One way that could be given a go, is to actually visualize that image consciously (if you would reasonably comfortable doing so) and change the negative narrative associated with it to a progressively positive one.
Not an easy process at first, but it is like confronting fears. It gets easier as time goes on.
I too have a photographic memory, and there are some haunting things I have observed directly in the past that I have employed this method for.
Some challenging visual memories can need the assistance of someone 'qualified' to assist a desensitizing process.
When desensitization has been achieved, these troubling visual memories can be 'put in a mental box' (a control box) where you are in control of where and when such a memory will be noted again and you have positive control of how it affects you in the future.
Hope that all made sense ;)