Turtle Graphics  Turtle graphics provide a simple way to draw pictures in a window.  The name suggests the way in which we can think about the drawing process.  Imagine a turtle walking around a screen with a pen tied to it’s tail. Commands tell it to move and to put the pen up and down (i.e. put it’s tail up and down.)  This is a primitive form of graphics but gives us a good introduction to graphic concepts.

Example TurtleGraphics Program import TurtleGraphics.StandardPen; public class DrawSquare { public static void main(String [ ] args) { StandardPen pen = new StandardPen(); pen.up();pen.move(25);pen.turn(90);pen.move(25);pen.down(); pen.turn(90); pen.move(50); }}

Example Program Explanation import TurtleGraphics.StandardPen;  Imports the TurtleGraphics package which allows us to draw basic shapes.  StandardPen is the class we will be using.

Example Program Explanation pen.up( ); pen.move(25); pen.turn(90); pen.move(25); pen.down( );  These statements lift the pen, move it to the square’s top left corner, and lower to set it to draw.

Example Program Explanation pen.turn(90); pen.move(50);  These statements draw a square with side length of 50 pixels. Each turn forms the 90° turn at the corners.

Turtle Graphics Pen Messages Pen Message What it Does home() The pen jumps to the center of the graphics window without drawing and points north. setDirection(degrees) The pen points in the indicated directions. Due east corresponds to 0 degrees, north to 90, west to 180 and south to 270. turn(degrees) The pen adds the indicated degrees to its current direction. Positive degrees correspond to turning counterclockwise. The degrees can be integer or floating point. down() The pen lowers itself to the drawing surface up() The pen raises itself from the drawing surface move(distance) The pen moves the specified distance in the current direction. The distance can be an integer or floating- point number and is measured in pixels.

Misc. Statements on Turtle Graphics  When the StandardPen is instantiated, it is always:  In the center of the graphics window  In the down position  Pointing North.

Additional TurtleGraphics Features Pen Message What it Does setColor(Color. color) Sets the pen’s color to the specified color. import java.awt.Color; setWidth(width as int.) Sets the pen’s width to the specified width. Must be an integer. move(double x,double y) Moves the pen to the specified location relative to home(0, 0)

TurtleGraphics Color Constants  The Color class has a number of different colors available.  import java.awt.Color; redred yellowyellow blueblue orangeorange pinkpink cyancyan magentamagenta blackblack whitewhite graygray light graylight gray dark graydark gray

Setting color and width of pen Example //imports needed packages import TurtleGraphics.StandardPen; import java.awt.Color; public class DrawSquareColor //Start of class { public static void main(String [] args) //Start of Main method { StandardPen pen = new StandardPen(); //Instantiates a pen object pen.setColor(Color.red);pen.setWidth(3); pen.turn(90); pen.move(50); pen.setColor(Color.magenta);pen.setWidth(6);pen.move(50);}}