A method and device for estimating the first compression quantization step size of jpeg double compressed images

Abstract

The invention provides a method and device for evaluating a first-compression quantification step size of a JPEG (Joint Photographic Experts Group) double-compressed image and is used for improving the accuracy of evaluating the first-compression quantification step size of the JPEG double-compressed image. The method comprises the steps of extracting a basic feature C <i, j> corresponding to any frequency f <i, j> of a to-be-evaluated JPEG double-compressed image; through combination of an anti-forensics technology, extracting a secondary feature C ' <i, j> corresponding to the any frequency f <i, j>; carrying out series connection on the basic feature C <i, j> and a difference value C <i, j>-C ' <i, j> between the basic feature C <i, j> and the secondary feature C ' <i, j>, thereby obtaining a combined feature; and inputting all combined features of the to-be-evaluated JPEG double-compressed image into a first-compression quantification step size evaluator, thereby obtaining an evaluation value of the first-compression quantification step size of the JPEG double-compressed image. Compared with the prior art, the technical scheme provided by the method and the device have the advantage that a utilization rate of judgment information is higher when whether the JPEG image is tampered or not is detected, and the higher detection precision can be obtained.

Description

technical field [0001] The invention belongs to the field of image processing, in particular to a method and a device for estimating the first compression quantization step size of a JPEG double compressed image. Background technique [0002] With the widespread use of image editing software, the web is flooded with more and more doctored images. Joint Photographic Experts Group (JPEG) is one of the most commonly used image compression standards, therefore, tampering detection for JPEG images has attracted people's attention. The estimation of the detection and compression parameters of JPEG double compression, for example, the estimation of the quantization step size of the first compression of JPEG double compression image is one of the important means to analyze the history of JPEG image tampering, which is based on the following scenarios or facts, namely: After a certain part of a JPEG image (assumed to be image A) is cropped and stitched to another uncompressed image ...

AI Technical Summary

Problems solved by technology

[0004] Since JPEG image compression is lossy compression, when the compression strength of the second compression of JPEG image increases, the loss of information increases, and the masking effect of the first compression of JPEG image is also strong, thus increasing the difficulty of detection

In other words, the disadvantage of the method provided by the above-mentioned prior art is that when the compression intensity of the second compression of the JPEG image is relatively large, the DCT coefficient distribution has a weak ability to reflect the change of the quantization step size. Therefore, when the quantization step size to be estimated is large When the value is large, the accuracy of the first pressure quantization step estimation becomes lower

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