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use premultiplied RGB in raw image demo

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@33616 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2005-04-15 00:14:32 +00:00
parent d391f6679d
commit b068dfe292
1 changed files with 6 additions and 4 deletions
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10
samples/image/image.cpp
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@@ -319,10 +319,12 @@ public:
for ( int x = 0; x < REAL_SIZE; ++x )
{
p.Red() = r;
p.Green() = g;
p.Blue() = b;
p.Alpha() = (Data::Iterator::ChannelType)((x*255.)/REAL_SIZE);
// note that RGB must be premultiplied by alpha
unsigned a = (Data::Iterator::ChannelType)((x*255.)/REAL_SIZE);
p.Red() = r * alpha / 256;
p.Green() = g * alpha / 256;
p.Blue() = b * alpha / 256;
p.Alpha() = a;
++p; // same as p.OffsetX(1)
}