Digital Watermarking Algorithm for Pixel Flipped Text Image based on Calculus Operator

In order to encrypt and watermark the pixel flipped text image, a digital watermarking algorithm for pixel flipped text image based on calculus operator is proposed. The original image is evenly divided into blocks, and subsequently then the sub block is subjected to the fundamental wave transformation of the calculus operator. The embedding position is determined by combining the characteristics of the human visual system (HVS) and the parity quantization algorithm. The watermark information is embedded into the sub block, and the differential operator is used to perform the inverse ridgelet transformation on the sub block to obtain the watermark image. The sum of the absolute differences of adjacent pixels is used to calculate the correlation, and the pixel fluctuation function is designed to improve the accuracy of image restoration and the embedding capacity and expand the key space. The mean value of histogram is used as the calibration point to avoid the possibility of synchronization attack through synchronous embedding and detection process. The watermark information is added to the low frequency part of the image to enhance the robustness of the watermark. The watermark information is added to the low frequency part of the three -level lifting wavelet decomposition of the image, and the three -level lifting wavelet inverse transform is performed according to the wavelet coefficients after embedding the watermark information, so as to obtain the color image fraction containing the watermark, and achieve the digital watermark acquisition of pixel flipped text image. The simulation results show that the proposed method is robust for extracting digital watermark from pixel flipped text images, achieves blind inspection of watermark images with high security. The quality of watermarked images with different embedding capacities is good, and the watermark information can be completely extracted. Compared with other methods, better watermark embedding rate, extraction accuracy and robustness is seen with the proposed method. (C) 2024 Society for Imaging Science and Technology.