package stdlib;
/* ***********************************************************************
 *  Compilation:  javac StdDraw.java
 *  Execution:    java StdDraw
 *
 *  Standard drawing library. This class provides a basic capability for
 *  creating drawings with your programs. It uses a simple graphics model that
 *  allows you to create drawings consisting of points, lines, and curves
 *  in a window on your computer and to save the drawings to a file.
 *
 *  Todo
 *  ----
 *    -  Add support for gradient fill, etc.
 *
 *  Remarks
 *  -------
 *    -  don't use AffineTransform for rescaling since it inverts
 *       images and strings
 *    -  careful using setFont in inner loop within an animation -
 *       it can cause flicker
 *
 *************************************************************************/

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.image.*;
import java.io.*;
import java.net.*;
import java.util.LinkedList;
import java.util.TreeSet;
import javax.imageio.ImageIO;
import javax.swing.*;

/**
 *  <i>Standard draw</i>. This class provides a basic capability for
 *  creating drawings with your programs. It uses a simple graphics model that
 *  allows you to create drawings consisting of points, lines, and curves
 *  in a window on your computer and to save the drawings to a file.
 *  <p>
 *  For additional documentation, see <a href="http://introcs.cs.princeton.edu/15inout">Section 1.5</a> of
 *  <i>Introduction to Programming in Java: An Interdisciplinary Approach</i> by Robert Sedgewick and Kevin Wayne.
 */
public final class StdDraw implements ActionListener, MouseListener, MouseMotionListener, KeyListener {

  // pre-defined colors
  public static final Color BLACK      = Color.BLACK;
  public static final Color BLUE       = Color.BLUE;
  public static final Color CYAN       = Color.CYAN;
  public static final Color DARK_GRAY  = Color.DARK_GRAY;
  public static final Color GRAY       = Color.GRAY;
  public static final Color GREEN      = Color.GREEN;
  public static final Color LIGHT_GRAY = Color.LIGHT_GRAY;
  public static final Color MAGENTA    = Color.MAGENTA;
  public static final Color ORANGE     = Color.ORANGE;
  public static final Color PINK       = Color.PINK;
  public static final Color RED        = Color.RED;
  public static final Color WHITE      = Color.WHITE;
  public static final Color YELLOW     = Color.YELLOW;

  /**
   * Shade of blue used in Introduction to Programming in Java.
   * It is Pantone 300U. The RGB values are approximately (9, 90, 166).
   */
  public static final Color BOOK_BLUE       = new Color(  9,  90, 166);
  public static final Color BOOK_LIGHT_BLUE = new Color(103, 198, 243);

  /**
   * Shade of red used in Algorithms 4th edition.
   * It is Pantone 1805U. The RGB values are approximately (150, 35, 31).
   */
  public static final Color BOOK_RED = new Color(150, 35, 31);

  // default colors
  private static final Color DEFAULT_PEN_COLOR   = BLACK;
  private static final Color DEFAULT_CLEAR_COLOR = WHITE;

  // current pen color
  private static Color penColor;

  // default canvas size is DEFAULT_SIZE-by-DEFAULT_SIZE
  private static final int DEFAULT_SIZE = 512;
  private static int width  = DEFAULT_SIZE;
  private static int height = DEFAULT_SIZE;

  // default pen radius
  private static final double DEFAULT_PEN_RADIUS = 0.002;

  // current pen radius
  private static double penRadius;

  // show we draw immediately or wait until next show?
  private static boolean defer = false;

  // boundary of drawing canvas, 5% border
  private static final double BORDER = 0.05;
  private static final double DEFAULT_XMIN = 0.0;
  private static final double DEFAULT_XMAX = 1.0;
  private static final double DEFAULT_YMIN = 0.0;
  private static final double DEFAULT_YMAX = 1.0;
  private static double xmin, ymin, xmax, ymax;

  // for synchronization
  private static Object mouseLock = new Object();
  private static Object keyLock = new Object();

