COPE's guidance in the form of a flowchart on what to do if you suspect that images in a published article have been manipulated.
This flowchart relates only to cases where concerns related to digital photographic images are raised (eg, duplication of parts within an image, or use of identical images to show different things). For wider concerns about potential data fabrication, please consult the flowchart Suspected fabricated data in a published manuscript.
The Image manipulation flowchart offers guidance in steps to take when there is a suspicion of image manipulation, including who to contact and when to consider a retraction or correction.