The Normalize command, except that it works on each color channel of the layer individually. This usually leads to color shifts in the image, so it may not produce the desired result. ΓÇ£Stretch ContrastΓÇ¥ works on layers of RGB, Grayscale and Indexed images. Use ΓÇ£Stretch ContrastΓÇ¥ only if you want to remove an undesirable color tint from an image which should contain pure white and pure black.
command automatically stretches the histogram values in the active layer. For each channel of the active layer, it finds the minimum and maximum values and uses them to stretch the Red, Green and Blue histograms to the full contrast range. The bright colors become brighter and the dark colors become darker, which increases the contrast. This command produces a somewhat similar effect to theThis command is also similar to the White Balance command, but it does not reject any of the very dark or very bright pixels, so the white might be impure.
This command can be accessed from an image menubar as
→ → → .Figure 15.94.  Original image
The layer and its Red, Green and Blue histograms before ΓÇ£Stretch ContrastΓÇ¥.
Figure 15.95.  Image after the command
The layer and its Red and Green and Blue histograms after ΓÇ£Stretch ContrastΓÇ¥. The pixel columns do not reach the right end of the histogram (255) because of a few very bright pixels, unlike ΓÇ£White BalanceΓÇ¥.
Histogram stretching creates gaps between the pixel columns, giving it a striped look.