  // default font
  private static final Font DEFAULT_FONT = new Font("SansSerif", Font.PLAIN, 16);

  // current font
  private static Font font;

  // double buffered graphics
  private static BufferedImage offscreenImage, onscreenImage;
  private static Graphics2D offscreen, onscreen;

  // singleton for callbacks: avoids generation of extra .class files
  private static StdDraw std = new StdDraw();

  // the frame for drawing to the screen
  private static JFrame frame;

  // mouse state
  private static boolean mousePressed = false;
  private static double mouseX = 0;
  private static double mouseY = 0;

  // queue of typed key characters
  private static LinkedList<Character> keysTyped = new LinkedList<>();

  // set of key codes currently pressed down
  private static TreeSet<Integer> keysDown = new TreeSet<>();


  // singleton pattern: client can't instantiate
  private StdDraw() { }


  // static initializer
  static { init(); }

  /**
   * Set the window size to the default size 512-by-512 pixels.
   */
  public static void setCanvasSize() {
    setCanvasSize(DEFAULT_SIZE, DEFAULT_SIZE);
  }

  /**
   * Set the window size to w-by-h pixels.
   *
   * @param w the width as a number of pixels
   * @param h the height as a number of pixels
   * @throws java.lang.RuntimeException if the width or height is 0 or negative
   */
  public static void setCanvasSize(int w, int h) {
    if (w < 1 || h < 1) throw new RuntimeException("width and height must be positive");
    width = w;
    height = h;
    init();
  }

  // init
  private static void init() {
    if (frame != null) frame.setVisible(false);
    frame = new JFrame();
    offscreenImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    onscreenImage  = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    offscreen = offscreenImage.createGraphics();
    onscreen  = onscreenImage.createGraphics();
    setXscale();
    setYscale();
    offscreen.setColor(DEFAULT_CLEAR_COLOR);
    offscreen.fillRect(0, 0, width, height);
    setPenColor();
    setPenRadius();
    setFont();
    clear();

    // add antialiasing
    RenderingHints hints = new RenderingHints(RenderingHints.KEY_ANTIALIASING,
        RenderingHints.VALUE_ANTIALIAS_ON);
    hints.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
    offscreen.addRenderingHints(hints);

    // frame stuff
    ImageIcon icon = new ImageIcon(onscreenImage);
    JLabel draw = new JLabel(icon);

    draw.addMouseListener(std);
    draw.addMouseMotionListener(std);

    frame.setContentPane(draw);
    frame.addKeyListener(std);    // JLabel cannot get keyboard focus
    frame.setResizable(false);
    frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);    // closes all windows
    //frame.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); // closes only current window
    frame.setTitle("Standard Draw");
    frame.setJMenuBar(createMenuBar());
    frame.pack();
    frame.requestFocusInWindow();
    frame.setVisible(true);
  }

  // create the menu bar (changed to private)
  private static JMenuBar createMenuBar() {
    JMenuBar menuBar = new JMenuBar();
    JMenu menu = new JMenu("File");
    menuBar.add(menu);
    JMenuItem menuItem1 = new JMenuItem(" Save...   ");
    menuItem1.addActionListener(std);
    menuItem1.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S,
        Toolkit.getDefaultToolkit().getMenuShortcutKeyMask()));
    menu.add(menuItem1);
    return menuBar;
  }


  /* ***********************************************************************
   *  User and screen coordinate systems
   *************************************************************************/

  /**
   * Set the x-scale to be the default (between 0.0 and 1.0).
   */
  public static void setXscale() { setXscale(DEFAULT_XMIN, DEFAULT_XMAX); }

  /**
   * Set the y-scale to be the default (between 0.0 and 1.0).
   */
  public static void setYscale() { setYscale(DEFAULT_YMIN, DEFAULT_YMAX); }

