Method for reducing shadows and/or noise in a digital image

Details Method for reducing shadows and/or noise in a digital image Method for reducing shadows and/or noise in a digital image

1999-07-02

2003-12-30

Lee, Thomas D. (Department: 2624)

Image analysis

Image enhancement or restoration

Intensity, brightness, contrast, or shading correction

C382S275000, C382S174000, C358S463000, C358S464000

Reexamination Certificate

active

06671419

ABSTRACT:

BACKGROUND
1. Field
This disclosure relates to processing digital images and, more particularly, to reducing shadows in a digital image.
2. Background Information
In digital imaging systems, a variety of forms of digital image processing operations are performed. Frequently, the processing applied depends on the particular application. Nonetheless, one difficulty in digital image processing is dealing with shadows that may be cast by an object appearing in the digital image. Again, this depends somewhat on the particular application, however, in a variety of applications, shadows may become problematic. For example, where digital images are employed in automated target acquisition and tracking, surveillance applications, or navigation applications performed automatically by a navigational platform, the shadows may result in errors in tracking and/or navigation. Likewise, where digital images are interpreted, such as by a computer or similar computationally intensive processing apparatus or device, such shadows may result in errors in interpretation. For example, where gestures are to be interpreted, shadows may result in errors in the interpretation of the gesture. There are many other possible examples in which shadows in a digital image are not desirable. A need, therefore, exists for a method or technique of addressing, through digital image processing, shadows that may appear in a digital image.
SUMMARY
Briefly, in accordance with one embodiment of the invention, a method of reducing shadows and/or noise in a digital image includes the following. A noise floor for the digital image is estimated. A threshold level for a difference image of the digital image and a background image is determined based, at least in part, on the noise floor estimate. The digital image is modified based, at least in part, on the determined threshold level and the difference image.


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