Optimizing Your Image Files

Getting the most out of your photos and graphics

Start with the smallest size that works.
The right size for an image on the Web is the smallest number of pixels that gets the job done. The greatest contributor to image file size is the actual number of pixels to be reproduced.
Sometimes you can get a more effective image just by cropping more closely around the subject.
Limit the number of colors used.
Fewer colors means less information for each pixel, thus a smaller file. If you can work in sixteen colors, your files will be tiny and reproduce well on almost any monitor. In no case should you use more than 256 colors without a very good reason.
In the case of photographs, you can often reduce a full-color image to 256 colors with little or no noticeable degradation and a large reduction in file size. Just reduce from full-color to 256-color, then right back to full color, then save as JPEG.
Eliminate unneeded complexity.
Both GIF and JPEG files use compression, and a large area of one color will compress much more than the same area with a lot of detail. Photographs with lots of plants in them will be bigger than ones with simple backgrounds, for instance.
Use the right file type for the image.
Generally, the GIF format works best for computer-originated images, and JPEG best for photographs. But don't be afraid to experiment.
Avoid gray-scale photos if possible.
Contrary to what you'd think, it's harder to reproduce monochrome then color. Anything you can do to reduce the number of shades of gray will help.
You'll almost always get better results if the image contains some color, even false color.

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