When we see a picture on our monitor or use our digital camera (or scanner), the image we are viewing or dealing with is not continuous like a pencil drawing – it is made up of many small elements next to each other. When we have enough elements, we get the illusion of a picture or image.

WHAT IS DIGITAL? Early digital images (before color) appeared in black and white. The tiny elements that comprised digital images were either black or white. These two ‘colors’ corresponded to 1 and 0 (called BITS or BI-nary digi-TS ). Digits 1 and 0 are used in the binary (base 2) system. Thus, a map (pattern) made up of these 1’s and 0’s was referred to as a bit-map. That was the early digital image.

TODAY’S BIT-MAPS: Today we have BMP (Windows bit-map) files. You may have a BMP image on your desktop as wallpaper (it is probably a color image). Another similar bit-map file is a TIFF (Tag Image File Format – file extension .TIF).

STRUCTURE OF BITMAPS: All digital images are a rectangle or square. Today, the elements are called pixels (Picture Elements – see article What is a Pixel). The illustration below shows a simple "smiley" digital image made up of color pixels (for illustration only – not real size). The white area of the image is filled with white pixel squares.

The digital image illustrated above is how it would appear in an image editor like Photoshop at 800% enlargement – you would see the individual pixels. However, the actual 28 x 28 pixel smiley viewed on a monitor would appear as a small icon (see below). In the real world, pixels are so small and close together that you see a "picture."

© 2004 Fred Hall