Source string usage details

Alpha toning is an advanced method of greyscaling or colorizing. It works using transparency, not colour matching. The results of this filter are excellent for using as watermarks, and for 'sepia' type imprints on coloured or textured backgrounds. It converts dark areas of the image to opaque, light to transparent.

Note that if you are working with JPEGs, this alpha effect will not last into the final image unless you either flatten this image against a background color or image in a later process or convert it to a PNG before saving using available image effects.