### 7.40. Seuil alpha

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.

| Note
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. Accès à la commande

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

#### 7.40.2. Description de la fenêtre de dialogue

Figure 16.100. The « Threshold Alpha » filter options dialog

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

  | Note
  Ces options sont décrites dans Section 2, « Options communes ».

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.

  | Note
  Cette commande ne rendra jamais complètement transparents (valeur Alpha = 0) les pixels opaques.

  Figure 16.101. Exemple de Seuil alpha

  Un dégradé de transparence 0-255
  Seuil alpha fixé à 50, 127, 210

7.39. Semi-Flatten |  | 7.41. Alpha vers sélection

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