The Sponge Brush Tool can be used to selectively saturate or desaturate areas within an image.
The following settings can be adjusted from the context toolbar:
Width—the brush (stroke) size in pixels. Type directly in the text box or drag the pop-up slider to set the value.
Opacity—how see through the brush is. Type directly in the text box or drag the pop-up slider to set the value.
Flow—how fast the brush effect is applied (1% is very slow, 100% is immediate). Type directly in the text box or drag the pop-up slider to set the value.
Hardness—how hard the edges of the brush are. The brush appears softer as the percentage decreases. Type directly in the text box or drag the pop-up slider to set the value.
More—click to display the Brushes dialog to access advanced brush settings.
Stabiliser—enables stroke stabilisation using either a Rope stabiliser or Window stabiliser mode; the former drags the stroke end by a 'rope' to smooth the stroke but lets you introduce sharp corners at increasing rope Length (radius) values by redirecting the slackened rope; the latter will smooth the stroke by averaging sampled input positions within a Window whose size is configurable.
Force pressure to control size—Click to control brush size with pressure if using a pressure-sensitive device. This overrides brush defaults.
Saturate—when selected, brush strokes increase the saturation of the existing pixels.
Desaturate—when selected, brush strokes decrease the saturation of the existing pixels.
Vibrance—when selected, brush strokes adjust the intensity of subtle coloured pixels, while minimizing clipping of highly saturated coloured pixels.
Saturation—when selected, adjusts the colour intensity of all pixels.