Explain custom points from which to transform

README.md

@@ -42,9 +42,10 @@ corners = [
     (window.width, window.height), # Top right
 ]
 pins = PygletCornerPin(window, corners)
-
 ```
 
+Moreover, you don't need to pin the window _corners_, but can pin from any four arbitrary points, by providing `source_points`.
+
 Run [pattern.py](examples/pattern.py) in the examples folder for a demo.
 
 To use the keyboard, select a pin with number keys 1-4, the use the arrow keys (optionally with ctrl/shift modifier) to move the handle.

examples/pattern.py

@@ -26,10 +26,9 @@ for i in range(y_steps+3):
 def on_key_press(symbol, modifiers):
     if symbol == pyglet.window.key.Q or symbol == pyglet.window.key.ESCAPE:
             window.close()
-            exit()
 
 
-pins = PygletCornerPin(window, corners=[[100,100],[800,100],[150,500], [300,300]], source_points=[[100,100], [700,100], [100,500], [300,300]])
+pins = PygletCornerPin(window, source_points=[[100,100],[600,100],[100,300], [600,300]], corners= [[100, 100], [444, 155], [230, 250], [600, 300]])
 # event handlers for dragging:
 window.push_handlers(pins)
 
@@ -43,3 +42,6 @@ def on_draw():
 
 
 pyglet.app.run()
+
+print(f"point positions: {pins.pin_positions}")
+print("Save these and pass them as 'corner' attribute to restore last position.")