  /**
   * Set the x-scale (a 10% border is added to the values)
   * @param min the minimum value of the x-scale
   * @param max the maximum value of the x-scale
   */
  public static void setXscale(double min, double max) {
    double size = max - min;
    synchronized (mouseLock) {
      xmin = min - BORDER * size;
      xmax = max + BORDER * size;
    }
  }

  /**
   * Set the y-scale (a 10% border is added to the values).
   * @param min the minimum value of the y-scale
   * @param max the maximum value of the y-scale
   */
  public static void setYscale(double min, double max) {
    double size = max - min;
    synchronized (mouseLock) {
      ymin = min - BORDER * size;
      ymax = max + BORDER * size;
    }
  }

  /**
   * Set the x-scale and y-scale (a 10% border is added to the values)
   * @param min the minimum value of the x- and y-scales
   * @param max the maximum value of the x- and y-scales
   */
  public static void setScale(double min, double max) {
    double size = max - min;
    synchronized (mouseLock) {
      xmin = min - BORDER * size;
      xmax = max + BORDER * size;
      ymin = min - BORDER * size;
      ymax = max + BORDER * size;
    }
  }

  // helper functions that scale from user coordinates to screen coordinates and back
  private static double  scaleX(double x) { return width  * (x - xmin) / (xmax - xmin); }
  private static double  scaleY(double y) { return height * (ymax - y) / (ymax - ymin); }
  private static double factorX(double w) { return w * width  / Math.abs(xmax - xmin);  }
  private static double factorY(double h) { return h * height / Math.abs(ymax - ymin);  }
  private static double   userX(double x) { return xmin + x * (xmax - xmin) / width;    }
  private static double   userY(double y) { return ymax - y * (ymax - ymin) / height;   }


  /**
   * Clear the screen to the default color (white).
   */
  public static void clear() { clear(DEFAULT_CLEAR_COLOR); }
  /**
   * Clear the screen to the given color.
   * @param color the Color to make the background
   */
  public static void clear(Color color) {
    offscreen.setColor(color);
    offscreen.fillRect(0, 0, width, height);
    offscreen.setColor(penColor);
    draw();
  }

  /**
   * Get the current pen radius.
   */
  public static double getPenRadius() { return penRadius; }

  /**
   * Set the pen size to the default (.002).
   */
  public static void setPenRadius() { setPenRadius(DEFAULT_PEN_RADIUS); }
  /**
   * Set the radius of the pen to the given size.
   * @param r the radius of the pen
   * @throws java.lang.RuntimeException if r is negative
   */
  public static void setPenRadius(double r) {
    if (r < 0) throw new RuntimeException("pen radius must be positive");
    penRadius = r;
    float scaledPenRadius = (float) (r * DEFAULT_SIZE);
    BasicStroke stroke = new BasicStroke(scaledPenRadius, BasicStroke.CAP_ROUND, BasicStroke.JOIN_ROUND);
    // BasicStroke stroke = new BasicStroke(scaledPenRadius);
    offscreen.setStroke(stroke);
  }

  /**
   * Get the current pen color.
   */
  public static Color getPenColor() { return penColor; }

  /**
   * Set the pen color to the default color (black).
   */
  public static void setPenColor() { setPenColor(DEFAULT_PEN_COLOR); }
  /**
   * Set the pen color to the given color. The available pen colors are
   * BLACK, BLUE, CYAN, DARK_GRAY, GRAY, GREEN, LIGHT_GRAY, MAGENTA,
   * ORANGE, PINK, RED, WHITE, and YELLOW.
   * @param color the Color to make the pen
   */
  public static void setPenColor(Color color) {
    penColor = color;
    offscreen.setColor(penColor);
  }

  /**
   * Get the current font.
   */
  public static Font getFont() { return font; }

  /**
   * Set the font to the default font (sans serif, 16 point).
   */
  public static void setFont() { setFont(DEFAULT_FONT); }

  /**
   * Set the font to the given value.
   * @param f the font to make text
   */
  public static void setFont(Font f) { font = f; }


