Frequency domain watermarking of medical images based on fractional discrete Cosine, Mellin, and Schur transforms
摘要
Protecting medical images in interconnected healthcare systems requires maintaining both diagnostic integrity and secure verification. This study presents a watermarking framework combining deep feature extraction, chaotic cryptography, adaptive frequency-domain embedding, and AI-assisted extraction. Deep convolutional networks identify perceptually tolerant regions for content-aware embedding while preserving vital diagnostic areas. Hybrid chaos-based encryption secures watermark data against unauthorized recovery. The embedding operates in the fractional discrete cosine transform (FDCT) domain with adaptive coefficient selection and multi-objective optimization balancing imperceptibility, robustness, and capacity. During extraction, a convolutional autoencoder refines recovered watermarks, maintaining fidelity under compression, noise, and geometric distortions. Experimental validation on medical datasets demonstrates high embedding capacity (0.07309 BPP), excellent visual similarity (PSNR = 46.85 dB, SSIM = 0.9995), and strong resilience against attacks (NCC ≥ 0.94), ensuring secure and compliant medical image transmission.