Hello,
as SVG uses premultiplied alpha, we should not multiply it a second time.
hal
>From 47bdab232b382efb89881e79491b7f2c9dbd3ead Mon Sep 17 00:00:00 2001
From: hal <[email protected]>
Date: Sun, 10 Mar 2013 22:56:33 +0100
Subject: [PATCH] Fix: svg uses premultiplied alpha, we didn't respect this.
---
src/iop/watermark.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/src/iop/watermark.c b/src/iop/watermark.c
index 3b8fad7..e30936a 100644
--- a/src/iop/watermark.c
+++ b/src/iop/watermark.c
@@ -645,9 +645,10 @@ void process (struct dt_iop_module_t *self, dt_dev_pixelpipe_iop_t *piece, void
for(int j=0; j<roi_out->height; j++) for(int i=0; i<roi_out->width; i++)
{
float alpha = (sd[3]/255.0)*opacity;
- out[0] = ((1.0-alpha)*in[0]) + (alpha*(sd[2]/255.0));
- out[1] = ((1.0-alpha)*in[1]) + (alpha*(sd[1]/255.0));
- out[2] = ((1.0-alpha)*in[2]) + (alpha*(sd[0]/255.0));
+ /* svg uses a premultiplied alpha, so only use opacity for the blending */
+ out[0] = ((1.0-alpha)*in[0]) + (opacity*(sd[2]/255.0));
+ out[1] = ((1.0-alpha)*in[1]) + (opacity*(sd[1]/255.0));
+ out[2] = ((1.0-alpha)*in[2]) + (opacity*(sd[0]/255.0));
out[3] = in[3];
out+=ch;
--
1.7.10.4
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