  /* ***********************************************************************
   *  Drawing geometric shapes.
   *************************************************************************/

  /**
   * Draw a line from (x0, y0) to (x1, y1).
   * @param x0 the x-coordinate of the starting point
   * @param y0 the y-coordinate of the starting point
   * @param x1 the x-coordinate of the destination point
   * @param y1 the y-coordinate of the destination point
   */
  public static void line(double x0, double y0, double x1, double y1) {
    offscreen.draw(new Line2D.Double(scaleX(x0), scaleY(y0), scaleX(x1), scaleY(y1)));
    draw();
  }

  /**
   * Draw one pixel at (x, y).
   * @param x the x-coordinate of the pixel
   * @param y the y-coordinate of the pixel
   */
  private static void pixel(double x, double y) {
    offscreen.fillRect((int) Math.round(scaleX(x)), (int) Math.round(scaleY(y)), 1, 1);
  }

  /**
   * Draw a point at (x, y).
   * @param x the x-coordinate of the point
   * @param y the y-coordinate of the point
   */
  public static void point(double x, double y) {
    double xs = scaleX(x);
    double ys = scaleY(y);
    double r = penRadius;
    float scaledPenRadius = (float) (r * DEFAULT_SIZE);

    // double ws = factorX(2*r);
    // double hs = factorY(2*r);
    // if (ws <= 1 && hs <= 1) pixel(x, y);
    if (scaledPenRadius <= 1) pixel(x, y);
    else offscreen.fill(new Ellipse2D.Double(xs - scaledPenRadius/2, ys - scaledPenRadius/2,
        scaledPenRadius, scaledPenRadius));
    draw();
  }

  /**
   * Draw a circle of radius r, centered on (x, y).
   * @param x the x-coordinate of the center of the circle
   * @param y the y-coordinate of the center of the circle
   * @param r the radius of the circle
   * @throws java.lang.RuntimeException if the radius of the circle is negative
   */
  public static void circle(double x, double y, double r) {
    if (r < 0) throw new RuntimeException("circle radius can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*r);
    double hs = factorY(2*r);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.draw(new Ellipse2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }

  /**
   * Draw filled circle of radius r, centered on (x, y).
   * @param x the x-coordinate of the center of the circle
   * @param y the y-coordinate of the center of the circle
   * @param r the radius of the circle
   * @throws java.lang.RuntimeException if the radius of the circle is negative
   */
  public static void filledCircle(double x, double y, double r) {
    if (r < 0) throw new RuntimeException("circle radius can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*r);
    double hs = factorY(2*r);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.fill(new Ellipse2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }


  /**
   * Draw an ellipse with given semimajor and semiminor axes, centered on (x, y).
   * @param x the x-coordinate of the center of the ellipse
   * @param y the y-coordinate of the center of the ellipse
   * @param semiMajorAxis is the semimajor axis of the ellipse
   * @param semiMinorAxis is the semiminor axis of the ellipse
   * @throws java.lang.RuntimeException if either of the axes are negative
   */
  public static void ellipse(double x, double y, double semiMajorAxis, double semiMinorAxis) {
    if (semiMajorAxis < 0) throw new RuntimeException("ellipse semimajor axis can't be negative");
    if (semiMinorAxis < 0) throw new RuntimeException("ellipse semiminor axis can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*semiMajorAxis);
    double hs = factorY(2*semiMinorAxis);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.draw(new Ellipse2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }

  /**
   * Draw an ellipse with given semimajor and semiminor axes, centered on (x, y).
   * @param x the x-coordinate of the center of the ellipse
   * @param y the y-coordinate of the center of the ellipse
   * @param semiMajorAxis is the semimajor axis of the ellipse
   * @param semiMinorAxis is the semiminor axis of the ellipse
   * @throws java.lang.RuntimeException if either of the axes are negative
   */
  public static void filledEllipse(double x, double y, double semiMajorAxis, double semiMinorAxis) {
    if (semiMajorAxis < 0) throw new RuntimeException("ellipse semimajor axis can't be negative");
    if (semiMinorAxis < 0) throw new RuntimeException("ellipse semiminor axis can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*semiMajorAxis);
    double hs = factorY(2*semiMinorAxis);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.fill(new Ellipse2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }


