- pix-blend-colorprocedure
- in - PPIXD - #f or PPIX1 (see NOTE above)
- in - PPIX1 - “blendee”
- in - PPIX2 - “blender”, usually smaller area than PPIX1
- in - X, Y - origin of PPIX2 relative to origin of PPIX1 (pixels)
- in - FRACT - blending fraction
- in - TRANSPARENT - 1: use transparency, 0: don’t use transparency.
- in - TRANSPIX - color in PPIX2 to be made transparent, typically 0 or 0xffffff00
- returns: blended ppix or #f on error.