Using masks to modify GIF lossiness

When you use masks to optimize the amount of lossiness (or quality reduction) in a GIF image, white areas of the masks yield the highest quality, and black areas of the masks yield the lowest quality. You can adjust the maximum and minimum level of quality reduction in the Modify Lossiness Setting dialog box.

To use masks to modify GIF lossiness:

1. In the Optimize panel/palette, choose a GIF setting from the Settings menu, or choose GIF from the file format menu.
2. Click the mask button to the right of the Lossy text box.
3. 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.
4. To preview the results of the weighted optimization, select the Preview option.
5. Define the quality range:
• To set the highest level of quality, drag the left (white) tab on the slider, enter a value in the Minimum text box, or use the arrows to change the current value.
• To set the lowest level of quality, drag the right (black) tab on the slider, enter a value in the Maximum text box, or use the arrows to change the current value.

Note: Lossiness is a reduction in quality; therefore, the highest level of image quality is defined by the Minimum value, and the lowest level of image quality is defined by the Maximum value. This is the opposite of the JPEG quality setting.

6. Click OK.