This is my screenshot tool that I use to take screenshots (Windows only, OpenCL required) by pressing Ctrl-F1 (combo can be changed). As with all my projects it depends on rouziclib for all the heavy lifting.
I recommend you download the latest binary (Windows only) here. Don’t forget to keep SDL2.dll together with screenshot.exe.
When you first start the program it briefly flashes then you see nothing. It hides itself immediately while it waits for the hotkey, which is set to Ctrl-F1 by default but can be changed using the "Set hotkey" dialog. I put a shortcut to screenshot.exe in my Windows startup folder shell:startup (you can enter that in the Windows Explorer address bar) so it unobtrusively stays hidden in the background waiting (in a blocked way so it doesn’t consume any CPU time at all) for you to press Ctrl and F1 together.
I shouldn’t need to explain what the resizing control does, you just need to drag the squares around to reshape the selection. The Reset button resets the selection, the Reuse prev sel restores the previous selection that was saved the last time that the interface was hidden so that selections can quickly be reused, and the Preview checkbox allows you to see the cropped image at full brightness (the image is otherwise darkned to make the controls more visible) without controls. Currently only the main screen is captured, other screens are ignored.
The interface is zoomable as explained here. Basically by clicking the middle mouse button you enter the zoom-scroll mode so you can zoom (using the scroll wheel) and adjust the selection with more precision. You exit that mode by clicking the middle mouse button again or better yet reset the view by holding the middle mouse button for at least half a second.
By default the output folder is "My Pictures", you can change it by typing or better yet pasting a different path (such as C:\screenshots for instance), and you can use the "Open 📁" button to open the folder in Windows.
Both the "Save screenshot" and the Return key of your keyboard save the cropped screenshot. If the file saved correctly then the program will hide itself again and wait for the next time you press Ctrl-F1. If the output path or filename is incorrect then the filename and save button will flash red, meaning that there is something wrong with the output path (a folder doesn’t exist or the file extension is wrong, or a file with the same path cannot be overwritten) and you need to fix it. Note that you can well output to a subfolder by adding the subfolder to the Filename field, for instance by having game screenshots\screenshot.jpg.
The output file is a PNG file by default, however you can also make it a JPG file by replacing the extension in the Filename field. JPG files have a quality preset of 92.
By default the interface is full screen so that it seemlessly transitions from your desktop to the program. However you can press Alt-Return to switch between full screen or windowed mode.