A watermarking algorithm of color images based on the quaternion Fourier Transform (QFFT) and improved
quantization index algorithm (QIM) is proposed in this paper. The original image is transformed by QFFT, the
watermark image is processed by compression and quantization coding, and then the processed watermark image is
embedded into the components of the transformed original image. It achieves embedding and blind extraction of the
watermark image. The experimental results show that the watermarking algorithm based on the improved QIM algorithm
with distortion compensation achieves a good tradeoff between invisibility and robustness, and better robustness for the
attacks of Gaussian noises, salt and pepper noises, JPEG compression, cropping, filtering and image enhancement than
the traditional QIM algorithm.