Method and apparatus for pixel level luminance adjustment

Details Method and apparatus for pixel level luminance adjustment Method and apparatus for pixel level luminance adjustment

1996-03-14

1999-02-09

Lee, Thomas D.

Image analysis

Image enhancement or restoration

Intensity, brightness, contrast, or shading correction

382272, 358448, 358447, 358465, G06K 938, G06K 940, H04N 140

Patent

active

058705058

ABSTRACT:
A method for adjusting the luminance IM.sub.HI of pixels in a high resolution image includes first forming a low resolution image of the original by grouping pixels into superpixels such as 8.times.8 blocks. A low resolution luminance correction value .delta..sub.LO is determined for each superpixel by comparing the luminance of the superpixel to both a predetermined darkness threshold T.sub.D and a predetermined brightness threshold T.sub.B. The low resolution luminance correction value .delta..sub.LO is modified to yield .delta.'.sub.LO for each superpixel by forming islands of the superpixels and smoothing .delta..sub.LO between superpixels within each island. Finally, a high resolution luminance correction value .delta..sub.HI is calculated for each pixel of the original high resolution image by comparing the luminance IM.sub.HI of each pixel to both T.sub.D and T.sub.B, keeping in mind that .delta..sub.HI is generated through a series of mathematical computations as a function of both the pixel luminance IM.sub.HI and the low resolution luminance correction value .delta..sub.LO. Each pixel of the original image is adjusted by the corresponding high resolution luminance correction value .delta..sub.HI and a luminance adjusted image is produced.

REFERENCES:
patent: 4703363 (1987-10-01), Kitamura
patent: 4747156 (1988-05-01), Wahl
patent: 4841374 (1989-06-01), Kotani et al.
patent: 4903316 (1990-02-01), Hongo et al.
patent: 4999629 (1991-03-01), Katsuta
patent: 5235434 (1993-08-01), Wober
U.S. Patent Application No. 08/414,750 filed Mar. 31, 1995 by Boyack & Juenger.

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