一种估计JPEG双重压缩原始量化步长的新方法

该文提出了一种双重压缩后JPEG图像的原始量化步长的估计方法.该方法根据两次量化步长之间的大小关系分3种情况进行讨论.当原始量化步长大于第2次量化步长,提出了直接利用直方图计算的新方法;为解决原始量化步长是第2次量化步长因子和傅里叶频谱分析中的多值问题,提出了采用0.98缩放来近似未压缩图像的方法.本文方法能给出第二次量化步长为一次量化步长倍数时的估计,并利用频谱分析的结果降低了计算的复杂度,实验结果表明本文方法有较高的估计准确度.

A New Method for Estimating the Primary Quantization Step of JPEG Double-Compression

This paper presents a method for estimating the primary quantization step of double compressed JPEG image. The method in accordance with the relationship between the two quantization steps contains three situations. When the primary quantization step is larger than the second quantization step, the histogram can be used to calculate directly. To resolve the issue of multi-value caused by Fourier spectrum analysis and the problem that the primary quantization step is the factor of the second quantization step, the uncompressed image can be approximated by narrowing the image by 98%. This method can resolve the problem that the primary quantization step is the factor of the second quantization step, and uses spectrum analysis to reduce the complexity. The experimental results show that this method has higher accuracy of the estimation.