Teachings herein prepare a digital image for display on a substantially transparent screen. The teachings advantageously recognize that the perceptibility of the digital image on the screen will often depend on what is visible to a user through the screen, since that will effectively serve as the background of the screen. A method of preparing a digital image thus includes dynamically calculating which part of an environmental background is visible to a user through the screen and thereby serves as an effective background of the screen. This calculation may entail obtaining an image of the environmental background and identifying which part of that image serves as the effective background (e.g., based on the angle at which the user views the screen). The method further includes composing the digital image for perceptibility as viewed against that effective background and outputting the composed image as digital data for display on the screen.