[This is preliminary documentation and subject to change.]
The BLENDFUNCTION structure controls blending by specifying the blending functions for source and destination bitmaps.
typedef struct _BLENDFUNCTION
{
BYTE BlendOp;
BYTE BlendFlags;
BYTE SourceConstantAlpha;
BYTE AlphaFormat;
}BLENDFUNCTION, *PBLENDFUNCTION, *LPBLENDFUNCTION;
Value | Meaning |
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AC_SRC_ALPHA | This flag is set when the bitmap has an Alpha channel. |
When the AC_SRC_OVER operation is used, the source bitmap is placed over the destination bitmap based on the alpha values of the source pixels.
If the source bitmap has no per-pixel alpha value, the blend is based on a constant source alpha value as shown in the following table.
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If the source bitmap has per-pixel alpha, the constant alpha is not used (0xff) as shown in the following table.
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If the destination bitmap has an alpha channel, then:
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If the source has pixel per alpha, the constant alpha is not 0xff.
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Windows NT: Requires version 5.0 or later.
Windows: Requires Windows 98 or later.
Windows CE: Unsupported.
Header: Declared in wingdi.h.
Bitmaps Overview, Bitmap Structures