If you've ever saved JPEG at its lowest quality setting just to get a super-small file size, but wished you could have forced that low quality to only be in certain places of the image, here's your answer: weighted optimization. By deliberately weighting the optimization of certain key settings in Photoshop or ImageReady, you can control where optimization occurs.
For example, in JPEGs you can control where quality is lost. You can also control where dithering occurs in GIF, PNG-8, and WBMP dithering, and which areas of a GIF are more lossy than others. Finally, for GIF and PNG-8 images, you can use weighted optimization to specify which areas of color are most important and therefore shouldn't be dropped from the color table.
Weighted optimization uses masks to tell the program which areas are more important than others. Masks can be derived from outlines around text on type layers, outlines around vector shapes on shape layers, saved selections, or any other mask saved in the Channels palette.
TRY IT To use weighted optimization, make sure the file with which you want to work is open and the mask you want to use is available. In other words, make sure the area you want to designate as being most important is one of the following:
• Saved as a mask in the Channels palette
If it is not one of the preceding, then, with the selection tools, make a selection around the area you want to carry the most weight during optimization. Choose Select | Save Selection and give it an appropriate name.
Next, in Photoshop choose File | Save For Web to access the optimization settings for the file. In
ImageReady click the Optimized tab and choose Window | Optimize to view the
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