5.10. Desaturate
| 5. 色ツール |

### 5.10. 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.

| 注記
This command only works on layers of RGB images. If the image is in Grayscale or Indexed mode, it can do nothing.

#### 5.10.1. Activating the Command

You can get to this tools in several ways:

- In the image menu through Tools → Color Tools → Desaturate or Colors → Desaturate,

- by clicking on the tool icon in Toolbox, if this tool has been installed there.For this, please refer to 「Toolbox」.

#### 5.10.2. Options

図14.175 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 + 0.72 × G + 0.07 × B
Average

  The graylevel will be calculated as

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

図14.176 Comparing the three options

Original image

「Lightness」 applied

「Luminosity」 applied.

「Average」 applied.

5.9. Posterize |  | 6. その他のツール

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