Changes the raw pixel values in an image or selected region. ``Change pixel value'' is particularly useful for making grayscale images lighter or darker. It allows precise changes to be made to the brightness level. The effect is consistent across all image types and screen modes but behaves differently for color and grayscale images.
For grayscale images:
This adds a value to all pixels in the currently-selected image or screen region, making it darker or lighter. Works in conjunction with `Grayscale map'.
For color images:
This adds or subtracts a value for the red, green, and blue components of the currently-selected image or screen region, making it darker or lighter or altering its color balance.