Image processing apparatus and method for magnifying dynamic ran

Details Image processing apparatus and method for magnifying dynamic ran Image processing apparatus and method for magnifying dynamic ran

1998-11-23

2000-10-10

Hsia, Sherrie

Television

Image signal processing circuitry specific to television

Gray scale transformation

348672, 382169, 382172, H04N 552

Patent

active

061307246

ABSTRACT:
An apparatus and method for magnifying a dynamic range of an image while improving a contrast of an image are provided. A histogram calculator receives a digital image signal and calculates histograms depending on the illuminance distribution of an image. A histogram accumulator receives a histogram output by the histogram calculator, obtains an accumulative density function by integrating the input histogram up to each illuminance level and normalizes the accumulative density function, and generates an initial conversion function. A bias calculator determines a threshold value for dividing into a low illuminance level and a high illuminance level on the basis of a histogram output by the histogram calculator, and obtains a histogram compensation function for applying a negative bias to a histogram around the threshold value. A converter converts a digital image signal input with a predetermined delay time, according to an image conversion function obtained by applying the histogram compensation function to the initial conversion function. A digital-to-analog (D/A) converter converts a digital image signal converted by the converter into an analog image signal. Accordingly, the entire contrast of an image is improved, and simultaneously, the dynamic range thereof is magnified.

REFERENCES:
patent: 5144442 (1992-09-01), Ginosar, et al.
patent: 5294986 (1994-03-01), Tsuji
patent: 5959696 (1999-09-01), Hwang

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