Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for generating, based on a portrait image, a foreground image mask to indicate foreground pixels of the portrait image; identifying a percentage of white or near white pixels in the foreground by using the foreground image mask and pixel colors in the portrait image; determining whether the percentage of white or near white pixels in the foreground is larger than a predefined threshold; in response to determining, triggering identification of edge pixels in a background of the portrait image; adjusting white background pixels to add shadows by darkening the white background pixels; and adjusting the white or near white pixels in the foreground by darkening the white or near white pixels.