초록 ▼

A high precision sub-pixel spatial alignment of digital images, one from a reference video signal and another from a corresponding test video signal, uses an iterative process and incorporates spatial resampling along with basic correlation and estimation of fractional pixel shift. The corresponding

A high precision sub-pixel spatial alignment of digital images, one from a reference video signal and another from a corresponding test video signal, uses an iterative process and incorporates spatial resampling along with basic correlation and estimation of fractional pixel shift. The corresponding images from the reference and test video signals are captured and a test block is overlaid on them at the same locations to include texture from the images. FFTs are performed within the test block in each image, and the FFTs are cross-correlated to develop a peak value representing a shift position between the images. A curve is fitted to the peak and neighboring values to find the nearest integer pixel shift position. The test block is shifted in the test image by the integer pixel shift position, and the FFT in the test image is repeated and correlated with the FFT from the reference image. The curve fitting is repeated to obtain a fractional pixel shift position value that is combined with the integer pixel shift value to update the test block position again in the test image. The steps are repeated until an end condition is achieved, at which point the value of the pixel shift position for the test block in the test image relative to the reference image is used to align the two images with high precision sub-pixel accuracy.

대표청구항 ▼

1. A method of high precision sub-pixel spatial alignment of digital images comprising the steps of:capturing a reference image from a reference video signal as one of the digital images and a corresponding test image from a test video signal as another of the digital images, where the test video si

1. A method of high precision sub-pixel spatial alignment of digital images comprising the steps of:capturing a reference image from a reference video signal as one of the digital images and a corresponding test image from a test video signal as another of the digital images, where the test video signal represents the reference video signal after processing; overlaying an arbitrary test block on the reference and test images at corresponding locations that include texture; performing a fast Fourier transform for the portions of each image that lie within the test block to produce a reference FFT and a test FFT; cross-correlating the reference and test FFTs to produce a correlation surface having a peak correlation value, the position of the peak correlation value on the correlation surface being representative of a shift position between the reference and test images; fitting a curve to the peak and neighboring correlation values to determine an integer pixel shift position; updating the position of the test block overlaying the test image by the integer pixel shift position; and repeating the performing step for the test image, the correlating step for finding fractional pixel shift positions, and the updating step by adding the fractional pixel shift positions to the integer pixel shift position until an end condition is achieved, the final position of the test block in the test image from the updating step relative to the initial position of the test block in the test image providing the high precision sub-pixel shift alignment between the reference and test images.