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better Q computation

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stolen from cjxl.cc
This commit is contained in:
John Cupitt 2021-04-14 17:34:30 +01:00
parent c48a82d937
commit 2a51cf23a3
1 changed files with 7 additions and 4 deletions
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11
libvips/foreign/jxlsave.c
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@ -215,11 +215,13 @@ vips_foreign_save_jxl_build( VipsObject *object )
return( -1 );
/* If Q is set and distance is not, use Q to set a rough distance
* value. Q 75 is distance 1.0, Q 100 is distance 0.0.
* value. Formula stolen from cjxl.c and very roughly approximates
* libjpeg values.
*/
if( vips_object_argument_isset( object, "Q" ) &&
!vips_object_argument_isset( object, "distance" ) )
jxl->distance = (100 - jxl->Q) / 25.0;
if( !vips_object_argument_isset( object, "distance" ) )
jxl->distance = jxl->Q >= 30 ?
0.1 + (100 - jxl->Q) * 0.09 :
6.4 + pow(2.5, (30 - jxl->Q) / 5.0f) / 6.25f;
jxl->runner = JxlThreadParallelRunnerCreate( NULL,
vips_concurrency_get() );
@ -475,6 +477,7 @@ vips_foreign_save_jxl_init( VipsForeignSaveJxl *jxl )
jxl->distance = 1.0;
jxl->effort = 7;
jxl->lossless = FALSE;
jxl->Q = 75;
}
typedef struct _VipsForeignSaveJxlFile {