Patent ID: 8285071

Claim:
A digital image content-adaptive contrast improving method, comprising the steps of: generating a histogram recording luminance distribution of a digital image; sectionalizing pixels of said digital image into a plurality of pixel groups, said pixel groups respectively covering pixels lying in exclusive luminance ranges; forming a piecewise linear tone remapping function for said digital image according to said histogram, said piecewise linear tone remapping function being represented by a plurality of line segments consecutively connected to each other one by one, each of said line segments representing a local linear remapping function for one of said pixel groups, comprising: a first step for determining a starting linear tone mapping function for a specific range of luminance values, which is between a first code value C1 and a second code value C2 greater than said first code value C1, said specific range of luminance values covering luminance values of at least two said pixel groups; and applying said piecewise linear tone remapping function to said digital image; wherein, said piecewise linear tone remapping function is formed by repeatedly performing said first step and a second step, wherein said specific range and said starting linear tone mapping function are different in each instance of said first and second steps.