The Win32 API includes a number of functions that retrieve information from an image list. The ImageList_GetImageInfo function fills an IMAGEINFO structure with information about a single image, including the handles of the image and mask bitmaps, the number of color planes and bits per pixel, and the bounding rectangle of the image within the image bitmap. You can use this information to directly manipulate the bitmaps for the image.
The ImageList_GetImageCount function retrieves the number of images in an image list.