If you want to take picture from active movie then press Ctrl + I on keyboard
After this you will see a new pop up window , then save this picture by giving any name .
Or in Gom player , you can first select screen capture from below central button and then copy by pressing prtscn sysrq left side button F 12 ( print screen ) and then open paint and then past it by pressing ctrl + V and save the file by pressing Ctrl + s