I am running Android 12 on a Galaxy A12 phone. Recently, out of the blue, image files that I transfer to my phone from my computer have been having the following problem:
At first, right after I transfer them, they are OK. I can view them in Gallery. When I'm done, I'll close that app. Later, I'll need to view them again, so I'll go back into gallery, but they will be corrupted. Gallery will just tell me "Unsupported Media" or some such nonsense and refuse to display them. I can transfer them over from the computer again, replacing the corrupted files, and they will work again for my first session of viewing them... and then they won't.
This never used to be a problem.
I am saving them to my external SD card. I have not tried saving them on the phone's internal storage, but that would not be feasible. My internal storage is tight, and I need to conserve it. The images happen to be PNG format images. That is what I use most commonly. I avoid JPEG due to it being a lossy format. But I CAN verify that this problem happens to GIFs as well.
I have tried using Gimp on my computer to open and resave the original images in the hopes that there was just something odd about the files, and Gimp would save them "properly". That actually worked for a few of them for a while, so I thought that that was the problem, but then even that stopped fixing them. Even my gimp-saved images started doing this.
I have tried installing and using several other gallery apps in the hopes that the default one was just stupid, but no luck. Nothing can view them once they spontaneously corrupt like this. I don't even know what causes them to go corrupt. Sometimes they will work for a few viewing sessions, quitting and restarting the Gallery and coming back to view them later a few times. Sometimes they will go bad after the first session. I can never predict when they will die.
Even more confusing, sometimes the thumbnail will become corrupt along with the image, causing the Gallery to display a blank icon both when listing images and viewing individual ones, and sometimes only the full image will get corrupted, so that I can see the thumbnail in lists, but not the full-screen image when I try to view it. It is completely unpredictable which images will do which.
I am at a complete loss here. Has anyone ever encountered this and/or does anyone know what is happening?
EDIT: I should also mention that any images saved before this started happening don't get corrupted. This only happens to images newly transferred after the problem started.