TPNGImage help

Called when the user released the mouse button on the image.

type TMouseButton = (mbLeft, mbRight, mbMiddle);
type TShiftState = set of (ssShift, ssAlt, ssCtrl, ssLeft, ssRight, ssMiddle, ssDouble);
event OnMouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);

Description
Called when the user has released the button button after having pressed over the button.
Button is the button that the user has pressed; shift contains the state of other keys that the user has pressend and finally X and Y are the position relative to the button upper-left boundaries that the user pressed the mouse button on.

See also OnMouseDown.