Pixel Operation: An Introduction

Pixel operation is operation of an image where each pixel's intensity value is modified. The modification/transformation depends solely on it's previous value, regardless of its position and other pixels value. Some image operation in this category are brightness modification, contrast enhancement, color inversion (negation), and thresholding operation.

Pixel operation is done by transforming each pixel value to new value according to a transformation function, known as gray-scale transformation (GST) function. This function map the gray-level input (Ki) to an new gray-level output (Ko). In general, a GST function can be expressed as:

Ko=f(Ki)

Figure 1. typical Gray-Scale Transformation (GST) Function Plot

The mapping of typical GST function can presented as transformation curve, as shown in Figure 1. The function can be linear or non-linear. In a true color image, GST function is applied to each RGB elements. Each function for each color element can take the same form or different depends on the application.