Blind estimation method of rotation angles of digital images

Abstract

The invention relates to a blind estimation method of rotation angles of digital images. If rotary gray level images are color images, luminance components are obtained after spatial alternation of YCbCr, difference images are obtained by conducting second order difference or laplace filtering on images to be detected, and the difference images are processed line by line (or row by row); a vector quantity V with the length of N0 is obtained after zero filling at the tail end, and the N0 is integer power of 2; the discrete Fourier transform of the V is obtained, the magnitude spectra D=|DFT(V)| is obtained; the D is searched, if the D(k) is a maximum value in a neighborhood region [k-delta, k+delta], and a peak value counter c(k)=c(k)+1. Normalization is carried out on the c(k) to obtain a frequency-peak value counting picture, and the rotation angles of the images can be determined by detecting the frequency corresponding to the peak value. Blind estimation can be achieved without priori knowledge such as original images before rotation or reference templates, the blind estimation method is basically not influenced by image joint photographic expert group (JPEG) compression storage quality factors, the algorithm complexity is low, detection precision is high, size of the images is big, and estimated accuracy is high.

Description

technical field [0001] The invention relates to a digital image processing technology, in particular to a method for blindly estimating the rotation angle of a digital image. Background technique [0002] Rotation is a routine operation in digital image processing. In applications such as image registration and image stitching, the estimation of rotation angle plays an important role. In the study of digital watermarking, geometric attacks on watermarks, especially rotation attacks, make it difficult to extract watermarks from images. Therefore, blind estimation of rotation angles is also important in combating geometric attacks. With the increasing popularity and ease of operation of image processing software, it is becoming more and more difficult to detect malicious tampering of images (especially carefully crafted synthetic images), and the process of synthetic tampering of images is usually accompanied by image scaling and rotation. Detecting the rotation characterist...

AI Technical Summary

Problems solved by technology

[0031] The present invention aims at the problem that the current image blind detection is only qualitative and cannot be quantified, and proposes a blind estimation method of digital image rotation angle, which can realize blind estimation without prior knowledge such as the original image before rotation or a reference template

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