  /**
   * Draw an arc of radius r, centered on (x, y), from angle1 to angle2 (in degrees).
   * @param x the x-coordinate of the center of the circle
   * @param y the y-coordinate of the center of the circle
   * @param r the radius of the circle
   * @param angle1 the starting angle. 0 would mean an arc beginning at 3 o'clock.
   * @param angle2 the angle at the end of the arc. For example, if
   *        you want a 90 degree arc, then angle2 should be angle1 + 90.
   * @throws java.lang.RuntimeException if the radius of the circle is negative
   */
  public static void arc(double x, double y, double r, double angle1, double angle2) {
    if (r < 0) throw new RuntimeException("arc radius can't be negative");
    while (angle2 < angle1) angle2 += 360;
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*r);
    double hs = factorY(2*r);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.draw(new Arc2D.Double(xs - ws/2, ys - hs/2, ws, hs, angle1, angle2 - angle1, Arc2D.OPEN));
    draw();
  }

  /**
   * Draw a square of side length 2r, centered on (x, y).
   * @param x the x-coordinate of the center of the square
   * @param y the y-coordinate of the center of the square
   * @param r radius is half the length of any side of the square
   * @throws java.lang.RuntimeException if r is negative
   */
  public static void square(double x, double y, double r) {
    if (r < 0) throw new RuntimeException("square side length can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*r);
    double hs = factorY(2*r);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.draw(new Rectangle2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }

  /**
   * Draw a filled square of side length 2r, centered on (x, y).
   * @param x the x-coordinate of the center of the square
   * @param y the y-coordinate of the center of the square
   * @param r radius is half the length of any side of the square
   * @throws java.lang.RuntimeException if r is negative
   */
  public static void filledSquare(double x, double y, double r) {
    if (r < 0) throw new RuntimeException("square side length can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*r);
    double hs = factorY(2*r);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.fill(new Rectangle2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }


  /**
   * Draw a rectangle of given half width and half height, centered on (x, y).
   * @param x the x-coordinate of the center of the rectangle
   * @param y the y-coordinate of the center of the rectangle
   * @param halfWidth is half the width of the rectangle
   * @param halfHeight is half the height of the rectangle
   * @throws java.lang.RuntimeException if halfWidth or halfHeight is negative
   */
  public static void rectangle(double x, double y, double halfWidth, double halfHeight) {
    if (halfWidth  < 0) throw new RuntimeException("half width can't be negative");
    if (halfHeight < 0) throw new RuntimeException("half height can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*halfWidth);
    double hs = factorY(2*halfHeight);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.draw(new Rectangle2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }

  /**
   * Draw a filled rectangle of given half width and half height, centered on (x, y).
   * @param x the x-coordinate of the center of the rectangle
   * @param y the y-coordinate of the center of the rectangle
   * @param halfWidth is half the width of the rectangle
   * @param halfHeight is half the height of the rectangle
   * @throws java.lang.RuntimeException if halfWidth or halfHeight is negative
   */
  public static void filledRectangle(double x, double y, double halfWidth, double halfHeight) {
    if (halfWidth  < 0) throw new RuntimeException("half width can't be negative");
    if (halfHeight < 0) throw new RuntimeException("half height can't be negative");
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(2*halfWidth);
    double hs = factorY(2*halfHeight);
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else offscreen.fill(new Rectangle2D.Double(xs - ws/2, ys - hs/2, ws, hs));
    draw();
  }


