XAddPixel The XAddPixel() function adds a constant value to every pixel in an image. It is useful when you have a base pixel value from allocating color resources and need to manipulate the image to that form.
Specifies the image.
Specifies the constant value that is to be added.
XAddPixel(), XCreateImage(), XGetPixel(), XPutPixel(), XSubImage(), http://tronche.com/gui/x/xlib/utilities/manipulating-images.html
See Implementation
XAddPixel The XAddPixel() function adds a constant value to every pixel in an image. It is useful when you have a base pixel value from allocating color resources and need to manipulate the image to that form.