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set interlace flag for interlaced pngs 

if libpng is recent enough
This commit is contained in:
John Cupitt 2019-03-20 21:50:56 +00:00
parent 640994b64a
commit 57ce5a3343
1 changed files with 10 additions and 6 deletions
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14
libvips/foreign/vipspng.c
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@ -533,16 +533,20 @@ png2vips_interlace( Read *read, VipsImage *out )
if( setjmp( png_jmpbuf( read->pPng ) ) ) if( setjmp( png_jmpbuf( read->pPng ) ) )
return( -1 ); return( -1 );
/* Some libpng warn you to call png_set_interlace_handling(); here, but
* that can actually break interlace on older libpngs.
*
* Only set this for libpng 1.6+.
*/
#if PNG_LIBPNG_VER > 10600
(void) png_set_interlace_handling( read->pPng );
#endif
if( !(read->row_pointer = VIPS_ARRAY( NULL, out->Ysize, png_bytep )) ) if( !(read->row_pointer = VIPS_ARRAY( NULL, out->Ysize, png_bytep )) )
return( -1 ); return( -1 );
for( y = 0; y < out->Ysize; y++ ) for( y = 0; y < out->Ysize; y++ )
read->row_pointer[y] = VIPS_IMAGE_ADDR( out, 0, y ); read->row_pointer[y] = VIPS_IMAGE_ADDR( out, 0, y );
/* Some libpng warn you to call png_set_interlace_handling(); here, but
* that can actually break interlace. We have to live with the warning,
* unfortunately.
*/
png_read_image( read->pPng, read->row_pointer ); png_read_image( read->pPng, read->row_pointer );
png_read_end( read->pPng, NULL ); png_read_end( read->pPng, NULL );