Brightness/contrast
Change the brightness and contrast by pressing the mouse button with the
brightness/contrast tool and moving the mouse horizontally and vertically. The brightness
and contrast values are displayed in the bottom right corner of the image
window.
The viewer has an automatic brightness/contrast function, stretching. Press the stretch
button in the toolbar to see what the viewer calculates as the best brightness and contrast
for the particular image or scene.
Press the 'Reset brightness/contrast' button in the toolbar to reset to the
default values.

Brightness/contrast with the right mouse button