I had this same error with a library that a friend of mine wrote in C++ on Linux. The way I figured out what the C# error was ACTUALLY saying was I used Dependency Walker.
Basically, you download that program, open it, and open the FreeImage DLL with that program. It’ll scan it and look for missing dependencies. If it finds some, it’ll tell you. It’ll list all DLL files that the library is looking for but couldn’t find. Just google the file names and in most cases you should find downloads for the relevant libraries.
From what I can see you’re missing VCOMP120.DLL (see the yellow question mark next to it?)
I’m not a Windows user myself (well, not entirely true. I just switched to linux a few days ago, won’t ever be going back) but from a little bit of googling all I could really find is “Try rebooting your system to clear out any software conflicts caused by installing new programs/updates.” Typical Windows troubleshooting guides.
But, in case you haven’t rebooted after installing VC++ 2012 Redistributable, I’d give your computer a nice reboot and then try using the pipeline again to build the PNGs. If there’s still an error then…as I said I’m not really a Windows user anymore so I’m not REALLY the best person to help out with this stuff
Edit: IESHIMS.DLL’s another one that’s missing. Didn’t catch that one at first. No idea what the hell that is or what it does.
You don’t need to put the vcomp120.dll INSIDE FreeImage.dll. That’s not how DLLs work.
Also this isn’t the fault of C# or monogame itself. This is the fault of Windows - one of the main reasons I switched from it to Linux. Windows’ package/library management is absolutely horrible.