Give Images a Tighter Shave

Posted: December 8th, 2004
Filed under: Web Speed and Performance

When attempting to optimize Web site performance, it is obvious to look towards dependent objects like images and other media files like Flash for the bulk of the download (and thus transfer delay). Today’s Web developers are familiar on using Photoshop or Fireworks to optimize images — for example, reducing the colors in GIF images or reducing the % quality in JPEG images — but even after doing this, there is often junk lying around in the file. For example, in JPEG images, extra information like

– Digital camera technical data (EXIF)
– Comment and application blocks
– Thumbnail information

may add more data to our your image file/picture than most human and normal end users would care about. For example, when we stripped some of the images being used on our site (noticeable savings, though not enormous savings), we shaved about 2.5K off one image (17Kb to 14.5Kb) just by running it through an image stripper like PureJPG:

While this is not tremendous savings, every little bit helps, and since it does not distort the image at all, we have already speced this feature for an upcoming release of w3compiler. Some folks might ask why we don’t do image crunching like this in our server products: we could, but the performance impact can be significant. However, we’d be happy to hear from anybody who thinks this approach makes sense for httpZip as well…

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