The ImageList_Replace and ImageList_ReplaceIcon functions replace an image in an image list with a new image. ImageList_Replace replaces an image with a bitmapped image and mask, and ImageList_ReplaceIcon replaces an image with an icon or cursor.
The ImageList_Merge function merges two images, storing the new image in a new image list. The new image is created by drawing the second image transparently over the first. The mask for the new image is the result of performing a logical OR operation on the bits of the masks for the two existing images.