Patent ID: 9225943
Filing Date: 2015-12-29
Classification: G01N,G06T,H04N

Abstract:
1. A method to detect PTZ video image visibility based on luminance features of an image, with the characteristics of using PTZ video cameras to obtain road condition video images, to extract the road surface domain of interest (ROI), and to achieve the selected pixel height consistency; using region-growing algorithm based on Nagao filter to obtain accurate road surface area, removing interference from the roadbed and vehicles, ensuring consistent illumination of selected image pixels in world coordinates; extracting contrast curve reflecting road surface brightness variation within the road surface area, identifying feature points of the brightness curve, and calculating the farthest image pixel distinguishable to human eye through the use of extinction coefficient; and calculating the maximum visibility distance in combination with the camera calibration, and determining visibility value, comprising the following steps: 1) collecting real-time road condition video images through existing PTZ video cameras; 2) determining the conversion relationship between the images and their corresponding world coordinates of the road surface through the camera calibration technology, after processing the video images from the video cameras, and calculating the distance of the road surface [ ] area of the video images and camera; 3) using Kluge model fit lane division lines to the projections of the video images, through the unknown parameters from randomly solved Hough model, designating the area between the lane division lines as current region of interest (ROI); limiting subsequent image processing to the ROI to ensure the consistency of image pixel height; 4) using region-growing algorithm, combined with ROI brightness criteria and adaptive Nagao filtering method, extracting road mask area accurately and focusing all subsequent processing on the mask area to reduce the number of calculations and to ensure consistent brightness of the selected pixels within the world coordinates; 5) extracting a brightness feature, including: identifying feature point of change, which is also the zero point for the second derivative of the luminance curve; 6) calculating visibility, including: