Patent ID: 7356201

Claim:
A process for automatic rectification of images, wherein an image is rectified by a mapping function onto a reference image, and at least some parameters of the mapping function are unknown, said process comprising: extracting at least three objects from the image; determining at least three control points in the image, such that characteristic object points of the extracted objects are determined as control points; obtaining positions of the at least three control points in the image, and comparing control point structures in the image to be rectified to control point structures in the reference image, each of the control point structures comprising a plurality of pixels; calculating a resolution of the image and the reference image for an image area to determine which image area is less-resolved and which image area is more highly resolved, said image area of the image to be rectified comprising a control point structure and said image area of the reference image comprising a control point structure corresponding to the control point structure in the image to be rectified; projecting the less-resolved image area onto the more highly resolved image area corresponding to at least one suitable mapping function; determining gray-scale values of respective pixels in the control point structure of the image and in the corresponding control point structure of the reference image; forming differences of gray-scale values between adjacent pixels in the control point structure of the image and forming differences of gray-scale values between adjacent pixels in the corresponding control point structure of the reference image; comparing said differences in the corresponding control point structures between adjacent pixels in the control point structure of the image with said differences of gray-scale values of adjacent pixels in the corresponding control point structure of the reference image to derive an error value; shifting the control point structure in the image in at least one of a vertical and horizontal direction such that a new position of the control point structure is obtained, said error value being determined by comparing said differences in the corresponding new control point structure between adjacent pixels in the new control point structure of the image with said differences of gray-scale values of adjacent pixels of the corresponding new control point structure of the reference image; assigning the at least three objects to objects in the reference image, such that assignment is made according to at least one of similarity between corresponding objects in the two images and based on a vector grid formed by connections between the characteristic object points; and selecting one of a suitable mapping function and adjusting parameters of the mapping function based on the error values, whereby the mapping function is changed by changing the parameters such that cumulative error in positional differences between control points and corresponding points in the reference image is minimized.