Selective Coloring with a Perceptual Color Distance 

Selective desaturation is an effect commonly used to highlight specific details or objects in an image.

Create a distance map between pixels of an image and a given color using ColorDistance with a perceptually accurate distance function such as the CIE2000 color difference.

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Use the map as a mask to highlight the regions close to the target color.

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Compose the original image and its grayscale version using the distance map.

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