JPEG compression history estimation for color images
JPEG compression history estimation for color images
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DOI：
10.1109/icip.2003.1247227
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发表时间：
2003-11
影响因子：
10.6
通讯作者：
R. Neelamani;R. Queiroz;Z. Fan;S. Dash;Richard Baraniuk
中科院分区：
文献类型：
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作者：
R. Neelamani;R. Queiroz;Z. Fan;S. Dash;Richard Baraniuk
我们经常遇到以前使用联合图像专家组（JPEG）标准压缩的数字彩色图像。在图像当前表示的过程中，以前JPEG压缩的各种设置（称为JPEG压缩历史记录（CH））通常在JPEG解压缩步骤后被丢弃。给出了一个JPEG压缩的彩色图像，本文的目的是估计其丢失的JPEG CH。我们观察到，以前的JPEG压缩的量化步骤在离散余弦变换（DCT）域中引入了一个晶格结构。本文提出了两种方法，利用这种结构来解决JPEG压缩历史估计（CHEst）的问题。首先，我们设计了一个基于统计字典的CHEst算法，测试字典中的各种CH，并选择最大的后验估计。其次，对于DCT系数紧密符合3-D平行六面体格的情况，我们设计了一个盲的基于格的CHEst算法。盲算法利用的事实，JPEG CH编码在近正交基的3-D格，并采用新的格算法和最近的结果近正交格基估计CH。这两种算法提供了强大的JPEG CHEst性能在实践中。仿真表明，JPEG CHEst可以是有用的JPEG再压缩;估计CH允许我们再压缩JPEG解压缩图像以最小的失真（大的信号噪声比），同时实现一个小的文件大小。
We routinely encounter digital color images that were previously compressed using the Joint Photographic Experts Group (JPEG) standard. En route to the image's current representation, the previous JPEG compression's various settings-termed its JPEG compression history (CH)-are often discarded after the JPEG decompression step. Given a JPEG-decompressed color image, this paper aims to estimate its lost JPEG CH. We observe that the previous JPEG compression's quantization step introduces a lattice structure in the discrete cosine transform (DCT) domain. This paper proposes two approaches that exploit this structure to solve the JPEG Compression History Estimation (CHEst) problem. First, we design a statistical dictionary-based CHEst algorithm that tests the various CHs in a dictionary and selects the maximum a posteriori estimate. Second, for cases where the DCT coefficients closely conform to a 3-D parallelepiped lattice, we design a blind lattice-based CHEst algorithm. The blind algorithm exploits the fact that the JPEG CH is encoded in the nearly orthogonal bases for the 3-D lattice and employs novel lattice algorithms and recent results on nearly orthogonal lattice bases to estimate the CH. Both algorithms provide robust JPEG CHEst performance in practice. Simulations demonstrate that JPEG CHEst can be useful in JPEG recompression; the estimated CH allows us to recompress a JPEG-decompressed image with minimal distortion (large signal-to-noise-ratio) and simultaneously achieve a small file-size.