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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 // use the Abstract Pixel API to be able to set RGB and A bytes directly into
// the wxBitmap's pixel buffer. // 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 _BitmapFromBufferAlpha;
%newobject _BitmapFromBuffer; %newobject _BitmapFromBuffer;
%inline %{ %inline %{
@@ -348,10 +360,11 @@ the ``type`` parameter.", "");
for (int y=0; y<height; y++) { for (int y=0; y<height; y++) {
wxAlphaPixelData::Iterator rowStart = p; wxAlphaPixelData::Iterator rowStart = p;
for (int x=0; x<width; x++) { for (int x=0; x<width; x++) {
p.Red() = *(data++); byte a = *(alpha++);
p.Green() = *(data++); p.Red() = wxPy_premultiply(*(data++), a);
p.Blue() = *(data++); p.Green() = wxPy_premultiply(*(data++), a);
p.Alpha() = *(alpha++); p.Blue() = wxPy_premultiply(*(data++), a);
p.Alpha() = a;
++p; ++p;
} }
p = rowStart; 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 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 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 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 Unlike `wx.ImageFromBuffer` the bitmap created with this function does not
share the memory buffer with the buffer object. This is because the 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++) { for (int y=0; y<height; y++) {
wxAlphaPixelData::Iterator rowStart = p; wxAlphaPixelData::Iterator rowStart = p;
for (int x=0; x<width; x++) { for (int x=0; x<width; x++) {
p.Red() = *(data++); byte a = data[3];
p.Green() = *(data++); p.Red() = wxPy_premultiply(*(data++), a);
p.Blue() = *(data++); p.Green() = wxPy_premultiply(*(data++), a);
p.Alpha() = *(data++); p.Blue() = wxPy_premultiply(*(data++), a);
p.Alpha() = a; data++;
++p; ++p;
} }
p = rowStart; p = rowStart;
@@ -469,7 +485,9 @@ def BitmapFromBufferRGBA(width, height, dataBuffer):
parameter must be a Python object that implements the buffer interface, or 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 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, 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 Unlike `wx.ImageFromBuffer` the bitmap created with this function does not
share the memory buffer with the buffer object. This is because the share the memory buffer with the buffer object. This is because the