Anatomy of an Image

Digital images are made of pixels. A pixel is the single smallest unit of an image. Images have rows and columns of pixels; the number of columns by the number of rows is said to be the image's resolution. The more pixels an image has, the more faithful a representation can be made. Then too, the more pixels an image has, the more processing is required to analyze it, which can slow down your program. In general, for image processing, it is ideal to keep the image as small as possible while maintaining the desired fidelity. Figure 4-1 shows some different resolution examples.

Figure 4-1. Icons (left) can be as small as 8 × 8 pixels (64 total pixels). A 1024 × 728 resolution image (right) has 745,472 pixels. The Kinect RGB and depth cameras (center) are both 640 × 480 (307,200 pixels).