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Merge pull request #228 from bgilbert/unpremultiply-performance 

Improve performance of openslide2vips argb2rgba()
This commit is contained in:
John Cupitt 2015-01-27 09:53:52 +00:00
parent 6676b9a24f 6444a52582
commit 4012341d59
1 changed files with 14 additions and 10 deletions
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24
libvips/foreign/openslide2vips.c
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@ -2,7 +2,7 @@
*
* Benjamin Gilbert
*
* Copyright (c) 2011-2014 Carnegie Mellon University
* Copyright (c) 2011-2015 Carnegie Mellon University
*
* 26/11/11
* - initial version
@ -45,6 +45,8 @@
* - add autocrop toggle
* 9/8/14
* - do argb -> rgba for associated as well
* 27/1/15
* - unpremultiplication speedups for fully opaque/transparent pixels
*/
/*
@ -414,20 +416,22 @@ argb2rgba( uint32_t *buf, int n, uint32_t bg )
uint8_t a = x >> 24;
VipsPel *out = (VipsPel *) p;
if( a != 0 ) {
if( a == 255 ) {
*p = GUINT32_TO_BE((x << 8) | 255);
}
else if( a == 0 ) {
/* Use background color.
*/
*p = GUINT32_TO_BE((bg << 8) | 255);
}
else {
/* Undo premultiplication.
*/
out[0] = 255 * ((x >> 16) & 255) / a;
out[1] = 255 * ((x >> 8) & 255) / a;
out[2] = 255 * (x & 255) / a;
out[3] = 255;
}
else {
/* Use background color.
*/
out[0] = (bg >> 16) & 255;
out[1] = (bg >> 8) & 255;
out[2] = bg & 255;
out[3] = 255;
}
}
}