Selecting objects or features within a scene or image is an important prerequisite for most kinds of measurement or analysis. Traditionally, one simple way this selection has been accomplished is to define a range of brightness values in the original image, select the pixels within this range as belonging to the foreground, and reject all of the other pixels to the background. Such an image is then usually displayed as a binary or two-level image, using black and white (or sometimes other colors) to distinguish the regions. There is no standard convention on whether the features of interest are white or black; the choice depends on the particular display hardware in use and the designer’s preference; in the examples shown here the features are black and the background is white, which matches most modern computer displays and printing that show black text on a white background.