Digital photos are represented as a two-dimensional grid of "pixels" (short for picture elements). Associated with each pixel are two pieces of information − its position in the photo and its color. The position of a pixel is its horizontal and vertical distance from the top-left corner of the image. For example, in Figure 2, a pixel with position (56, 60) is the 56th pixel counting from left to right and the 60th pixel counting from top to bottom.
Figure 3: Color mixer
Our eyes can perceive millions of colors. Remarkably, most of these colors can be produced by mixing just three primary colors of light − red, green and blue − in varying proportions [1]. Therefore, the color of a pixel is typically represented using three numbers – the brightnesses of the three primary colors. The interactive demo in Figure 3 shows how red, green and blue can be mixed to generate virtually all the colors we experience. Use the sliders to control the amount of each primary color. You can read more about pixels and color in Image Sensor.
H. Helmholtz, Physiological Optics − The Sensations of Vision, 1866, as translated in D. L. MacAdam, Sources of Color Science, Cambridge MIT Press, 1970.
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