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Unlike Exchange filter, Map Color Range maps a defined color range against another defined color range.
Preview: This Preview displays color changes interactively, before they are applied to Image.
The two Color Swatch Boxes allow you to define From and To limits of source color range. When you click on a box, you call the Color selector of Gimp.
The two Color Swatch Boxes allow you to define From and To limits of destination color range. When you click on a box, you call the Color selector of Gimp.