The Desaturate component converts the image provided by the Source input into grayscale according to the specified Method. This operation affects only the color of the source image, it does not affect its alpha channel. This is a map component, it can be located in the Adjustments category on the Components Bar. This component can output HDR colors.
Source: Map Input (HDR), Required
Provides the source image to be desaturated. This is a required input – in order to make the Desaturate component work, this input must be connected. This input can accept HDR colors.
Specifies the desaturation method. The following methods are available:
- Weighted Average – based on the HSY color model, taking the Y channel as a grayscale value. This method is recommended when you need to take human perception of color into account, for example, when converting color photos into black-and-white.
- Average – produces a grayscale value by averaging R, G, and B channels. This method is non-perceptual and is best for 'technical' conversion of color into grayscale. For example, this method is used by Filter Forge for automatic conversion of color data in grayscale map inputs.
- Lightness – based on the HSB color model, taking the B channel as a grayscale value. This method is provided for compatibility with Adobe® Photoshop® which uses this method in its 'Desaturate' adjustment. For more information on the HSB (HSV) color model, see this Wikipedia article.
When a map component is connected to this input, the number of the selected list item is determined separately for different image areas by the HDR brightness level of the image supplied by that component. The item number is calculated as the brightness level rounded to the nearest integer: the brightness level of 0 to 0.5 corresponds to the first item, the level of 0.5 to 1.5 to the second item, and 1.5 to 2.5 to the third item. Out-of-range values are clipped, which corresponds to the last item of the list.
