Various techniques are disclosed to generate a contrast-enhanced combined image based on a thermal image and high spatial frequency content extracted from a visual light image, said images depicting the same scene. In one example, a method comprises: determining a blending measure indicating the quality of at least one of said images; combining luminance components of pixel values comprised in the thermal image and of pixel values representing high spatial frequency content comprised in the visual light image based on the blending measure; and generating a contrast-enhanced combined image based on the thermal image and the combined luminance components.