Teachings herein compose a digital image so that the image is perceptible on a viewing surface, such as a projection surface or a transparent screen. In doing so, the teachings advantageously recognize a digital image as consisting of one or more logical objects, like buttons of a user interface. Often, logical objects may be spatially arranged within the image and/or colored in different possible ways without substantially affecting the meaning conveyed by the image. Exploiting this, teachings herein evaluate light reflected from, or transmitted through, the viewing surface, and compose the digital image from one or more logical objects that have a spatial arrangement or coloration determined in dependence on that evaluation. The teachings might, for example, place a logical object within the image so that it will be displayed on a region of the surface which has high contrast with the object's colors and/or low color variance.