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How is an image processed?
Most image processing algorithms (or operations) follow a simple procedure. For a given input image, the output image is computed one pixel at a time. The value at each pixel usually depends only on the value of the corresponding pixel in the input image or on a set of pixels within a small neighborhood (or window) around the corresponding pixel. In other words, the value is usually some mathematical combination of the pixel values within this neighborhood. The demo in Figure 4 shows the above process visually (Press the arrow button to play). The output image is computed one pixel at a time from left to right and top to bottom. In this example, the value of each pixel is computed over a small window of size 3 x 3 pixels centered on the corresponding pixel in the input image. In more complex image processing algorithms, the value may depend on pixels anywhere in the input image. In the following sections, we will see three common image processing operations.
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