If you're unable to find the solutions manual on GitHub, you can try checking:
Official solutions for the 4th edition are primarily managed through ImageProcessingPlace , the book's companion site. icemansina/CUHKSZ_DIP - GitHub digital image processing 4th edition solutions pdf github
MohsenEbadpour/Digital-Image-Processing-DIP-Course-Homeworks FlagArihant2000/dip-notes programming language like Python or MATLAB? If you're unable to find the solutions manual