The goal of image enhancement is to alter an image to highlight visual differences. Our eyes are not great at detecting variations in gray tones. Once colors are added, our eye easily identifies patterns. Image enhancement also helps in digital classification routines by altering brightness values to emphasize certain brightness ranges. Enhancement processes includes contrast stretching, composite generation, and digital filtering.
Composite generation adds colors to the different bands to enhance differences in brightness values.
The resulting color of the image would be a combination of RGB colors. We are limiting ourselves to 3 colors and therefore 3 bands. As a matter of convention the shorter wavelengths are included in the blue layer and the longer wavelengths in the red layer. Although this approach is, technically speaking, image transformation, the intent of the method is to mimic a true RGB color composite and is therefore included within the enhancement subcategory of digital processing. The original set of bands must be reduced and combined into a single composite.