Change colors

This method allows the greatest flexibility in setting the brightness. A 3-part graph is displayed showing the relationship between pixel value and intensity for red, green, and blue.

Tnimage differs from some other programs in that color editing is done in full 24-bit mode for 24 bit/pixel images, rather than simply converting the image to an 8-bit indexed image. In no case does tnimage simply take the shortcut of altering the colormap for true color iamges, which would cause tremendous loss of image color detail.

For grayscale images, use "Change Gray Values" instead; or use ``change gray values'' instead or select `Color | Convert to color' before proceeding.

Procedure

1. Click ``Image..Backup'' or press Ctrl-B to backup the image before starting.
2. Click the left mouse button in the graph to create a curve which defines the desired mapping of pixel value to color. This will create small boxes (control points) which can be repositioned within the graph by dragging them. Each time you click, a new point is added.
3. Click the `Finished' button on the lower left of the graph window when you are satisfied with the new curve. The graph will then be redrawn and the new color settings will be applied to the image. If you click ``Accept'' without clicking ``Finished'', the image will not be changed.
4. Repeat with other colors as desired. The graph can also be smoothed, saved to disk, etc. by clicking on the other buttons at the left of the graph. The Automatic Baseline button and a few other buttons are disabled. See 7.10.2 for more information about the buttons at left.

For 8 bit/pixel modes, the colormap (palette) of the image is changed and the pixel values in the original image are unaffected. It is not possible to change the color of only part of the image for 8 bit images with this method. To change only a portion of an image, you must convert the image to 24 bits/pixel first.