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tiny thumbnail speedup

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thumbnail can skip premultiply/unpre if there's no residual resize
This commit is contained in:
John Cupitt 2020-09-21 09:38:11 +01:00
parent 0c7b65e156
commit 10bada0161
1 changed files with 20 additions and 18 deletions
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38
libvips/resample/thumbnail.c
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@ -736,24 +736,6 @@ vips_thumbnail_build( VipsObject *object )
return( -1 );
in = t[2];
/* If there's an alpha, we have to premultiply before shrinking. See
* https://github.com/libvips/libvips/issues/291
*/
have_premultiplied = FALSE;
if( vips_image_hasalpha( in ) ) {
g_info( "premultiplying alpha" );
if( vips_premultiply( in, &t[3], NULL ) )
return( -1 );
have_premultiplied = TRUE;
/* vips_premultiply() makes a float image. When we
* vips_unpremultiply() below, we need to cast back to the
* pre-premultiply format.
*/
unpremultiplied_format = in->BandFmt;
in = t[3];
}
/* Shrink to preshrunk_page_height, so we work for multi-page images.
*/
vips_thumbnail_calculate_shrink( thumbnail,
@ -771,6 +753,26 @@ vips_thumbnail_build( VipsObject *object )
vshrink = (double) in->Ysize / target_image_height;
}
/* If there's an alpha, we have to premultiply before shrinking. See
* https://github.com/libvips/libvips/issues/291
*/
have_premultiplied = FALSE;
if( vips_image_hasalpha( in ) &&
hshrink != 1.0 &&
vshrink != 1.0 ) {
g_info( "premultiplying alpha" );
if( vips_premultiply( in, &t[3], NULL ) )
return( -1 );
have_premultiplied = TRUE;
/* vips_premultiply() makes a float image. When we
* vips_unpremultiply() below, we need to cast back to the
* pre-premultiply format.
*/
unpremultiplied_format = in->BandFmt;
in = t[3];
}
if( vips_resize( in, &t[4], 1.0 / hshrink,
"vscale", 1.0 / vshrink,
NULL ) )