5.13. Value Propagate

5.13.1. Overview

图 17.84. Example for the Value Propagate filter

Example for the Value Propagate filter

Original image

Example for the Value Propagate filter

Filter “Value Propagate” applied

This filter works on color borders. It spreads pixels that differ in a specified way from their neighboring pixels.

5.13.2. Activating the filter

This filter is found in the image window menu under Filters → Distorts → Value Propagate….

5.13.3. Options

图 17.85. “Value propagate” filter options

“Value propagate” filter options

Presets, “Input Type”, Clipping, Blending Options, Preview, Split view

[注意]注意

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

Mode

The examples will be about the following image:

5.13. Value Propagate - 图5

  • More white (larger value)

    Pixels will be propagated from upper value pixels towards lower value pixels. So bright areas will enlarge.

    图 17.86. More white

    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.

  1. More black (smaller value)
  3. Pixels will be propagated from lower value pixels towards upper value pixels. So dark areas will enlarge.
  5. **图 17.87. More black**
  7. ![More black](/projects/gimp-2.10-zh/39238978db9a89ddeb10f9d893b34e80.png)
  10. **图 17.88. To bottom only**
  12. ![To bottom only](/projects/gimp-2.10-zh/9472f66b6afaff69a95d37ab99afeccb.png)
  14. The same as above with To bottom direction only checked.
  17. Middle value to peaks
  19. On a border between the selected thresholds, the average of both values is propagated.
  21. **图 17.89. Middle value to peaks**
  23. ![Middle value to peaks](/projects/gimp-2.10-zh/f1339c521c1a2e9a7430437ff6c84ef5.png)
  25. A thin border with a transitional color has been added to objects. It is not visible around objects with smoothed borders.
  27. ![Middle value to peaks](/projects/gimp-2.10-zh/3d257983c7b20ee5e412730a894da17b.png)
  29. Green area zoomed x800. A thin border (one pixel wide) has been added. Its value is the average between gray (90%) and green (78%) : (90 + 78) / 2 = 84.
  32. Color to peaks
  34. The propagated areas will be filled with the foreground color of the toolbox.
  36. A color selector opens, with a color picker.
  38. **图 17.90. Color to peaks**
  40. ![Color to peaks](/projects/gimp-2.10-zh/a51eb477bed8b6aca930ff815b1bc9ed.png)
  42. In this example, the selected color 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 artifact due to the small size of the object which makes the smoothing area of opposite sides to overlap.
  45. Only color
  47. Only areas with the selected color will propagate. With this option, soft and fuzzy edges don't propagate well.
  49. **图 17.91. Only color**
  51. ![Only color](/projects/gimp-2.10-zh/3963f093f88e83f5df43100248c78563.png)
  53. In this example, the selected color is that of the green object. After applying filter several times, the green area is clearly enlarged.
  56. More opaque, More transparent
  58. 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.
  60. **图 17.92. More opaque**
  62. ![More opaque](/projects/gimp-2.10-zh/9d18cd041d34514d74ca927f920e8f44.png)
  64. Original layer, with a transparent background.
  66. ![More opaque](/projects/gimp-2.10-zh/5b60b0c9743a4113a2e56d5ee8e085f3.png)
  68. Filter applied several times: the green, opaque, area got increased.

Lower threshold, Upper threshold

A pixel will be propagated (spread) if the difference in value between the pixel and its neighbor is no smaller than the lower threshold and no larger than the upper threshold.

Propagating rate

That’s the propagating amount. The higher it will be the more colored the propagation will be.

To top, To left, To right, To bottom

You can select one or more directions.

Propagating value channel

If checked, the pixel’s color channels (gray channel on grayscaled images) will be propagated. The option is checked by default, of course.

Propagating alpha channel

If checked, the pixel alpha value will be propagated, otherwise the pixel will get the alpha of the neighboring pixels.

5.13.4. Using Value Propagate

5.13. Value Propagate - 图7

Left: Original……..Middle: More white……..Right: More black