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[libpng16] Document how to use a different crc_action while reading chunks

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after IDAT with the sequential reader.
This commit is contained in:
Glenn Randers-Pehrson 2014-02-23 13:43:20 -06:00
parent 079a724833
commit bd792c020f
2 changed files with 26 additions and 10 deletions
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18
libpng-manual.txt
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@ -1216,7 +1216,7 @@ png_set_rgb_to_gray()).
png_get_sRGB(png_ptr, info_ptr, &srgb_intent); png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
file_srgb_intent - the rendering intent (PNG_INFO_sRGB) srgb_intent - the rendering intent (PNG_INFO_sRGB)
The presence of the sRGB chunk The presence of the sRGB chunk
means that the pixel data is in the means that the pixel data is in the
sRGB color space. This chunk also sRGB color space. This chunk also
@ -2166,10 +2166,15 @@ how pngvalid.c does it.
Finishing a sequential read Finishing a sequential read
After you are finished reading the image through the After you are finished reading the image through the
low-level interface, you can finish reading the file. If you are low-level interface, you can finish reading the file.
interested in comments or time, which may be stored either before or
after the image data, you should pass the separate png_info struct if If you want to use a different crc action for handling CRC errors in
you want to keep the comments from before and after the image chunks after the image data, you can call png_set_crc_action()
again at this point.
If you are interested in comments or time, which may be stored either
before or after the image data, you should pass the separate png_info
struct if you want to keep the comments from before and after the image
separate. separate.
png_infop end_info = png_create_info_struct(png_ptr); png_infop end_info = png_create_info_struct(png_ptr);
@ -2185,6 +2190,9 @@ separate.
If you are not interested, you should still call png_read_end() If you are not interested, you should still call png_read_end()
but you can pass NULL, avoiding the need to create an end_info structure. but you can pass NULL, avoiding the need to create an end_info structure.
If you do this, libpng will not process any chunks after IDAT other than
skipping over them and perhaps (depending on whether you have called
png_set_crc_action) checking their CRCs while looking for the IEND chunk.
png_read_end(png_ptr, (png_infop)NULL); png_read_end(png_ptr, (png_infop)NULL);

18
libpng.3
View File

@ -1720,7 +1720,7 @@ png_set_rgb_to_gray()).
png_get_sRGB(png_ptr, info_ptr, &srgb_intent); png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
file_srgb_intent - the rendering intent (PNG_INFO_sRGB) srgb_intent - the rendering intent (PNG_INFO_sRGB)
The presence of the sRGB chunk The presence of the sRGB chunk
means that the pixel data is in the means that the pixel data is in the
sRGB color space. This chunk also sRGB color space. This chunk also
@ -2670,10 +2670,15 @@ how pngvalid.c does it.
.SS Finishing a sequential read .SS Finishing a sequential read
After you are finished reading the image through the After you are finished reading the image through the
low-level interface, you can finish reading the file. If you are low-level interface, you can finish reading the file.
interested in comments or time, which may be stored either before or
after the image data, you should pass the separate png_info struct if If you want to use a different crc action for handling CRC errors in
you want to keep the comments from before and after the image chunks after the image data, you can call png_set_crc_action()
again at this point.
If you are interested in comments or time, which may be stored either
before or after the image data, you should pass the separate png_info
struct if you want to keep the comments from before and after the image
separate. separate.
png_infop end_info = png_create_info_struct(png_ptr); png_infop end_info = png_create_info_struct(png_ptr);
@ -2689,6 +2694,9 @@ separate.
If you are not interested, you should still call png_read_end() If you are not interested, you should still call png_read_end()
but you can pass NULL, avoiding the need to create an end_info structure. but you can pass NULL, avoiding the need to create an end_info structure.
If you do this, libpng will not process any chunks after IDAT other than
skipping over them and perhaps (depending on whether you have called
png_set_crc_action) checking their CRCs while looking for the IEND chunk.
png_read_end(png_ptr, (png_infop)NULL); png_read_end(png_ptr, (png_infop)NULL);