LUT: Some controls change the way your image appears, but without actually modifying the pixel values in your image bitmap.  Instead, the controls modify a Lookup Table (LUT) through which your image is interpreted.   For example, when you increase brightness in an image, all of the intensity values in your image are increased by a certain amount.  The pixel values in your image are not actually changed; the changes you see on the screen are calculated by reading the image's original value and processing it through the Lookup Table.  

The following image adjustment options modify the LUT for the image:

• The Brightness, Contrast, and Gamma controls
• The Contrast Enhancement option
• The Equalize options, or
• The Invert Contrast option.

When contrast has been applied to your image, but you have not saved the image, an asterisk will appear next to the name of the image in the image workspace title bar and status bar.