MATLAB Implementation of DCT-Based Watermarking

The DCT watermarking method described here presents a straightforward and practical algorithm that operates in the DCT domain using 8x8 block partitioning. This implementation focuses on embedding watermark images of size 64x64 into host images. The core algorithm involves dividing the host image into 8x8 blocks and applying Discrete Cosine Transform (DCT) to each block. Watermark embedding is typically performed by modifying specific DCT coefficients in the middle frequency range to balance robustness and visual quality. Key MATLAB functions used in implementation include dct2() for forward DCT transformation, idct2() for inverse transformation, and blockproc() for efficient block-wise processing. The implementation follows these main steps: image preprocessing, block segmentation, DCT coefficient selection, watermark data embedding through coefficient modification, and inverse DCT transformation to reconstruct the watermarked image. This approach ensures the watermark survives common image processing operations while maintaining acceptable visual quality in the host image.