Void rectangle(Image img, Int x1, Int y1, Int x2, Int y2, Colour col, Bool filled=false)
img: The image
x1: X coordinate of first corner
y1: Y coordinate of first corner
x2: X coordinate of opposite corner
y2: Y coordinate of opposite corner
col: Colour of the rectangle's border
filled: If this is true, the rectangle will be filled with the same colour as the border.
Draws a rectangle with opposite corners at (x1,y1) and (x2,y2).