$tagBLENDFUNCTION structure controls blending by specifying the blending functions for source and destination bitmaps
Global Const $tagBLENDFUNCTION = "byte Op;byte Flags;byte Alpha;byte Format"
| Op | Specifies the source blend operation: |
| Flags | Must be zero |
| Alpha | Specifies an alpha transparency value to be used on the entire source bitmap. This value is combined with any per-pixel alpha values in the source bitmap. If set to 0, it is assumed that your image is transparent. Set to 255 (opaque) when you only want to use per-pixel alpha values. |
| Format | This member controls the way the source and destination bitmaps are interpreted: AC_SRC_ALPHA - This flag is set when the bitmap has an Alpha channel (that is, per-pixel alpha). Note that the APIs use premultiplied alpha, which means that the red, green and blue channel values in the bitmap must be premultiplied with the alpha channel value. |
The source bitmap used with $tagBLENDFUNCTION must be 32 bpp