Developer

Learn how to modify a GIF

When you need to add something to a GIF image, it's often difficult to get the exact color that you want. Find out how properly modify a GIF.

By Paul Anderson

When you need to add something to a GIF image—say, an outline or your company logo—it's often difficult to get the exact color that you want. Even after you adjust your image editor's color picker to the tone you want, it might give you another.

This problem comes up because the image editor sticks to the GIF's color palette and you're trying to use a color that isn't in the palette. The solution is to open the GIF and change it to true color (RGB). Now you'll have access to any color you want. After you've modified the image, reduce it back to 8-bit or lower so that you can resave it as a GIF.

Even if you don't need to add new colors, watch to see if your modifications remove any colors, especially if you crop the GIF. Because every color removed from the palette helps shrink the file size—especially if it reduces the bit depth—take the opportunity to have your image editor recount the colors. Some image editors require you to switch to true color first, but when you go back to indexed color the palette may be smaller.

You can avoid these issues if you just want to replace one color with another. With the GIF still in indexed color mode, open the palette (look for Palette or Color Table in your image editor's menus) and click the color that you want to change. Enter the RGB values for the new color, then close the palette. Every pixel that was in the old color will now be in the new one.

Paul Anderson is associate technical editor for CNET Builder.com. His responsibilities don't include handling graphics, so naturally, he handles them all the time.

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