This should do it. Again, this is setup for Chrome, and wouldn't work if the "Save image as..." menu item isn't there or doesn't accept the letter v to invoke that menu item.
--Prevent mouse/keyboard input to prevent interfering with script
--Move the mouse to where the gesture started
--Click the right mouse button to open the context menu
acMouseClick(gsx, gsy, 0, 1, 1)
--Pause for the menu
--Send the "V" key, which in Chrome selects the "Save image as..." menu item
--Stop blocking input