Keypress.ino

// Arduino Leonardo: Send key when a button is pressed.

void setup() {
  pinMode(12, INPUT_PULLUP);
  Keyboard.begin();
}

void loop() {
  //if the button is pressed
  if(digitalRead(12)==LOW){
    Keyboard.press(KEY_LEFT_ALT);
    Keyboard.press(KEY_F12);
    delay(100);
    Keyboard.releaseAll();
    delay(200);
  }
}