9.6. 明るさの最大値
| 9. 汎用フィルター |

### 9.6. 明るさの最大値

#### 9.6.1. 概観

図17.191 Applying example for the Erode filter

元画像

Filter 「Erode」 applied

明るさの最小値 フィルターは活性レイヤーもしくはその選択範囲の暗い部分を拡げ、 強調します。

For every image pixel, it brings the pixel Value (luminosity) into line with the lowest Value (the darkest) of the 8 neighboring pixels (3×3 matrix). So, a dark pixel is added around dark areas. An isolated pixel on a brighter background will be changed to a big 「pixel」, composed of 9 pixels, and that will create some noise in the image.

In this image, the studied pixel has a red border and the studied 3×3 matrix has a green border. Thus when the pixel marked with 「I」 is inside the green border, the studied pixel turns to black.

A larger dark area will expand by one pixel in all directions:

フィルターを 3 回繰り返し適用しました。

On more complex images, dark areas are widened and enhanced the same, and somewhat pixelated. Here, the filter was applied 3 times:

もちろん背景がその上に描かれたものよりも暗ければ、 やがて背景色が画像全体を覆うことになるでしょう。

#### 9.6.2. Activating the Filter

This filter is found in the main menu under Filters → Generic → Erode.

#### 9.6.3. 使用例

図17.192 Erode text

9.5. 明るさの最小値 |  | 9.7. GEGL Graph

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