This invention discloses a robust zero-watermarking method and
system for medical images based on local minimum adaptive two-dimensional empirical
wavelet transform (2DEWT), polar
harmonic transform (PHT), and
Gabor transform. The method includes the following steps: Step 1, copyright
watermark encryption process; Step 2, copyright
watermark embedding process; Step 3, copyright
watermark extraction process; Step 4, copyright watermark decryption process; Step 5, copyright
system usage process. This invention uses 2DEWT in the extraction of medical image features and, based on the characteristics of medical images, designs an adaptive improvement strategy that directly uses the local minimum points of the
frequency domain energy curve as sub-band boundaries. The local minimum points are essentially the boundary points of different feature components in the
frequency domain of medical images: the boundaries between low-frequency global structures and high-frequency
lesion details, and the boundaries of
lesion textures in different directions (such as
blood vessel orientation and
lesion edge angles) all exist in the form of local minimum points. Two-dimensional empirical
wavelet transform is performed on medical images to extract low-frequency subbands.
Gabor transform is applied to the low-frequency subbands, and PHT is applied to the high-frequency subbands. Image features are obtained through
feature fusion, and the copyright watermark is embedded by obtaining the key through XOR with the copyright watermark.