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    • 50. 发明授权
    • Detection technique for digitally altered images
    • 用于数字改变图像的检测技术
    • US08260067B2
    • 2012-09-04
    • US12421949
    • 2009-04-10
    • Yun-Qing ShiBin Li
    • Yun-Qing ShiBin Li
    • G06K9/36G06K9/38G06K9/46
    • H04N19/60H04N19/865
    • Techniques are generally described to determine whether a JPEG image has undergone two compressions. Probabilities can be computed for the first digits of quantized DCT (discrete cosine transform) coefficients from a set of AC (alternate current) modes to detect or determine whether the JPEG image has undergone two compressions. The set of AC modes may include a predetermined number of distinguishable AC modes where a distinguishable AC mode may be an AC mode in which a second quantization step (QS2) is not an integer multiple of the first quantization step (QS1). Classifiers may be created during a training process, and later may be used to assist in determining whether a suspect JPEG image has undergone two compressions. When the classifiers support a multi-classification system, described detection techniques may also be arranged to determine a primary quality factor for the double compressed JPEG image.
    • 通常描述技术来确定JPEG图像是否经历了两次压缩。 可以从一组AC(交替电流)模式的量化DCT(离散余弦变换)系数的第一位计算概率,以检测或确定JPEG图像是否经历了两次压缩。 AC模式的集合可以包括预定数量的可区分AC模式,其中可区分AC模式可以是其中第二量化步长(QS2)不是第一量化步长(QS1)的整数倍的AC模式。 可以在训练过程中创建分类器,并且稍后可以用来帮助确定可疑JPEG图像是否经历了两次压缩。 当分类器支持多分类系统时,还可以安排所描述的检测技术来确定双压缩JPEG图像的主要品质因子。