8.18. Stretch Contrast
| 8. The “Colors” Menu |

### 8.18. Stretch Contrast

The Stretch Contrast 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. “Stretch Contrast” works on layers of RGB, Grayscale and Indexed images. Use “Stretch Contrast” only if you want to remove an undesirable color tint from an image which should contain pure white and pure black.

This command is also similar to the Color Balance command, but it does not reject any of the very dark or very bright pixels, so the white might be impure.

#### 8.18.1. Activating the Command

- You can access this command from the main menu through Colors → Auto → Stretch Contrast.

#### 8.18.2. Options

图 16.161. “Stretch Contrast” settings

Presets

  “Presets” are a common feature for several Colors commands. You can find its description in 第 8.1.1 节 “Colors Common Features”.

Keep Colors

  Impact each color channel with the same amount.

Non-Linear Components

  When set, this option operates on gamma corrected values instead of linear RGB.

Blending Options, Preview, Merge filter, Split view

  These are common features described in 第 8.1.1 节 “Colors Common Features”.

#### 8.18.3. “Stretch Contrast” Example

图 16.162. Original image

The layer and its Red, Green and Blue histograms before “Stretch Contrast”.

图 16.163. Image after the command

The layer and its Red and Green and Blue histograms after “Stretch Contrast”. The pixel columns do not reach the right end of the histogram (255) because of a few very bright pixels, unlike “White Balance”.

Histogram stretching creates gaps between the pixel columns, giving it a striped look.

8.17. White Balance |  | 8.19. Stretch Contrast HSV

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