Remember that if you choose to use PNG-24 to achieve variable transparency, many users won't be able to see it because their browsers don't yet fully support PNG files. (The latest versions of Internet Explorer and Netscape do support PNG files without plug-ins, but not the variable transparency aspect.) To check out which browsers do support PNG, and to what extent, visit www.libpng.org/pub/ png/pngapbr.html.
TRY IT To optimize transparent web graphics, make sure you have the file you want to optimize open in Photoshop or ImageReady. If necessary, turn off the Background layer of the file to make the transparent parts of the image visible. Then, in Photoshop choose Save For Web. In ImageReady choose Window I Optimize to view the Optimize palette.
Select GIF, PNG-8, or PNG-24 from the File Type menu depending on which type of transparency and which file format you want to use. Place a check mark in the box next to Transparency and click the color sample box to the right to specify the background color of your web page (against which the image will be placed).
To force a certain color in the image to be transparent, first use the Eyedropper tool to select that color from the image. Then click the first button below the Color Table to "make transparent."
For GIF and PNG-8 you have several additional options related to the dithering of soft edges during the transition to transparency. These are discussed in the following tip.
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Adobe Photoshop can be a complex tool only because you can do so much with it, however for in this video series, we're going to keep it as simple as possible. In fact, in this video you'll see an overview of the few tools and Adobe Photoshop features we will use. When you see this video, you'll see how you can do so much with so few features, but you'll learn how to use them in depth in the future videos.