Purely chromatic background images are widely used in computer wallpapers and advertisements, leading to issues such as copyright infringement and the loss of interest of holders. Image hashing is a technique used for comparing the similarity between images, and is often used for image verification, search, and copy detection due to its insensitivity to subtle changes in the original image. In a purely chromatic background image, the central detail of the image is the primary part and the key for copyright authentication. As the perception hash (pHash) algorithm only retains the low-frequency portion of the discrete cosine transform (DCT) matrix, it is unsuitable for purely chromatic background images. To deal with this issue, we propose an improved perception hash (ipHash) algorithm to enhance the universality of the algorithm by extracting purely chromatic background image features. Meanwhile, the development of image hashing is restricted due to the requirement of a trusted third party. To solve this issue, a secure blockchain-based image copyright protection scheme is designed. It realizes the copyright authentication and traceability, and overcomes the issue of a lack of trusted third parties. Experimental results show that the proposed method outperforms the state-of-theart image copyright protection schemes.