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turn off chroma subsample for Q > 90 

see https://github.com/jcupitt/libvips/issues/482
This commit is contained in:
John Cupitt 2016-07-09 18:49:22 +01:00
parent de981cd9ec
commit 4c1e6dd023
2 changed files with 17 additions and 7 deletions
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3
libvips/foreign/jpegsave.c
View File

@ -95,7 +95,8 @@ typedef struct _VipsForeignSaveJpeg {
*/
gboolean trellis_quant;
/* Apply overshooting to samples with extreme values e.g. 0 & 255 for 8-bit.
/* Apply overshooting to samples with extreme values e.g. 0 & 255
* for 8-bit.
*/
gboolean overshoot_deringing;

21
libvips/foreign/vips2jpeg.c
View File

@ -78,6 +78,8 @@
* - add quant_table
* 26/5/16
* - switch to new orientation tag
* 9/7/16
* - turn off chroma subsample for Q > 90
*/
/*
@ -1020,7 +1022,9 @@ write_vips( Write *write, int qfac, const char *profile,
*/
g_assert( in->BandFmt == VIPS_FORMAT_UCHAR );
g_assert( in->Coding == VIPS_CODING_NONE );
g_assert( in->Bands == 1 || in->Bands == 3 || in->Bands == 4 );
g_assert( in->Bands == 1 ||
in->Bands == 3 ||
in->Bands == 4 );
/* Check input image.
*/
@ -1032,7 +1036,8 @@ write_vips( Write *write, int qfac, const char *profile,
write->cinfo.image_width = in->Xsize;
write->cinfo.image_height = in->Ysize;
write->cinfo.input_components = in->Bands;
if( in->Bands == 4 && in->Type == VIPS_INTERPRETATION_CMYK ) {
if( in->Bands == 4 &&
in->Type == VIPS_INTERPRETATION_CMYK ) {
space = JCS_CMYK;
/* IJG always sets an Adobe marker, so we should invert CMYK.
*/
@ -1153,9 +1158,11 @@ write_vips( Write *write, int qfac, const char *profile,
if( progressive )
jpeg_simple_progression( &write->cinfo );
/* Turn off chroma subsampling.
/* Turn off chroma subsampling. Follow IM and do it automatically for
* high Q.
*/
if( no_subsample ) {
if( no_subsample ||
Q > 90 ) {
int i;
for( i = 0; i < in->Bands; i++ ) {
@ -1250,7 +1257,8 @@ vips__jpeg_write_file( VipsImage *in,
*/
if( write_vips( write,
Q, profile, optimize_coding, progressive, strip, no_subsample,
trellis_quant, overshoot_deringing, optimize_scans, quant_table ) ) {
trellis_quant, overshoot_deringing, optimize_scans,
quant_table ) ) {
write_destroy( write );
return( -1 );
}
@ -1535,7 +1543,8 @@ vips__jpeg_write_buffer( VipsImage *in,
*/
if( write_vips( write,
Q, profile, optimize_coding, progressive, strip, no_subsample,
trellis_quant, overshoot_deringing, optimize_scans, quant_table ) ) {
trellis_quant, overshoot_deringing, optimize_scans,
quant_table ) ) {
write_destroy( write );
return( -1 );