Adjusts the colour saturation of image files (PNG, JPG, TIFF and other formats
supported by Pillow). The factor controls the strength: 0.0 produces a
greyscale image, 1.0 leaves the image unchanged, and values above 1.0increase saturation (a useful range is roughly 0.0–2.0). A factor of1.5, for example, increases colour saturation by about 50%.
Files that are not images are passed through unchanged.