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5.9. Desaturate

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] 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.

5.9.1. Activating the Command

You can get to this tools in several ways:

  • In the image menu through ToolsColor ToolsDesaturate or ColorsDesaturate,

  • by clicking on the tool icon in Toolbox, if this tool has been installed there (see Tools dialog.

5.9.2. Options

Figure 13.155. The “Desaturate” option dialog

The Desaturate option dialog

Three options are available:

Choose shade of gray based on


The graylevel will be calculated as

Lightness = ½ × (max(R,G,B) + min(R,G,B))

The graylevel will be calculated as

Luminosity = 0.21 × R + 0.71 × G + 0.07 × B

The graylevel will be calculated as

Average Brightness = (R + G + B) ÷ 3

Figure 13.156. Comparing the three options

Comparing the three options

Original image

Comparing the three options

Lightness” applied

Comparing the three options

Luminosity” applied.

Comparing the three options

Average” applied.

  Published under the terms of the GNU General Public License Design by Interspire