Add
Purpose: Adds a value from each channel of each pixel of the image. Two modes:
- value: Adds the value from every channel value of every pixel in the image.
Remember, the internal working image is floating point, 0.0 - 1.0, so meaningful subtractions
are with numbers in that range. But, you can do what you want... :D Actually, I don't know
what practical use this mode might be...
- file: Opens the selected image file, and adds every corresponding channel value of
every pixel of it from the working image. Unlike subtract, add will allow a smaller image,
oriented to one of the four corners: topleft, topright, bottomleft, bottomright. This mode
is useful for adding watermarks to images, where the image to be added is a black-background,
white-text image formatted to display nicely in one of the corners.

Properties: See tool.add.* in Configuration Properties