• CLUT / contrast slider can increase the contrast.
• CLUT / dimmer slider can increase, decrease, and reverse the contrast.   It acts like the contrast slider within the middle portion of the range - the wings behave differently to allow decrease or reversal of contrast.
• CLUT / display CLUT shows a color bar for any of the CLUT sliders.

Notes about other software:

• ImageJ, Image / Adjust / Brightness & Contrast allows increase and decrease of contrast, but not reversal.  Use Image / Lookup Tables / Invert LUT to reverse the contrast.
• Photoshop, Image / Adjust / Levels allows contrast increase, decrease and reversal.  The outer two of the upper sliders (see picture of the levels dialog) increase the contrast.  The middle one of these adjusts the gamma.  The two sliders below the output levels bar decrease the contrast.