When drawing complex graphic images, a common technique in graphics programming is to create an off-screen bitmap, draw the image on the bitmap, and then copy the complete image from the bitmap to the final destination onscreen. Using an off-screen image reduces flicker caused by repeated drawing directly to the screen. 

The bitmap class in Delphi, which represents bitmapped images in resources and files, can also work as an off-screen image. 

There are two main aspects to working with off-screen bitmaps:

• Creating and managing off-screen bitmaps.
• Copying bitmapped images.