The first question was the other way around; Is your screenshotcaptor running with administrator rights by accident? In that way it can't intercept the hotkeys from your normal windows user-session.

By default, what you want is how it normally works.
Are you running SSC using the Run as Administrator option? (Can be set at the shortcut, manually) or use a replacemant tool for UAC (as deployed in some corporate controled computers)

What programming language have you tried?
You should use the best tool for the job:
Most suitable to process would be JS (Javascript), as that's what the first 2 letters of the word JSON come from... Node.js should be the way to go for a command-line tool.
Next choice up (assuming a Windows OS) should be C#/.NET as that makes it very easy using one of the JSON libraries (NewtonSoft comes to mind)
And the runner up would probably be Java, but there are some that don't like that (for probably the wrong reasons), where also plenty of libraries are available, org.json and Google GSON are popular choices.