基于相机标定的文字变造篡改鉴定

数字照片中的汉字经过数码相机拍摄都会符合一定的投影规则,经过变造篡改的汉字则存在一定程度的投影偏差.为了检测数字图像中汉字信息的真实性,对估算汉字投影偏差法进行了研究,提出了基于相机标定来估算投影偏差值的检测技术.结合汉字具有平面方块的特点,利用汉字模型代表真实世界坐标系下被拍摄的汉字,提取一定数量的对应点坐标,获取与图像实际单应性矩阵对应的投影矩阵,求解重构汉字的偏差值.通过实验确定偏差阈值,图像中汉字投影偏差值大于阈值则认为经过变造篡改.实验结果表明,该方法能检测重新写入图像的汉字和替换图像汉字的篡改.

Forgeries of Chinese Character Detecting Based on Camera Calibration

Chinese characters should match certain rules of projection when photoed by digital camera. Meanwhile that will bring projection deviations. In order to detect the information authenticity of the Chinese characters in the digital image, a new estimation algorithm for Chinese characters projection deviation is studied. Based on camera calibration, a new estimation of projection deviation is proposed. And based on Chinese characters’ flat square feature, using Chinese characters model, instead of shooting Chinese characters into the real world, can be coordinated, a set of corresponding point coordinates is extracted, and then the corresponding affine matrix of the image’s homography matrix is obtained. Thus, the deviation value of the reconstruction Chinese character is calculated. If the value obtained is greater than threshold established by experiments before, the Chinese characters in this digital image will be manipulated. Experiments show that this method can detect the rewritten or replaced Chinese characters in the digital image.