Saturation

This transformation lets you adjust the overall color saturation of an image.

Amount

The amount control lets you control how much and in what direction the saturation of the image is changed. Positive values make the image more saturated; negative values make the image less saturated. You can apply the transformation to the entire image, making it more or less saturated, or you can specify an amount mask to saturate or desaturate different parts of the input image by different amounts. When you use an amount mask, the input image is left unchanged where the mask image is a mid-level gray; it is made more saturated where the mask is brighter and desaturated where the mask is darker. You can control the degree of saturation change caused by the mask image using the double slider.

Color Space

If the input image is color then this control lets you select whether you want to work in the HSV or HSL color space. Using HSL, saturation changes are more pronounced in the mid-tones; using HSV, saturation changes are more pronounced in the highlights.

Preserve

There are many ways to saturate or desaturate an image. This control lets you select what parts of the saturation scale of the input image are most affected and what parts of the scale remain unchanged.

Low -- saturates or desaturates the input image by applying a curve that keeps unsaturated areas unsaturated and has its strongest effect on the most saturated areas.

High -- saturates or desaturates the input image by applying a curve that keeps saturated areas saturated and has its strongest effect on the least saturated areas.

This setting should normally be avoided, since it exaggerates color in neutral areas of the input image that contain little or no color information to begin with. By arbitrary convention the hue of a perfectly neutral gray is zero which corresponds to red. Increasing the saturation of a neutral gray region therefore makes it red.

Low and High -- saturates or desaturates the input image by applying a curve that keeps unsaturated areas unsaturated and fully saturated areas fully saturated and has its strongest effect on the regions of mid-level saturation.

Neither -- saturates or desaturates the input image by applying a curve that adds or subtracts the same amount to the entire saturation scale, affecting all levels equally. This setting should normally be avoided (see above).