11.3. Desaturate

11.3. Desaturate
	11. The “Colors” Menu

Revision History
Revision $Revision: 2342 $	2008-01-21	ude

By using the Desaturate command, you can convert all of the colors on the active layer to corresponding shades of gray. This differs from converting the image to grayscale in two respects. First, it only operates on the active layer and second, the colors on the layer are still RGB values with three components. This means that you can paint on the layer, or individual parts of it, using color at a later time.

	Note
	This command only works on layers of RGB images. If the image is in Grayscale or Indexed mode, the menu entry is insensitive and grayed out.

11.3.1. Activate the Command

You can access this command from the image menubar through Colors → Desaturate.

11.3.2. Options

With GIMP v2.4, a new option dialog appeared:

Figure 15.134. The “Desaturate” option dialog

Three options are available:

Choose shade of gray based on

Lightness: The graylevel will be calculated as

Lightness = ½ * (max(R,G,B) + min(R,G,B))
Luminosity: The graylevel will be calculated as

Luminosity = 0.21 * R + 0.71 * G + 0.07 * B
Average: The graylevel will be calculated as

Average Brightness = (R + G + B) / 3

Figure 15.135. Comparing the three options

Original image

“Lightness” applied

“Luminosity” applied. The result is brighter.

“Average” applied. The result is in between Brightness and Luminosity.