A Method for Enhancement of Image Contrasts by Arbitrarily Shaped Wavelet Transforms

In a method of contrast enhancement by arbitrarily shaped wavelet transform, a case that the level change in bounds is caused by the difference between the level of enhanced area and that of non-enhanced area is still observed. The objective of the present paper is to reduce that the extreme changes of level are caused by after operations of image contrast enhancement. This method applies pixel filling by mean levels of surrounding pixels to each pixel in non-enhanced area, instead of applying pixel filling by the same value to all pixels in the area. Simulation results demonstrate that this method reduces the surrounding mean gradients of non-enhanced area. It is also shown that the effects lead to reducing these gradients to less than four fifths in the maximum