In one embodiment, a light sensor, such as a camera, records an image through the surface with the residue to produce a stained image. A processor associated with the camera identifies object outlines within the image using a machine learning model, and smooth the colors within the object outlines. In another embodiment, the light sensor is placed beneath a dual-mode region of a display containing the residue. The dual-mode region can be opaque and function as part of the display, or can be transparent and allow environment light to reach the light sensor. Initially, the processor determines the position of the residue by causing the dual-mode region to display a predetermined pattern, while the light sensor records the predetermined pattern. Using the determined position of the residue, the processor corrects the pixels within the residue in the recorded image, by interpolating the values of the pixels outside of the residue.