REDUCING COLORS
WHY AND HOW
An Image Magick Tute by Flo |
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WHY REDUCE COLORS? Color jpeg (jpg) images, especially photographs, have thousands and thousands of colors. On the other hand, gif images have around 256 colors or less. Image Magick has some features, such as Transform/Unique Colors (please see links to tutorials below), that will not work at all on images that have very large numbers of colors (photographs). So if we want to use those special features, we must first reduce the color numbers of those images.
Also, another reason for reducing colors is to reduce the image's file size for storage. | |
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Original: 35,209 colors. I could not use Unique Colors. (pop-up)
After Colormap reduce: 31,877 colors. Now I could use Unique Colors.
Finished image is below the original. | |
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- Change colors to 10
- Check Dither
- Check Netscape
- Use Identify to check color numbers
- Use Unique Colors
- Composite/Lighten
NOTE: Now there is an easier way to use UC with jpgs that are not photographs - Please click on Flo's Unique Colors with JPGs tute |
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HOW TO REDUCE COLORS First Input a jpg or gif into the IM of your choice. Go to the tab in the top row next to the View tab - Identify. On the next screen, scroll down beyond Channel Statistics to find Colors: 50000 or some such figure.
Now scroll up and click on the Colormap tab, also in the top row.
- In the box you'll see 256. Delete and type in a lower number. I have gotten best results with 10 to 20.
- Uncheck Dither (CaliKat's advice). Check Netscape Color Cube.
- Click on the Quantize button.
- On the View page, again click on the Identify tab and check the number of colors. My best results, using Unique Colors have been when the color numbers get down to around 30,000. CaliKat has been successful with a 69000-color jpg reduced to 256 colors. You will have to experiment, as each jpg is different.
If you wish to use the Transform/Unique Colors feature, please make sure you look at CaliKat's Examples page, and the two Unique Colors tutorials, links below. | |
| Here is CaliKat's Examples page, showing how the Unique Colors results change according to the number of colors we reduce a jpg to in Colormap. |
Choco's Unique Colors tute
CaliKat's Make Your Own Unique Colors tute
These two tutes are the first ones written (August, 2006)
on the new Transform/Unique Colors feature.
Flo's Unique Colors with JPGs tute
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