Web Design in a Nutshell, 3rd Edition

Play with the “Loss” setting

As explained earlier in this chapter, GIF compression is “lossless,” meaning every pixel in the image is preserved during compression. The current web graphics tools allow you to force some pixels out during the conversion process using the “Loss” or “Lossy” setting. Throwing out stray pixels is all in the name of maximizing repeated strings of pixel colors, thus allowing the LZW compression to work more efficiently. Depending on the image, a loss value of 5 to 30% will maintain the integrity of the image while reducing file sizes significantly. This technique works best on images with areas of continuous tone (blended colors) and photographic content.