9
Editing a Colour Palette
When you open an 8-bit original image, the palette for that image displays in the Optimized Colours palette
in ImageReady. You can then choose a palette type in the Optimize palette and switch to the optimised view
of the image to check the effects of this palette. If you select the Web palette, ImageReady automatically
reduces the palette to only the number of colours in use (120 out of 256, for example). With other palettes,
you can reduce them yourself, convert colours to Web-safe equivalents, lock colours so that they won’t be lost
in the reduction process, or even add different colours. As you work, you can check the effect of your choices
on your final image in the LiveView window.
Try it:
1. Choose File > Open > banner.ai.
2. Click the Optimized tab to view a 256-colour Perceptual palette for this illustration (if necessary, choose
Window > Show Colour Table and position the Optimized Colors palette near the Optimize palette).
3. Switch back and forth between the Optimized and Original views to note how well the Perceptual palette
maintains the colours in the illustration. Note that the estimated file size is high for a Web graphic.
4. Make sure you’re looking at the Optimized image. Then select the eyedropper tool from the toolbox.
5. Click dominant colours in the image. For example, click the rust colour in the tree at the left end of the
banner. Note that the corresponding colour is highlighted in the Optimized Colours palette.
6. Click the lock symbol at the bottom of the Optimized Colours palette to lock the rust colour. Then con-
tinue selecting and locking the colours that you want to preserve in the palette.
7. When you’ve finished locking the key colours, choose 128 from the Colours pop-up menu in the Optimize
palette. Note that the overall colour quality stays level, while the file size drops by several K .
8. Check for any dithering problems on an 8-bit display by choosing View > Browser Dither. Note that the
blue-green in one of the skyscrapers shows a lot of dither.
9. Choose View > Browser Dither again to turn off the effect. Then use the eyedropper tool to
sample the blue-green colour. The Optimized Colors palette highlights the colour.
10. Click the cube button at the bottom of the palette to shift this colour to its nearest Web-safe
equivalent and prevent on-screen dither. A dot now appears in the centre of the colour swatch
to indicate that it’s a Web-safe colour.
You can double-click the colour to view it in the Colour Picker and compare the previous colour
with the Web-safe equivalent.
The lower-right corner of the
swatch changes to indicate that
you’ve locked the colour.
The dot in the center of the swatch
indicates that you’ve “Web-shifted”
a color.