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moore vips_resize() tuning

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put back the mild post-shrink sharpen, a little more anti-alias

see https://github.com/jcupitt/libvips/issues/404#issuecomment-195297607
This commit is contained in:
John Cupitt 2016-03-11 10:17:41 +00:00
parent 5d31d8e824
commit 08e8c27e38
1 changed files with 18 additions and 1 deletions
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19
libvips/resample/resize.c
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@ -151,7 +151,7 @@ vips_resize_build( VipsObject *object )
* Don't try to be clever for non-rectangular shrinks. We just
* consider the horizontal factor.
*/
sigma = (1.0 / hresidual) / 2.4;
sigma = (1.0 / hresidual) / 2.3;
anti_alias = hresidual < 0.9 && sigma > 0.45;
if( anti_alias ) {
vips_info( class->nickname, "anti-alias sigma %g", sigma );
@ -183,6 +183,23 @@ vips_resize_build( VipsObject *object )
in = t[3];
}
/* If we are upsampling, don't sharpen. Also don't sharpen if we
* skipped the anti-alias filter.
*/
if( int_hshrink >= 1 &&
anti_alias ) {
vips_info( class->nickname, "final sharpen" );
t[4] = vips_image_new_matrixv( 3, 3,
-1.0, -1.0, -1.0,
-1.0, 32.0, -1.0,
-1.0, -1.0, -1.0 );
vips_image_set_double( t[4], "scale", 24 );
if( vips_conv( in, &t[5], t[4], NULL ) )
return( -1 );
in = t[5];
}
if( vips_image_write( in, resample->out ) )
return( -1 );