Change Gray Values

This method allows the greatest flexibility in setting the brightness of grayscale images. A graph is displayed showing the relationship between pixel value and intensity for the selected image.

For color images, use "Change Colors" instead.

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 change. 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 brightness settings will be applied to the image. If you click ``Accept'' without clicking ``Finished'', the image will not be changed.
4. 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.