These types of drawing programs allow the designer to refine details, make dramatic changes with special effects options, and are noted for providing a greater degree of subtly than vector based graphics. These images can be transformed by using image editing filters to create a wide range of special effects and natural looks. These programs work with pixels or bitmapped images that can be enhanced with vector style painting options. Lets take a moment and give you an overview of what a bitmap is and what it does. Bitmap is a collection of picture elements or dots, also known as pixels.
Bitmapped images are resolution-dependent.
Basically this means you must specify a resolution. If you create the image and then change the resolution youde-grade the image. Scaling up can be a real disaster, scaling the image smaller sometimes yields better results. Raster Illustrations - notice the degredation in quality as the image is increased in size. Bitmapped images are resolution dependent, best used with continuous tone images like photographs and can be modified with great detail because you can manipulate each pixel.