ESL's graphical regions are vector-based graphics, in which images are created by describing them as line segments forming shapes on the screen.  As the instructions required to create an image are embedded into the ESL application, there are no additional files needed to distribute. File images, by contrast, are created by describing the image, typically as a grid of positions (pixels) each having a color value, or being either on or off, for monochrome images. File images require significantly more space on both disk and within random access memory. Although compiled bitmap images are stored within the ESL application, the original files will be needed at runtime for the resizing of an image region.