Reference: pmDistortRGB
pmDistortRGB(pm) applies a random distortion to the R, G, and B components of each pixel separately, and returns the result. Each R, G, and B component is shifted by at most 10 units of intensity (0..255). pmDistortRGB(pm, r) applies a random distortion to the R, G, and B components of each pixel separately, and returns the result. Each R, G, and B component is shifted by at most r units of intensity. r is an integer between 1 and 255.