Colormap Editing

Editing Colormaps

Why on earth would you want to?

There are several reasons for changing a colormap. True, it is usually inappropriate and results in ugly images, but there are times when a change is very helpful.

There are two different ways to alter a colormap. The first is the change values by hand. This is useful if you want every pixel that is one particular color to be another. For example, if you took a screenshot of a web-page, and you want to make the background a different color, you could re-map the background color to another one.

What about the other way?

False-color Gaussian hill

It turns out that the first method is not really used that frequently. The second method, however, is to re-map all pixels using a function, similar to the way the lighting applet does. These function maps can then be either used directly, or saved as palettes, which are basically color re-mapping files.

This is used quite often in fields such as medicine and astronomy to generate what are known as false-color images. Different brightness levels are mapped to hues, which is done very easily programmatically. Red might represent hot or high intensity radio signals, while blue and black could represent low intensity signals. When your "image" is just intensity levels, making a false-color image drastically improves readability, because the different hues are easier to see than the different shades of a similar black and white intensity image.

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