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Graphic Image Compression
Why optimize?
We all get twitchy when we have to wait for web pages to download. Graphics are usually the biggest elements in file size so be sparing with them and keep them skinny!
Two common file compression schemes for graphics are GIF and JPEG. Image-editing programs should have the option of saving in these formats but, if you don't have that option, check for shareware programs online that you can download. Some ideas of where to look are on the Resources page.
Typically GIF works best with small graphics and JPEG with photos - but not always!
GIF depends on reducing the color palette of a given image to the smallest number of colors. You can control how many colors are used and decide how much you can reduce them and still get a good image. Because you are limiting the palette, GIFs start to look dithered quickly. This isn't a problem with single-color square graphics.
An image saved as a GIF with 256 colors. The image is 12K.
The same image saved as a GIF with eight colors. Now the graphic has some dithering. This image is 8K.
JPEG compresses file size by looking for long runs of single-pixel-high colors. A solid blue sky is a good example. It then remembers mathematically how many pixels were that one color rather then remembering each pixel individually.
The same image saved as a JPEG. This is also 12K but looks better than the GIF above.
Try to balance your best image with the smallest possible file size.
Website design, graphics and content by Julie Ann James
Copyright® Julie Ann James Design, 1999
Graphic Image Compression
Why optimize?
We all get twitchy when we have to wait for web pages to download. Graphics are usually the biggest elements in file size so be sparing with them and keep them skinny!
Two common file compression schemes for graphics are GIF and JPEG. Image-editing programs should have the option of saving in these formats but, if you don't have that option, check for shareware programs online that you can download. Some ideas of where to look are on the Resources page.
Typically GIF works best with small graphics and JPEG with photos - but not always!
GIF depends on reducing the color palette of a given image to the smallest number of colors. You can control how many colors are used and decide how much you can reduce them and still get a good image. Because you are limiting the palette, GIFs start to look dithered quickly. This isn't a problem with single-color square graphics.
An image saved as a GIF with 256 colors. The image is 12K.
The same image saved as a GIF with eight colors. Now the graphic has some dithering. This image is 8K.
JPEG compresses file size by looking for long runs of single-pixel-high colors. A solid blue sky is a good example. It then remembers mathematically how many pixels were that one color rather then remembering each pixel individually.
The same image saved as a JPEG. This is also 12K but looks better than the GIF above.
Try to balance your best image with the smallest possible file size.
Copyright® Julie Ann James Design, 1999