Abstract: Unsharp masking (USM) sharpening is a common operation to improve image visual clarity in image edition,However, it can cause serious harm if applied to scenarios involving the tampering of forensic evidence or public event photographs. In recent years, many methods for USM sharpening and anti-sharpening in digital image forensics have been proposed by researchers. So, a systematic review of the literature in this field is provided by this paper. The fundamental principles of the USM sharpening operation are first explained in this paper, followed by the categorization and summary of existing USM sharpening and anti-sharpening methods based on algorithm implementation principles. Additionally, commonly used datasets in related literature are introduced, and performance evaluations of existing methods are conducted for comparative purposes. Finally, the challenges faced by existing methods are analyzed and future research directions are discussed, mainly including the use of updated datasets, in-depth research on the game of forensics and anti-forensics, in-depth research on sharpening anti-forensics, the issue on the efficiency of forensics scheme execution, and the improvement of the reliability of anti-forensics.

Key words: unsharp masking, USM sharpening, sharpening forensics, sharpening anti-forensics, digital image forensics