A color image fragile watermarking algorithm based on DWT-DCT

Discrete wavelet transform (DWT) and discrete cosine transform (DCT) algorithm combined is used in fragile watermark embedding to achieve the color image content integrity protection. When embedding watermark, the original image is color converted first and then the brightness component is three discrete wavelet decomposed. Extract low-frequency approximation sub-graph and vertical high-frequency detail sub-images coefficient, divide into blocks, and then discrete cosine transform. Using low-frequency approximation sub-graph transformation coefficients replace high-frequency detail sub-images transformation coefficients. When detecting watermark, by comparing replaced part coefficient we can determine whether the image has been tampered. Simulation results show that the algorithm has strong detection and location capability and strong ability of anti-JPEG compression and maintain better original image quality.