The Equalize command automatically adjusts the brightness of colors across the active layer so that the histogram for the Value channel is as nearly flat as possible, that is, so that each possible brightness value appears at about the same number of pixels as every other value. You can see this in the histograms in the example below, in that pixel colors which occur frequently in the image are stretched further apart than pixel colors which occur only rarely. The results of this command can vary quite a bit. Sometimes 「Equalize」 works very well to enhance the contrast in an image, bringing out details which were hard to see before. Other times, the results look very bad. It is a very powerful operation and it is worth trying to see if it will improve your image. It works on layers from RGB and Grayscale images. If the image is Indexed, the menu entry is disabled.

8.16.2. 「平滑化」の例

図16.149 元画像

「平滑化」適用前の活性レイヤーとその赤・緑・青各色のヒストグラム

図16.150 コマンド適用後の画像

適用後の活性レイヤーとその赤・緑・青各色のヒストグラム

Histogram stretching creates gaps between pixel columns giving it a striped look: colors that occur frequently are stretched.