  /**
   * Draw a polygon with the given (x[i], y[i]) coordinates.
   * @param x an array of all the x-coordindates of the polygon
   * @param y an array of all the y-coordindates of the polygon
   */
  public static void polygon(double[] x, double[] y) {
    int N = x.length;
    GeneralPath path = new GeneralPath();
    path.moveTo((float) scaleX(x[0]), (float) scaleY(y[0]));
    for (int i = 0; i < N; i++)
      path.lineTo((float) scaleX(x[i]), (float) scaleY(y[i]));
    path.closePath();
    offscreen.draw(path);
    draw();
  }

  /**
   * Draw a filled polygon with the given (x[i], y[i]) coordinates.
   * @param x an array of all the x-coordindates of the polygon
   * @param y an array of all the y-coordindates of the polygon
   */
  public static void filledPolygon(double[] x, double[] y) {
    int N = x.length;
    GeneralPath path = new GeneralPath();
    path.moveTo((float) scaleX(x[0]), (float) scaleY(y[0]));
    for (int i = 0; i < N; i++)
      path.lineTo((float) scaleX(x[i]), (float) scaleY(y[i]));
    path.closePath();
    offscreen.fill(path);
    draw();
  }



  /* ***********************************************************************
   *  Drawing images.
   *************************************************************************/

  // get an image from the given filename
  private static Image getImage(String filename) {

    // to read from file
    ImageIcon icon = new ImageIcon(filename);

    // try to read from URL
    if ((icon == null) || (icon.getImageLoadStatus() != MediaTracker.COMPLETE)) {
      try {
              URL url = new java.net.URI(filename).toURL();
        icon = new ImageIcon(url);
      } catch (Exception e) { /* not a url */ }
    }

    // in case file is inside a .jar
    if ((icon == null) || (icon.getImageLoadStatus() != MediaTracker.COMPLETE)) {
      URL url = StdDraw.class.getResource(filename);
      if (url == null) throw new RuntimeException("image " + filename + " not found");
      icon = new ImageIcon(url);
    }

    return icon.getImage();
  }

  /**
   * Draw picture (gif, jpg, or png) centered on (x, y).
   * @param x the center x-coordinate of the image
   * @param y the center y-coordinate of the image
   * @param s the name of the image/picture, e.g., "ball.gif"
   * @throws java.lang.RuntimeException if the image is corrupt
   */
  public static void picture(double x, double y, String s) {
    Image image = getImage(s);
    double xs = scaleX(x);
    double ys = scaleY(y);
    int ws = image.getWidth(null);
    int hs = image.getHeight(null);
    if (ws < 0 || hs < 0) throw new RuntimeException("image " + s + " is corrupt");

    offscreen.drawImage(image, (int) Math.round(xs - ws/2.0), (int) Math.round(ys - hs/2.0), null);
    draw();
  }

  /**
   * Draw picture (gif, jpg, or png) centered on (x, y),
   * rotated given number of degrees
   * @param x the center x-coordinate of the image
   * @param y the center y-coordinate of the image
   * @param s the name of the image/picture, e.g., "ball.gif"
   * @param degrees is the number of degrees to rotate counterclockwise
   * @throws java.lang.RuntimeException if the image is corrupt
   */
  public static void picture(double x, double y, String s, double degrees) {
    Image image = getImage(s);
    double xs = scaleX(x);
    double ys = scaleY(y);
    int ws = image.getWidth(null);
    int hs = image.getHeight(null);
    if (ws < 0 || hs < 0) throw new RuntimeException("image " + s + " is corrupt");

    offscreen.rotate(Math.toRadians(-degrees), xs, ys);
    offscreen.drawImage(image, (int) Math.round(xs - ws/2.0), (int) Math.round(ys - hs/2.0), null);
    offscreen.rotate(Math.toRadians(+degrees), xs, ys);

