- pix-color-fractionprocedure
- in - PPIX - 32bpp
- in - DARKTHR: int32
- Threshold near black. Pixels below aren’t included in stats. Typical: 20
- in - LIGHTTHR: int32
- Threshold near white. Pixels above aren’t included in stats. Typical: 244
- in - DIFFTHR: int32
- Threshold for max diff between R/G/B values. When diff is less, pixel is considered insufficiently colorful. Typical: 60
- in - FACTOR: int32 - Subsampling factor, 1, 2, 4. 1 is no subsampling.
- out - PIXFRAC: ptr to float - optional, use #f to skip.
- Fraction of pixels considered for color content.
- out - COLORFRAC: ptr to float - optional, use #f to skip.
- Fraction of pixels meeting criterion for sufficient color. 0.0 on error.
- returns: 0 if “OK”, 1 on error.