1. A method, comprising: performing by a computer: determining a plurality of pixels of a background image according to a mask of a foreground image, wherein each background image pixel comprises a value in a non-luminance-isolating color space; for each of the plurality of pixels of the background image, converting the value in the non-luminance-isolating color space into a corresponding value in a luminance-isolating color space, wherein the value in the luminance-isolating color space comprises a luminance component; for each of the plurality of pixels of the background image, modifying the value in the luminance-isolating color space by altering the luminance component to create contrast between the foreground image pixels of the background image that surround the plurality of pixels of the background image; blurring at least some pixels that correspond to the plurality of pixels of the background image, wherein said blurring comprises adjusting pixel values of the some pixels that correspond to the plurality of pixels of the background image relative to pixel values for one or more adjacent pixels; for each of the plurality of pixels of the background image, converting the modified value in the luminance-isolating color space into a new value in the non-luminance-isolating color space; and blending the foreground image with the background image based on said blurring and on the new values.