1. A method, comprising: determining, for a pixel in a first image, that the pixel is: an opaque pixel when the luma value of the pixel is within an opaque range that is greater than or equal to a minimum value and less than a first predetermined value, a transparent pixel when the luma value of the pixel is within a transparent range that is less than or equal to a maximum value and greater than a second predetermined value, an intermediate pixel when the luma value of the pixel is within an intermediate range that is greater than the first predetermined value and less than the second predetermined value, wherein the first image is one of an overlay image and a main image, each pixel of the main and overlay images being defined by a luma component and at least one color component, and each luma component taking a value within a luma range, the lowest and highest values in the luma range being, respectively, the minimum value and the maximum value; and replacing each pixel of a second image that is in a location that corresponds to the location of an opaque pixel in the first image with the corresponding opaque pixel of the first image, wherein the second image is the other of the overlay image and a main image.