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Premultiply the alpha on wxMSW in the BitmapFromBuffer* functions so

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the programmers don't have to worry about it.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@40764 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
This commit is contained in:
Robin Dunn 2006-08-23 01:52:20 +00:00
parent 0dcc6f2287
commit 1d1972fce1
1 changed files with 28 additions and 10 deletions
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38
wxPython/src/_bitmap.i
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@ -317,6 +317,18 @@ the ``type`` parameter.", "");
// use the Abstract Pixel API to be able to set RGB and A bytes directly into
// the wxBitmap's pixel buffer.
%{
// See http://tinyurl.com/e5adr for what premultiplying alpha means. It
// appears to me that the other platforms are already doing it, so I'll just
// automatically do it for wxMSW here.
#ifdef __WXMSW__
#define wxPy_premultiply(p, a) ((p) * (a) / 256)
#else
#define wxPy_premultiply(p, a) (p)
#endif
%}
%newobject _BitmapFromBufferAlpha;
%newobject _BitmapFromBuffer;
%inline %{
@ -348,10 +360,11 @@ the ``type`` parameter.", "");
for (int y=0; y<height; y++) {
wxAlphaPixelData::Iterator rowStart = p;
for (int x=0; x<width; x++) {
p.Red() = *(data++);
p.Green() = *(data++);
p.Blue() = *(data++);
p.Alpha() = *(alpha++);
byte a = *(alpha++);
p.Red() = wxPy_premultiply(*(data++), a);
p.Green() = wxPy_premultiply(*(data++), a);
p.Blue() = wxPy_premultiply(*(data++), a);
p.Alpha() = a;
++p;
}
p = rowStart;
@ -402,7 +415,9 @@ def BitmapFromBuffer(width, height, dataBuffer, alphaBuffer=None):
dataBuffer object is expected to contain a series of RGB bytes and be
width*height*3 bytes long. A buffer object can optionally be supplied for
the image's alpha channel data, and it is expected to be width*height
bytes long.
bytes long. On Windows the RGB values are 'premultiplied' by the alpha
values. (The other platforms appear to already be premultiplying the
alpha.)
Unlike `wx.ImageFromBuffer` the bitmap created with this function does not
share the memory buffer with the buffer object. This is because the
@ -449,10 +464,11 @@ def BitmapFromBuffer(width, height, dataBuffer, alphaBuffer=None):
for (int y=0; y<height; y++) {
wxAlphaPixelData::Iterator rowStart = p;
for (int x=0; x<width; x++) {
p.Red() = *(data++);
p.Green() = *(data++);
p.Blue() = *(data++);
p.Alpha() = *(data++);
byte a = data[3];
p.Red() = wxPy_premultiply(*(data++), a);
p.Green() = wxPy_premultiply(*(data++), a);
p.Blue() = wxPy_premultiply(*(data++), a);
p.Alpha() = a; data++;
++p;
}
p = rowStart;
@ -469,7 +485,9 @@ def BitmapFromBufferRGBA(width, height, dataBuffer):
parameter must be a Python object that implements the buffer interface, or
is convertable to a buffer object, such as a string, array, etc. The
dataBuffer object is expected to contain a series of RGBA bytes (red,
gree, blue and alpha) and be width*height*4 bytes long.
green, blue and alpha) and be width*height*4 bytes long. On Windows the
RGB values are 'premultiplied' by the alpha values. (The other platforms
appear to already be premultiplying the alpha.)
Unlike `wx.ImageFromBuffer` the bitmap created with this function does not
share the memory buffer with the buffer object. This is because the