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JPEG Compression

The Joint Photographic Experts Group (JPEG) format features 16,777,216 colors, made up of 256 shades of red, 256 green and 256 blue (i.e. 256 cubed). Unlike GIF files, JPEG does not support transparency or animation.

 

JPEG is designed for photographs and naturalistic artwork.  GIF is the better choice for lettering, simple cartoons and line drawings. GIF Colors and Dithering is a prerequisite to this page, featuring more GIF and JPEG comparisons.

 

The following examples should help you decide how much compression you can apply to your JPEG photographs so that they load faster. Caution, the amount of acceptable compression will differ depending on the photograph. Notice how the sharp edge of the beak and the text smudges as the compression increases.

 

Under each example is the compression factor (ranging from 10 to 100) and the file size of the image. Without compression, the file size is 25,000 bytes (25 KB). Note, that the compression factor is a non linear arbitrary index and not a percentage.

 

The last example was saved in GIF format. Take a close look at the surface of the beak to see the GIF dithering. Each image is 150 x 140 pixels. For more JPEG and GIF examples go to the GIF Colors page.

10 -- 10.7 KB 20 -- 7.30 KB 30 -- 5.81 KB 40 -- 4.94 KB
50 -- 4.38 KB 60 -- 3.89 KB 70 -- 3.35 KB 80 -- 2.71 KB
 
90 -- 1.88 KB 100 -- 1.10 KB   GIF -- 12.1 KB