Comparison of Global ? Local Contrast Enhancement in Image Processing

ABSTRACT Enhancement is the modification of an image to alter impact on the viewer. Generally enhancement distorts the original digital values; therefore enhancement is not done until the restoration processes are complete. Contrast enhancement is a strong influence of contrast ratio on resolving power and detection capability of images. Techniques for improving image contrast are among the most widely used enhancement processes. Using global contrast enhancement, low contrast image can be improved in its quality globally. The enhanced output image, with such type of enhancement, may not have the noise and ringing artifacts. Local contrast enhancement attempts to increase the appearance of large-scale light-dark transitions, similar to how sharpening with an "Unsharp mask" increases the appearance of small-scale edges.