Using masks to modify color reduction

When you use mask to optimize the colors in a GIF or PNG-8 image, the white areas of the masks indicate to the color reduction algorithm which pixels are highly important, whereas black areas of the masks indicate which pixels are less important.

To use masks to modify color reduction:

1. In the Optimize panel/palette, choose a GIF or PNG-8 setting from the Settings menu, or choose GIF or PNG-8 from the file format menu.
2. Choose a color reduction algorithm and specify the maximum number of colors.
3. Click the mask button to the right of the Color Reduction Algorithm pop-up menu.
4. Choose which masks to use:
• All Text Layers to use the masks from all text layers in the image.
• All Vector Shape Layers to use the masks from all shape layers in the image.
• Channel to choose an alpha channel from the menu. In ImageReady, you can choose Save Selection to create a new alpha channel based on the current selection.
5. To preview the results of the weighted optimization, select the Preview option.
6. Click OK.