9.3. Distance Map
| 9. 通用滤镜 |

### 9.3. Distance Map

#### 9.3.1. Overview

Each pixel in the image is replaced with a gray value dependent on the distance to the nearest obstacle pixel, generally a boundary pixel. Different methods can be used to calculate the distance.

#### 9.3.2. Activating the filter

This filter is found in the image window menu under Filters → Generic → Distance Map….

#### 9.3.3. Options

图 17.167. “Distance Map” options

Presets, Preview, Split view

  | 注意
  These options are described in 第 2 节 “Common Features”.

Metric

  “Metric” is a topology term. Three methods are available:

  - Euclidean default: the distance is a line.

  - Manhattan

  - Chebyshev

Threshold low

  Default is 0. Increasing this value selects higher lightness pixels

  Original image for examples. Threshold low will be progressively increased. Lightness: dark red = 0.070; bright red = 0.223; green = 0.133

  图 17.168. “Threshold low” example

  Threshold low = 0: only border distances are visible.

  Threshold low = 0.070: “dark red” circle appears.

  Threshold low = 0.133: “green” circle appears.

  Threshold low = 0.223: “bright red” circle appears.

Threshold high

  Default is 100. Decreasing this value makes result lighter.

Grayscale Averaging

  Number of computations for grayscale averaging.

Normalize

  This option is checked by default. If you uncheck it, no blur is created.

  图 17.169. “Normalize” example

  Normalize option checked.

  Normalize option unchecked.

#### 9.3.4. Using Distance Map filter

Searching for an example using Distance map filter in image processing...

9.2. Convolution Matrix |  | 9.4. GEGL graph

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