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store bitmap data in premultiplied by alpha format in wxBitmap/wxDIB (patch 991172)

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git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@29622 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Vadim Zeitlin
2004-10-03 14:03:52 +00:00
parent 57c26f8210
commit e5d4ef7410
2 changed files with 33 additions and 49 deletions
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33
src/msw/dib.cpp
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@@ -667,17 +667,30 @@ bool wxDIB::Create(const wxImage& image)
{
// copy one DIB line
unsigned char *dst = dstLineStart;
for ( int x = 0; x < w; x++ )
if ( alpha )
{
// also, the order of RGB is inversed for DIBs
*dst++ = src[2];
*dst++ = src[1];
*dst++ = src[0];
src += 3;
if ( alpha )
*dst++ = *alpha++;
for ( int x = 0; x < w; x++ )
{
// RGB order is reversed, and we need to premultiply
// all channels by alpha value for use with ::AlphaBlend.
const unsigned char a = *alpha++;
*dst++ = (src[2] * a + 127) / 255;
*dst++ = (src[1] * a + 127) / 255;
*dst++ = (src[0] * a + 127) / 255;
*dst++ = a;
src += 3;
}
}
else // no alpha channel
{
for ( int x = 0; x < w; x++ )
{
// RGB order is reversed.
*dst++ = src[2];
*dst++ = src[1];
*dst++ = src[0];
src += 3;
}
}
// pass to the previous line in the image