    draw();
  }

  /**
   * Draw picture (gif, jpg, or png) centered on (x, y), rescaled to w-by-h.
   * @param x the center x coordinate of the image
   * @param y the center y coordinate of the image
   * @param s the name of the image/picture, e.g., "ball.gif"
   * @param w the width of the image
   * @param h the height of the image
   * @throws java.lang.RuntimeException if the width height are negative
   * @throws java.lang.RuntimeException if the image is corrupt
   */
  public static void picture(double x, double y, String s, double w, double h) {
    Image image = getImage(s);
    double xs = scaleX(x);
    double ys = scaleY(y);
    if (w < 0) throw new RuntimeException("width is negative: " + w);
    if (h < 0) throw new RuntimeException("height is negative: " + h);
    double ws = factorX(w);
    double hs = factorY(h);
    if (ws < 0 || hs < 0) throw new RuntimeException("image " + s + " is corrupt");
    if (ws <= 1 && hs <= 1) pixel(x, y);
    else {
      offscreen.drawImage(image, (int) Math.round(xs - ws/2.0),
          (int) Math.round(ys - hs/2.0),
          (int) Math.round(ws),
          (int) Math.round(hs), null);
    }
    draw();
  }


  /**
   * Draw picture (gif, jpg, or png) centered on (x, y), rotated
   * given number of degrees, rescaled to w-by-h.
   * @param x the center x-coordinate of the image
   * @param y the center y-coordinate of the image
   * @param s the name of the image/picture, e.g., "ball.gif"
   * @param w the width of the image
   * @param h the height of the image
   * @param degrees is the number of degrees to rotate counterclockwise
   * @throws java.lang.RuntimeException if the image is corrupt
   */
  public static void picture(double x, double y, String s, double w, double h, double degrees) {
    Image image = getImage(s);
    double xs = scaleX(x);
    double ys = scaleY(y);
    double ws = factorX(w);
    double hs = factorY(h);
    if (ws < 0 || hs < 0) throw new RuntimeException("image " + s + " is corrupt");
    if (ws <= 1 && hs <= 1) pixel(x, y);

    offscreen.rotate(Math.toRadians(-degrees), xs, ys);
    offscreen.drawImage(image, (int) Math.round(xs - ws/2.0),
        (int) Math.round(ys - hs/2.0),
        (int) Math.round(ws),
        (int) Math.round(hs), null);
    offscreen.rotate(Math.toRadians(+degrees), xs, ys);

    draw();
  }


  /* ***********************************************************************
   *  Drawing text.
   *************************************************************************/

  /**
   * Write the given text string in the current font, centered on (x, y).
   * @param x the center x-coordinate of the text
   * @param y the center y-coordinate of the text
   * @param s the text
   */
  public static void text(double x, double y, String s) {
    offscreen.setFont(font);
    FontMetrics metrics = offscreen.getFontMetrics();
    double xs = scaleX(x);
    double ys = scaleY(y);
    int ws = metrics.stringWidth(s);
    int hs = metrics.getDescent();
    offscreen.drawString(s, (float) (xs - ws/2.0), (float) (ys + hs));
    draw();
  }

  /**
   * Write the given text string in the current font, centered on (x, y) and
   * rotated by the specified number of degrees
   * @param x the center x-coordinate of the text
   * @param y the center y-coordinate of the text
   * @param s the text
   * @param degrees is the number of degrees to rotate counterclockwise
   */
  public static void text(double x, double y, String s, double degrees) {
    double xs = scaleX(x);
    double ys = scaleY(y);
    offscreen.rotate(Math.toRadians(-degrees), xs, ys);
    text(x, y, s);
    offscreen.rotate(Math.toRadians(+degrees), xs, ys);
  }


  /**
   * Write the given text string in the current font, left-aligned at (x, y).
   * @param x the x-coordinate of the text
   * @param y the y-coordinate of the text
   * @param s the text
   */
  public static void textLeft(double x, double y, String s) {
    offscreen.setFont(font);
    FontMetrics metrics = offscreen.getFontMetrics();
    double xs = scaleX(x);
    double ys = scaleY(y);
    int hs = metrics.getDescent();
    offscreen.drawString(s, (float) (xs), (float) (ys + hs));
    draw();
  }

