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better error detection in spngload

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Do a speculative spng_get_trns() in header read to force all chunks to
be parsed.

Thanks randy408

See https://github.com/randy408/libspng/issues/145#issuecomment-744495084
This commit is contained in:
John Cupitt 2021-01-05 03:54:48 +00:00
parent 7a33be716b
commit e1a9397c15
2 changed files with 15 additions and 0 deletions
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1
ChangeLog
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@ -3,6 +3,7 @@
- check for null memory sources [kleisauke]
- revise ppmload, fixing a couple of small bugs
- signal error on EOF in jpegload more reliably [bozaro]
- better error detection in spngload [randy408]
18/12/20 started 8.10.5
- fix potential /0 in animated webp load [lovell]

14
libvips/foreign/spngload.c
View File

@ -373,11 +373,25 @@ vips_foreign_load_png_header( VipsForeignLoad *load )
png->ihdr.bit_depth < 8 )
png->fmt = SPNG_FMT_G8;
/* Try reading the optional transparency chunk. This will cause all
* chunks up to the first IDAT to be read in, so it can fail if any
* chunk has an error.
*/
error = spng_get_trns( png->ctx, &trns );
if( error &&
error != SPNG_ECHUNKAVAIL ) {
vips_error( class->nickname, "%s", spng_strerror( error ) );
return( -1 );
}
/* Expand transparency.
*
* The _ALPHA types should not have the optional trns chunk (they
* always have a transparent band), see
* https://www.w3.org/TR/2003/REC-PNG-20031110/#11tRNS
*
* It's quick and safe to call spng_get_trns() again, and we now know
* it will only fail for no transparency chunk.
*/
if( png->ihdr.color_type == SPNG_COLOR_TYPE_GRAYSCALE_ALPHA ||
png->ihdr.color_type == SPNG_COLOR_TYPE_TRUECOLOR_ALPHA )