The present invention relates to methods and apparatus for quantizing a bin value of a histogram. A method according to the present invention can include dividing a bin value into N+1 regions using N threshold values; and dividing and quantizing each respective one of the divided regions uniformly and with greater resolution to yield smaller divisions as a region is nearer to zero. For example, the bin value can be divided into six regions using five non-uniform threshold values (th1, th2, th3, th4 and th5), which can be set to 0.000000001, 0.037, 0.08, 0.195, and 0.32, respectively. A first region (