Figure 6-3.6
A normal linear contrast stretch compared to a piecewise linear contrast stretch. The white histogram is the histogram of the raw data values before any enhancement is applied. The red, green, and blue plots are the histograms of the displayed image after the linear stretch is applied. In the normal linear contrast stretch example, the minimum and maximum values are stretched to the values of 0 and 255 at a constant level of intenstity (defined by the black line). In the piecewise linear contrast stretch, several breakpoints are defined that increase or decrease the contrast of the image for a given range of values. The higher the slope, the narrower the range of values being input from the x-axis. This results in a wider output spread for those same values and thus, increases the contrast for that range of values. A low sloping line results in a lower contrast for the same range of values.

Back to Linear Contrast Enhancement