8.14. Value Propagate
| 8. Distort Filters |

### 8.14. Value Propagate

Revision History
Revision $Revision: 2440 $ | 2007-05-05 | j.h

#### 8.14.1. Overview

Figure 16.135. Example for the Value Propagate filter

Original image

Filter “Value Propagate” applied

You can find this filter through Filters → Distorts → Value Propagate.

It works on color borders. It spreads pixels that have a Value between selected thresholds, in selected directions.

#### 8.14.2. Options

Figure 16.136. “Value propagate” filter options

Preview

  The result of your settings will appear in the Preview without affecting the image until you click on OK.

Propagate Mode

  The examples will be about the following image (zoom x8):

  Figure 16.137. Original image

  - More White: Pixels will be propagated from upper Value pixels towards lower Value pixels. So bright areas will enlarge.

    Figure 16.138. More White

    Bright pixels have been propagated to dark pixels in the four directions : top, bottom, right and left. Filter applied several times to increase effect.

  - More Black: Pixels will be propagated from lower Value pixels towards upper Value pixels. So dark areas will enlarge.

    Figure 16.139. More Black

    Figure 16.140. To bottom only

    The same as above with To bottom direction only checked.

  - Middle Value to Peaks: On a border between the selected thresholds, the average of both values is propagated.

    Figure 16.141. Middle Value to Peaks

    A thin border with a transitional color has been added to objects. It is not visible around objects with smoothed borders.

    Green area zoomed x800. A thin border (one pixel wide) has been added. Its value is the average between grey (90%) and green (78%) : (90 + 78) / 2 = 84.

  - Foreground to Peaks: The propagated areas will be filled with the foreground color of the toolbox.

    Figure 16.142. Foreground to Peaks

    In this example, the foreground color in Toolbox is Red. A thin border, one pixel wide, red, is added around objects. With smoothed objects, this border is located at the furthest limit of smoothing. Here, another border appears inside. This is an artefact due to the small size of the object which makes the smooting area of opposite sides to overlap.

  - Only Foreground: Only areas with the Toolbox Foreground color will propagate.

    Figure 16.143. Only Foreground

    In this example, the foreground color in Toolbox is that of the green object. After applying filter several times, the green area is clearly enlarged.

  - Only Background: Only areas with the Background color will propagate.

  - More Opaque and More Transparent: These commands work like More White and More Black. Opaque (transparent) areas will be propagated over less opaque (transparent) areas. These commands need an image with an Alpha channel.

    Figure 16.144. More opaque

    Original layer, with a transparent background.

    Filter applied several times: the green, opaque, area got increased.

Parameters Settings
  Lower / Upper Threshold

    Lower Threshold and Upper Threshold: These commands allow you to set the Value range that will be concerned by Propagate.

  Propagating Rate

    Propagating Rate: That's the propagating amount. The higher it will be the more colored the propagation will be.

  Propagating Direction

    Propagating Direction: You can select one or more directions.

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