Method and apparatus for determining ambient conditions from an image sequence, such as fog, haze or shadows
First Claim
Patent Images
1. A method for detecting ambient conditions of a scene represented by a sequence of images comprising the steps of:
- generating a reference image containing background information regarding the scene;
comparing, pixel-by-pixel, each of said images in said sequence of images to said reference image;
classifying, in response to each comparison, the pixels of said images as either background or non-background;
comparing a brightness measure of each non-background pixel, computed over a neighborhood of pixels local to that pixel, against a threshold; and
processing each non-background pixel to determine the ambient conditions of the scene byclassifying, in response to said comparison, each of said non-background pixels as either bright or dark;
comparing an energy value of each pixel in said image to an energy value in each pixel of said reference image;
determining a mean energy difference of all bright non-background pixels and a mean energy difference for all dark non-background pixels; and
processing the mean energy difference of the dark and bright pixels to determine if the scene contains shadows.
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Abstract
A method and apparatus for determining certain ambient conditions in a scene by analyzing a sequence of images that represent the scene. The apparatus uses only image information to determine scene illumination, or the presence of shadows, fog, smoke, or haze by comparing properties of detected objects, averaged over a finite video sequence, against properties of the reference image of the scene as that scene would appear without any objects present. Such a reference image is constructed in a manner similar to time-averaging successive camera images.
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Citations
20 Claims
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1. A method for detecting ambient conditions of a scene represented by a sequence of images comprising the steps of:
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generating a reference image containing background information regarding the scene; comparing, pixel-by-pixel, each of said images in said sequence of images to said reference image; classifying, in response to each comparison, the pixels of said images as either background or non-background; comparing a brightness measure of each non-background pixel, computed over a neighborhood of pixels local to that pixel, against a threshold; and processing each non-background pixel to determine the ambient conditions of the scene by classifying, in response to said comparison, each of said non-background pixels as either bright or dark; comparing an energy value of each pixel in said image to an energy value in each pixel of said reference image; determining a mean energy difference of all bright non-background pixels and a mean energy difference for all dark non-background pixels; and processing the mean energy difference of the dark and bright pixels to determine if the scene contains shadows. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for detecting ambient conditions of a scene represented by a sequence of images comprising:
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a reference image generator for generating a reference image containing background information regarding the scene; a comparator for comparing, pixel-by-pixel, each of said images in said sequence of images to said reference image; an illumination processor for classifying, in response to each comparison, the pixels of said images as either background or non-background, for comparing a brightness measure of each non-background pixel, computed over a neighborhood of pixels local to that pixel, against a threshold, and for processing each non-background pixel to determine the ambient conditions of the scene, wherein said illumination processor comprises; a comparator for comparing an energy value of each pixel in said image to an energy value in each pixel of said reference image; means for determining a mean energy difference of all bright non-background pixels and a mean energy difference for all dark non-background pixels; and means for processing the mean energy difference of the dark and bright pixels to determine if the scene contains shadows. - View Dependent Claims (7, 8, 9, 10)
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11. A method for detecting ambient conditions of a scene represented by a sequence of images comprising the steps of:
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generating a reference image containing background information regarding the scene; comparing, pixel-by-pixel, each of said images in said sequence of images to said reference image; classifying, in response to each comparison, the pixels of said images as either background or non-background; comparing a brightness measure of each non-background pixel, computed over a neighborhood of pixels local to that pixel, against a threshold; and processing each non-background pixel to determine the ambient conditions of the scene by classifying, in response to said comparison, each of said non-background pixels as either bright or dark; comparing an energy value of each pixel in said image to an energy value in each pixel of said reference image; determining a mean energy difference of all bright non-background pixels and a mean energy difference for all dark non-background pixels; determining an absolute magnitude of the mean energy difference of all bright non-background pixels and an absolute magnitude of the mean energy difference for all dark non-background pixels; and processing the absolute magnitude of the mean energy difference of the dark and bright pixels to determine if the scene contains fog or haze. - View Dependent Claims (12, 13, 14, 15)
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16. Apparatus for detecting ambient conditions of a scene represented by a sequence of images comprising:
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a reference image generator for generating a reference image containing background information regarding the scene; a comparator for comparing, pixel-by-pixel, each of said images in said sequence of images to said reference image; an illumination processor for classifying, in response to each comparison, the pixels of said images as either background or non-background, for comparing a brightness measure of each non-background pixel, computed over a neighborhood of pixels local to that pixel, against a threshold, and for processing each non-background pixel to determine the ambient conditions of the scene, wherein said illumination processor further comprises; a comparator for comparing an energy value of each pixel in said image to an energy value in each pixel of said reference image; means for determining a mean energy difference of all bright non-background pixels and a mean energy difference for all dark non-background pixels; and means for processing the mean energy difference of the dark and bright pixels to determine if the scene contains fog or haze. - View Dependent Claims (17, 18, 19, 20)
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Specification