Patent ID: 7593591
Filing Date: 2009-09-22
Classification: G06K,G06T

Abstract:
1. A method of increasing contrast in a digital image comprising: determining an intensity distribution of pixels forming said digital image; identifying a low intensity pixel range in said distribution; adjusting intensities of pixels in said image wherein: during said adjusting, pixel intensities are stretched thereby to space pixels at different intensities apart; the low intensity pixel range includes a predominate number of the low intensity pixels in said image; during said adjusting, at least a portion of the pixels in said low intensity pixel range are re-scaled; during re-scaling, pixels having intensity values in a specified range are stretched towards a threshold value; when the threshold intensity value is above a designated value, pixels having intensities above said low intensity pixel region are re-scaled; the threshold intensity value is positioned such that 85% of the pixels in the low intensity pixel range have an intensity value that is less than the threshold intensity value; pixels forming said image have intensity values in the range of 0 to 255 and wherein said designated value is equal to 128; when the threshold intensity value is below the designated value, pixels in said low intensity pixel range are adjusted; and when the threshold intensity value is less than 64, pixels in the low intensity pixel range are stretched out either to between 128 to 160 or 96 to 128 depending on the upper pixel intensity value of the low intensity pixel range; and based on at least one feature of said low intensity pixel range, adjusting intensities of pixels in said image.