Contrast in an image is enhanced by mapping an input intensity value to an output intensity value in accordance with a mapping function. A mean intensity value of the image is determined. Co-ordinates of the mapping function are calculated in accordance with the mean intensity value and a plurality of predefined parameters. The mapping function is applied to the input intensity value for determining the output intensity, wherein the mapping function is generated dynamically for each image.
The contrast of a digital image is enhanced by forming a histogram of the luma values of an active area of the image, computing "initial" bin indices that partition the histogram into bins of substantially equal population, mapping the "initial" bin indices into "final" bin indices that are more uniformly spaced than the "initial" bin indices, and adjusting the luma values of all the pixels in accordance with the "final" bin indices.
Disclosed is a method for generating transfer curves for adaptive contrast enhancement. Transfer curves are generated so as to enhance the bright pixels in mostly dark images and the dark pixels in mostly bright images. For a dark image, a transfer curve is generated which increases luminance in high-luminance regions of the image without substantially changing the luminance in the mid- and low-luminance regions of the image. For a bright image, a transfer curve is generated which decreases the luminance in the dark areas of the image without substantially changing the luminance in the mid- and high-luminance regions of the image. For a medium-bright image, a transfer curve is generated with increases the luminance in the high-luminance range and decreases the luminance in the low-luminance range of the histogram without substantially changing the luminance in the medium-luminance range of the image.
