ */
- /* optional significant bit chunk */
- /* if we are dealing with a grayscale image then */
+ /* Optional significant bit (sBIT) chunk */
+ png_color_8 sig_bit;
+ /* If we are dealing with a grayscale image then */
sig_bit.gray = true_bit_depth;
- /* otherwise, if we are dealing with a color image then */
+ /* Otherwise, if we are dealing with a color image then */
sig_bit.red = true_red_bit_depth;
sig_bit.green = true_green_bit_depth;
sig_bit.blue = true_blue_bit_depth;
- /* if the image has an alpha channel then */
+ /* If the image has an alpha channel then */
sig_bit.alpha = true_alpha_bit_depth;
- png_set_sBIT(png_ptr, info_ptr, sig_bit);
+ png_set_sBIT(png_ptr, info_ptr, &sig_bit);
/* Optional gamma chunk is strongly suggested if you have any guess
text_ptr[2].compression = PNG_TEXT_COMPRESSION_zTXt;
#ifdef PNG_iTXt_SUPPORTED
text_ptr[0].lang = NULL;
+ text_ptr[0].lang_key = NULL;
text_ptr[1].lang = NULL;
+ text_ptr[1].lang_key = NULL;
text_ptr[2].lang = NULL;
+ text_ptr[2].lang_key = NULL;
#endif
png_set_text(png_ptr, info_ptr, text_ptr, 3);
- /* other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs, */
- /* note that if sRGB is present the gAMA and cHRM chunks must be ignored
- * on read and must be written in accordance with the sRGB profile */
+ /* Other optional chunks like cHRM, bKGD, tRNS, tIME, oFFs, pHYs */
+
+ /* Note that if sRGB is present the gAMA and cHRM chunks must be ignored
+ * on read and, if your application chooses to write them, they must
+ * be written in accordance with the sRGB profile
+ */
/* Write the file header information. REQUIRED */
png_write_info(png_ptr, info_ptr);
* write_my_chunk();
* png_write_info(png_ptr, info_ptr);
*
- * However, given the level of known- and unknown-chunk support in 1.1.0
+ * However, given the level of known- and unknown-chunk support in 1.2.0
* and up, this should no longer be necessary.
*/
* at the end.
*/
- /* set up the transformations you want. Note that these are
+ /* Set up the transformations you want. Note that these are
* all optional. Only call them if you want them.
*/
- /* invert monochrome pixels */
+ /* Invert monochrome pixels */
png_set_invert_mono(png_ptr);
/* Shift the pixels up to a legal bit depth and fill in
*/
png_set_shift(png_ptr, &sig_bit);
- /* pack pixels into bytes */
+ /* Pack pixels into bytes */
png_set_packing(png_ptr);
- /* swap location of alpha bytes from ARGB to RGBA */
+ /* Swap location of alpha bytes from ARGB to RGBA */
png_set_swap_alpha(png_ptr);
/* Get rid of filler (OR ALPHA) bytes, pack XRGB/RGBX/ARGB/RGBA into
*/
png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
- /* flip BGR pixels to RGB */
+ /* Flip BGR pixels to RGB */
png_set_bgr(png_ptr);
- /* swap bytes of 16-bit files to most significant byte first */
+ /* Swap bytes of 16-bit files to most significant byte first */
png_set_swap(png_ptr);
- /* swap bits of 1, 2, 4 bit packed pixel formats */
+ /* Swap bits of 1, 2, 4 bit packed pixel formats */
png_set_packswap(png_ptr);
- /* turn on interlace handling if you are not using png_write_image() */
+ /* Turn on interlace handling if you are not using png_write_image() */
if (interlacing)
number_passes = png_set_interlace_handling(png_ptr);
else
row_pointers[k] = image + k*width*bytes_per_pixel;
/* One of the following output methods is REQUIRED */
-#ifdef entire /* write out the entire image data in one call */
+
+#ifdef entire /* Write out the entire image data in one call */
png_write_image(png_ptr, row_pointers);
- /* the other way to write the image - deal with interlacing */
+ /* The other way to write the image - deal with interlacing */
+
+#else no_entire /* Write out the image data by one or more scanlines */
-#else no_entire /* write out the image data by one or more scanlines */
/* The number of passes is either 1 for non-interlaced images,
* or 7 for interlaced images.
*/
/* If you are only writing one row at a time, this works */
for (y = 0; y < height; y++)
- {
png_write_rows(png_ptr, &row_pointers[y], 1);
- }
}
-#endif no_entire /* use only one output method */
+#endif no_entire /* Use only one output method */
/* You can write optional chunks like tEXt, zTXt, and tIME at the end
- * as well. Shouldn't be necessary in 1.1.0 and up as all the public
+ * as well. Shouldn't be necessary in 1.2.0 and up as all the public
* chunks are supported and you can use png_set_unknown_chunks() to
* register unknown chunks into the info structure to be written out.
*/
#endif hilevel
/* If you png_malloced a palette, free it here (don't free info_ptr->palette,
- as recommended in versions 1.0.5m and earlier of this example; if
- libpng mallocs info_ptr->palette, libpng will free it). If you
- allocated it with malloc() instead of png_malloc(), use free() instead
- of png_free(). */
+ * as recommended in versions 1.0.5m and earlier of this example; if
+ * libpng mallocs info_ptr->palette, libpng will free it). If you
+ * allocated it with malloc() instead of png_malloc(), use free() instead
+ * of png_free().
+ */
png_free(png_ptr, palette);
palette = NULL;
/* Similarly, if you png_malloced any data that you passed in with
- png_set_something(), such as a hist or trans array, free it here,
- when you can be sure that libpng is through with it. */
+ * png_set_something(), such as a hist or trans array, free it here,
+ * when you can be sure that libpng is through with it.
+ */
png_free(png_ptr, trans);
trans = NULL;
+ /* Whenever you use png_free() it is a good idea to set the pointer to
+ * NULL in case your application inadvertently tries to png_free() it
+ * again. When png_free() sees a NULL it returns without action, thus
+ * avoiding the double-free security problem.
+ */
- /* clean up after the write, and free any memory allocated */
+ /* Clean up after the write, and free any memory allocated */
png_destroy_write_struct(&png_ptr, &info_ptr);
- /* close the file */
+ /* Close the file */
fclose(fp);
- /* that's it */
+ /* That's it */
return (OK);
}
projects / wxWidgets.git / blobdiff