I was working on a project that had images stored on a server. The images were stored in a folder that I only had read-only rights to.
I copied the folder and used them in InDesign but was not able to edit the images in Photoshop.
I tried changing the permissions from the Terminal command line with chmod, but that didn’t work, nor did the unlock in Get Info.
Here’s how I was able to do it:
I opened the images in Preview. At the top, near the file name it says “Locked.” I click the unlock box and Preview just spins and spins. I force quit Preview and open the images in Photoshop. Problem solved!
I don’t know how this works, but it worked. If you have a similar problem give it a try. I used a Mac running Yosemite, Photoshop CC 2017 and Preview 8.1.