Image Compression Techniques

One of the most important aspects of your website is the amount of space required for its files. In addition to filling up a limited amount of space, large files (especially graphics) take longer to load and therefore people viewing your page must wait longer to see the pictures. There are, however, ways to make graphics files take up less disk space and therefore require less time to load and display.

The easiest way to reduce the size of the image file is to reduce the size of the image itself. By shrinking (not just scaling) the size of the image, fewer pixels need to be stored and consequently the file will take less time to load. Other methods of image compression are specific to the type of image:

Lossless GIF Compression

Reduce the number of colors, which reduces the size of the palette stored and makes LZW compression more effective
LZW Compression: Finds repeated patterns of colors in the image and stores the color and number of repeated pixels instead of each individual pixel

Lossy JPEG Compression

JPEG Compression Algorithm: The algorithm searches the picture for variations, which are stored instead of actual pixels
Reducing the colors in the image may actually hinder the JPEG compression process
As the amount of compression increases, the quality of the image decreases