Displacement JPEG (joint photographic experts group) double-compression tampering blind detection method based on condition symbiotic probability matrix

The invention relates to a displacement JPEG (joint photographic experts group) double-compression tampering blind detection method based on a condition symbiotic probability matrix. The method comprises the steps: firstly, carrying out differential and thresholding treatment of horizontal, vertical, main diagonal and secondary diagonal directions on an amplitude matrix of a discrete cosine transform coefficient quantified by a JPEG; then modeling the four thresholding differential matrixes by the condition symbiotic probability matrix; selecting an element of the condition symbiotic probability matrix as characteristic data, and carrying out dimension reduction treatment on the characteristic data by principal component analysis; and finally, judging whether an image block is subjected to displacement JPEG double-compression through a support vector machine technology. An experiment shows that the method has obvious advantages compared with the existing algorithm when the image block is small, so that the practicability of the displacement JPEG double-compression tampering detection is greatly improved, and good foundation is established for further development of the digital image forensics field.