The invention relates generally to edge detection and presentation in thermal images. Infrared and visible light images comprising at least partially overlapping target scenes are analyzed. An edge detection process is performed on the visible light image to determine which pixels represent edges in the target scene. A display image is generated in which some pixels include infrared image data and in which pixels corresponding to edges in the visible light image include a predetermined color and do not include corresponding infrared image data to emphasize edges. Edge pixels in the display image can include exclusively the predetermined color, or in some examples, a blend of a predetermined color and visible light image data. Methods can include replacing one or the other of visible light edge pixels or corresponding infrared pixels with the predetermined color before combining the visible light and infrared image data to create a display image.