GeoExpress displays the histogram for an image on the left side of the Color Balance Manager. The histogram control enables you to adjust the minimum, maximum, and gamma values for each band in the image.
The black slider represents the minimum pixel value, the white slider represents the maximum pixel value, and the gray slider represents the gamma value. The range of values for the minimum and maximum controls is based on the data type of the image. For example, for 8-bit images, the range of values is 0 through 255. The maximum value cannot be less than or equal to the minimum value.
The gamma slider is restricted to a fractional position in between the minimum and maximum sliders. The range of gamma values is 0.102 – 9.99. The default value of 1.0.
The histogram controls adjust dynamically as the brightness and contrast values are changed.
To revert back to an image’s original state, removing all color corrections, click Reset All Corrections.
Below the histogram control are two slider controls for modifying the brightness and contrast of the active band of the image. They accept integer values from -100 to 100, -100 being low brightness/contrast and 100 being high brightness/contrast. The histogram controls adjust dynamically as the brightness and contrast are changed.
The "Enable Live Updating" check box controls how the preview image is updated. If "Enable Live Updating" is selected, the image will update in real time as you manipulate the slider controls. If the update performance starts to slow down, as it may for very large mosaics, you can clear this check box to disable the live updating feature so that the image only updates after a dragging operation is complete (i.e. when the mouse button is released).