Patent ID: 7885462

Claim:
An image processing method comprising: obtaining a brightness histogram; computing a mean brightness of an input image; determining a clipping rate based on the computed mean brightness; determining a clipping threshold based on the determined clipping rate; obtaining a clipped brightness histogram by clipping frequencies exceeding the determined clipping threshold in the obtained brightness histogram; obtaining a corrected brightness histogram b correcting the clipped brightness histogram using the clipping rate as a total gain; obtaining a cumulative histogram from the corrected brightness histogram; and correcting the input image using the cumulative histogram as a transformation function, wherein the step of obtaining the corrected brightness histogram comprises: determining a global gain and a local gain based on the total gain; and obtaining the corrected brightness histogram using the global gain and the local gain, wherein the global gain is uniformly distributed throughout the clipped histogram, and the local gain is distributed to a particular region of the clipped histogram, and wherein a sum of the global gain and the local gain is the same as the clipping rate; wherein the step of determining the global gain and the local gain comprises determining a first local gain for a first region and a second local gain for a second region based on the determined local gain; wherein the step of obtaining the corrected brightness histogram using the global gain and the local. gain comprises: determining the first region and the second region in the clipped brightness histogram; correcting the first region of the clipped brightness histogram using the first local gain; and correcting the second region of the clipped brightness histogram using the second local gain; wherein the step of determining the first local gain and the second local gain is performed using: Local _Gain _Low=(Total _Gain-Global _Gain)/2 Local _Gain _High=(Total _Gain-Global _Gain)/2 where Total_Gain, Global_Gain, Local_Gain_Low, and Local_Gain_High denote the total gain, the global gain, the first local gain, and the second local gain, respectively.