Image::histogram_luma() -> FixedArray[Int] (256 bins) and Image::histogram_rgb() -> per-channel 256-bin arrays. Tests: bin sums equal pixel count, flat image concentrates in one bin, hand-counted tiny image.
Image::histogram_luma() -> FixedArray[Int] (256 bins) and Image::histogram_rgb() -> per-channel 256-bin arrays. Tests: bin sums equal pixel count, flat image concentrates in one bin, hand-counted tiny image.