### 7.40. Práh alfy

The Threshold Alpha… command converts semi-transparent areas of the active layer into completely transparent or completely opaque areas, based on a threshold you set.

| Poznámka
It only works on layers which have an alpha channel. If the Lock alpha channel option is checked in the Layers Dialog, the filter will have no effect. This command only works on a single layer.

#### 7.40.1. Activating the Command

You can access this command from the main menu through Layer → Transparency → Threshold Alpha….

#### 7.40.2. Volby

Obrázek 16.100. The „Threshold Alpha“ filter options dialog

Presets, Input Type, Blending Options, Preview, Merge filter, Split view

  | Poznámka
  These options are described in 2 – „Common Features“.

Value

  The threshold alpha value determines which values will become transparent or opaque. You can set the transparency value to be used by using the slider or by entering a value between 0 and 1 in the input box. All transparency values above this threshold will become opaque and all transparency values below or equal to this threshold will become completely transparent.

  | Poznámka
  This command will never make completely transparent pixels (alpha value = 0) opaque.

  Obrázek 16.101. Threshold Alpha example

  A transparency gradient 0-255.
  Threshold set to 50, 127, 210.

7.39. Semi-Flatten |  | 7.41. Alfa do výběru

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