Adobe 29180155 User Guide - Page 271

ADOBE PHOTOSHOP ELEMENTS 4.0 266 User Guide Web button without transparency (left) and with transparency (right) Background matting, supported by the GIF, PNG, and JPEG formats, simulates transparency by filling or blending transparent pixels with a matte color that matches the web page background. Background matting works best if the web page background is a solid color and if you know what that color is. To create background transparency or background matting in the optimized image, you must start with an image that contains transparency. You can create transparency when you create a new layer or use the eraser tools. When working with GIF or PNG-8 files, you can create hard-edged transparency: All pixels that are more than 50% transparent in the original image are fully transparent in the optimized image, and all pixels that are more than 50% opaque in the original image are fully opaque in the optimized image. Use hard-edged transparency when you don't know the background color of a web page, or when the web page background contains a texture or pattern. However, keep in mind that hard-edged transparency can cause jagged edges in the image. GIF without hard-edges transparency (left) and with hard-edged transparency (right) See also "Adding layers" on page 83 "Optimized file formats for the web" on page 259 "To create hard-edges transparency in a GIF or PNG-8 file" on page 267