A brief tutorial of Image types.

This is a short tutorial that describes the difference between the three most common types of images.
The three types we are interested in are:

Bitmaps
Windows Images. The Largest of the image types.
24bit Color (Approx. 16 million colors available).
GIFs
Graphics Image Format. Used for animation and line art.
8bit Color (256 colors available).
JPEGs
Used on the Net for Photos. Compressed Bitmaps.
24bit Color.

When discussing images, it is important to make a clear distinction between Photos and Line Art. One is Rendered and the other is Created. The two images below illustrate this point. Image A is a photo and was rendered by a camera. Image B is line art and was created by me using Adobe PhotoShop.

Image A Image B

When an image is created or rendered it is usually created in the Bitmap format, referred to in many programs as RGB Mode. The letters RGB stand for the three basic colors used in computers, Red, Green, & Blue. Then one must decide what the contents are, and how many colors are used. Line art usually only uses a few colors.

The drawing in Image B above only uses about 30 colors if you include all the shades of gray, (which you have to). This is far less than 256 colors, so saving the image in GIF format is ok. This makes for a much smaller file. If you try to save Image A as a GIF, it will look terrible. Including all of the shades and light effects, Image A uses approximately 30,000 colors! So you would save that as a JPEG.

Table A below Illustrates this best. Look closely at the difference in quality with the photo, and the related file sizes. Hover over the images for a second to see my comments.

Table A
File Type: Bitmaps JPEGs GIFs
Photos: A Photo of me in BMP format. See how clear the image is. A Photo of me in JPEG format. See how the image still looks pretty clear but the file size has been cut in half. GIF format, as you can see, pretty poor quality for a photo.
File Sizes: 23Kb 11kb 4kb
Line Art: A drawing of my mascot 'Webster' in BMP format. Good quality. Webster in JPEG format. No noticable change but half the file size. Webster in GIF format. Still looks as good as the original, but check out the file size!
File Sizes: 23Kb 11kb 5kb
 
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©1999 Timothy Tobin