Patent ID: 7336849

Claim:
An exposure correction method for a digital image comprising: converting the image into a gray-level image and computing the gray-level histogram thereof; determining whether the exposure of the image is normal from the gray-level histogram, thereby determining an exposure threshold, Ratio-Threshold; extracting a central region of the image and computing the average brightness, Iave, of the pixels in the central region; computing a destination brightness, Idest, according to the average brightness and using Iave and Idest to determine an adjusting curve y=f(x); construting a lookup table according to the adjusting curve y=f(x); and converting the image into a HSI (Hue, Saturation, Lightness) format; wherein the adjusting curve f(x) has the expression: f ( x )= k *ln( a*x+ 1) when I ave< I dest; and f ( x )= k*e ( a*x )− k when I ave> I dest.