Adobe 13101332 - Photoshop - Mac User Manual page 430

Adobe Photoshop Help
Using Help | Contents
To use masks to modify dithering:
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 Click the mask button
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 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 dithering range:
To set the highest percentage of dithering, drag the right (white) tab on the slider, enter
•
a value in the Maximum text box, or use the arrows to change the current percentage.
To set the lowest percentage of dithering, drag the left (black) tab on the slider, enter a
•
value in the Minimum text box, or use the arrows to change the current percentage.
6 Click OK.
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
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.
Using Help | Contents
| Index
to the right of the Dither text box.
to the right of the Color Reduction Algorithm pop-up menu.
| Index
Preparing Graphics for the Web
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