From de3f74f8a6269f6564371fbee93cfec05d61a408 Mon Sep 17 00:00:00 2001
From: kramm <kramm>
Date: Sat, 13 Jan 2007 17:24:41 +0000
Subject: [PATCH] premultiply alpha
---
lib/pdf/GFXOutputDev.cc | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/lib/pdf/GFXOutputDev.cc b/lib/pdf/GFXOutputDev.cc
index 210f88d..81cb642 100644
--- a/lib/pdf/GFXOutputDev.cc
+++ b/lib/pdf/GFXOutputDev.cc
@@ -2717,6 +2717,10 @@ void GFXOutputDev::setSoftMask(GfxState *state, double *bbox, GBool alpha, Funct
states[statepos].softmask = 1;
}
+static inline Guchar div255(int x) {
+ return (Guchar)((x + (x >> 8) + 0x80) >> 8);
+}
+
void GFXOutputDev::clearSoftMask(GfxState *state)
{
if(!states[statepos].softmask)
@@ -2779,14 +2783,12 @@ void GFXOutputDev::clearSoftMask(GfxState *state)
gfxcolor_t* l1 = &maskimg->data[maskimg->width*y];
gfxcolor_t* l2 = &belowimg->data[belowimg->width*y];
for(x=0;x<width;x++) {
- l1->a = 255;
l2->a = (77*l1->r + 151*l1->g + 28*l1->b) >> 8;
- /* premultiply alpha... do we need this? (depends on output device)
- l2->r = (l2->a*l2->r) >> 8;
- l2->g = (l2->a*l2->g) >> 8;
- l2->b = (l2->a*l2->b) >> 8;
- */
+ /* premultiply alpha */
+ l2->r = div255(l2->a*l2->r);
+ l2->g = div255(l2->a*l2->g);
+ l2->b = div255(l2->a*l2->b);
l1++;
l2++;
--
1.7.10.4