7.40. Soglia alfa

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. 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. Attivazione del comando

You can access this command

  • From the main menu through LayerTransparencyThreshold Alpha….

7.40.2. Descrizione della finestra di dialogo

Figura 16.103.  The «Threshold Alpha» filter options dialog

The «Threshold Alpha» filter options dialog

Presets, Input Type, Blending Options, Preview, Split view
[Nota] Nota

Queste opzioni sono descritte in Sezione 2, «Caratteristiche comuni».


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.

[Nota] Nota

Questo comando non renderà mai i pixel completamente trasparenti (valore alfa = 0) opachi.

Figura 16.104. Esempio di soglia alfa

Esempio di soglia alfa
Un gradiente trasparenza 0-255.
Esempio di soglia alfa
Soglia impostata a 50, 127, 210.