Vips::Enums::Signal

Evaluation is starting The preeval signal is emitted once before computation of Image starts. It's a good place to set up evaluation feedback.

The eval signal is emitted once per work unit (typically a 128 x 128 are of pixels) during image computation

You can use this signal to update user-interfaces with progress feedback. Beware of updating too frequently: you will usually need some throttling mechanism

Ealuation is ending The posteval signal is emitted once at the end of the computation of Image. It's a good place to shut down evaluation feedback.

Returns true if this enum value equals Eval

Returns true if this enum value equals PostEval

Returns true if this enum value equals PreEval