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| Architecture with centralized single memory for the transfer of video images |
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| White balance controller for an image pick-up apparatus including an abnormality detector |
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| Method and apparatus for three-dimensional testing of printed circuitboards |
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| Method for shape detection and apparatus therefor |
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| Method for inspecting solder paste in printed circuit board manufacture |
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Method of improving a digital image as a function of its dynamic range
| Details |
Inventors: Woodell, Glenn A.; Jobson, Daniel J.; Rahman, Zia-ur;
Assignee: Science and Technology Corp. (Hampton, VA); The United States of America as represented by the Administrator of the (Washington, DC)
Primary Examiner: Couso; Von J.
Assistant Examiner: Chawan; Sheela
Attorney, Agent or Firm: Van Bergen; Peter J.
The present invention is a method of processing a digital image that is initially represented by digital data indexed to represent positions on a display. The digital data is indicative of an intensity value I.sub.i (x,y) for each position (x,y) in each i-th spectral band. A classification of the image based on its dynamic range is then defined in each of the image's S spectral bands. The intensity value for each position in each i-th spectral band is adjusted to generate an adjusted intensity value for each position in each i-th spectral band in accordance with ##EQU1## where W.sub.n is a weighting factor, "*" is the convolution operator and S is the total number of unique spectral bands. For each n, the function F.sub.n (x,y) is a unique surround function applied to each position (x,y) and N is the total number of unique surround functions. Each unique surround function is scaled to improve some aspect of the digital image, e.g., dynamic range compression, color constancy, and lightness rendition. The adjusted intensity value for each position in each i-th spectral band of the image is then filtered with a filter function that is based on the dynamic range classification of the image. |
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DETAILED DESCRIPTION Accordingly, it is an object of the present invention to provide a method of improving an image created with digital data for both color and non-color images.
Another object of the present invention to provide a method of improving a digital image in terms of the image's dynamic range compression, color independence from the spectral distribution of the scene illuminant, and color/lightness rendition.
Still another object of the present invention to provide a method of improving a digital image so that the image appears similar to what is perceived by human vision in all kinds and levels of lighting across the entire scene.
Yet another object of the present invention is to provide a method of improving a digital image regardless of the image's dynamic range.
A further object of the present invention is to provide a method of reducing the "graying" of large white zones in a processed digital image.
Other objects and advantages of the present invention will become more obvious hereinafter in the specification and drawings.
In accordance with the present invention, a method of processing a digital image is provided.
The image is initially represented by digital data indexed to represent positions on a display.
The digital data is indicative of an intensity value I.
sub.
i (x,y) for each position (x,y) in each i-th spectral band.
A classification of the image based on its dynamic range is then defined in each of the image's spectral bands.
The intensity value for each position in each i-th spectral band is adjusted to generate an adjusted intensity value for each position in each i-th spectral band in accordance with ##EQU3## where W.
sub.
n is a weighting factor, "*" is the convolution operator and S is the total number of unique spectral bands.
For each n, the function F.
sub.
n (x,y) is a unique surround function applied to each position (x,y) and N is the total number of unique surround functions.
Each unique surround function is scaled to improve some aspect of the digital image, e
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Image Analysis 