  /**
   * Write the given text string in the current font, right-aligned at (x, y).
   * @param x the x-coordinate of the text
   * @param y the y-coordinate of the text
   * @param s the text
   */
  public static void textRight(double x, double y, String s) {
    offscreen.setFont(font);
    FontMetrics metrics = offscreen.getFontMetrics();
    double xs = scaleX(x);
    double ys = scaleY(y);
    int ws = metrics.stringWidth(s);
    int hs = metrics.getDescent();
    offscreen.drawString(s, (float) (xs - ws), (float) (ys + hs));
    draw();
  }



  /**
   * Display on screen, pause for t milliseconds, and turn on
   * <em>animation mode</em>: subsequent calls to
   * drawing methods such as {@code line()}, {@code circle()}, and {@code square()}
   * will not be displayed on screen until the next call to {@code show()}.
   * This is useful for producing animations (clear the screen, draw a bunch of shapes,
   * display on screen for a fixed amount of time, and repeat). It also speeds up
   * drawing a huge number of shapes (call {@code show(0)} to defer drawing
   * on screen, draw the shapes, and call {@code show(0)} to display them all
   * on screen at once).
   * @param t number of milliseconds
   */
  public static void show(int t) {
    defer = false;
    draw();
    try { Thread.sleep(t); }
    catch (InterruptedException e) { System.out.println("Error sleeping"); }
    defer = true;
  }

  /**
   * Display on-screen and turn off animation mode:
   * subsequent calls to
   * drawing methods such as {@code line()}, {@code circle()}, and {@code square()}
   * will be displayed on screen when called. This is the default.
   */
  public static void show() {
    defer = false;
    draw();
  }

  // draw onscreen if defer is false
  private static void draw() {
    if (defer) return;
    onscreen.drawImage(offscreenImage, 0, 0, null);
    frame.repaint();
  }


  /* ***********************************************************************
   *  Save drawing to a file.
   *************************************************************************/

  /**
   * Save onscreen image to file - suffix must be png, jpg, or gif.
   * @param filename the name of the file with one of the required suffixes
   */
  public static void save(String filename) {
    File file = new File(filename);
    String suffix = filename.substring(filename.lastIndexOf('.') + 1);

    // png files
    if (suffix.toLowerCase().equals("png")) {
      try { ImageIO.write(onscreenImage, suffix, file); }
      catch (IOException e) { e.printStackTrace(); }
    }

    // need to change from ARGB to RGB for jpeg
    // reference: http://archives.java.sun.com/cgi-bin/wa?A2=ind0404&L=java2d-interest&D=0&P=2727
    else if (suffix.toLowerCase().equals("jpg")) {
      WritableRaster raster = onscreenImage.getRaster();
      WritableRaster newRaster;
      newRaster = raster.createWritableChild(0, 0, width, height, 0, 0, new int[] {0, 1, 2});
      DirectColorModel cm = (DirectColorModel) onscreenImage.getColorModel();
      DirectColorModel newCM = new DirectColorModel(cm.getPixelSize(),
          cm.getRedMask(),
          cm.getGreenMask(),
          cm.getBlueMask());
      BufferedImage rgbBuffer = new BufferedImage(newCM, newRaster, false,  null);
      try { ImageIO.write(rgbBuffer, suffix, file); }
      catch (IOException e) { e.printStackTrace(); }
    }

    else {
      System.out.println("Invalid image file type: " + suffix);
    }
  }


  /**
   * This method cannot be called directly.
   */
  public void actionPerformed(ActionEvent e) {
    FileDialog chooser = new FileDialog(StdDraw.frame, "Use a .png or .jpg extension", FileDialog.SAVE);
    chooser.setVisible(true);
    String filename = chooser.getFile();
    if (filename != null) {
      StdDraw.save(chooser.getDirectory() + File.separator + chooser.getFile());
    }
  }


  /* ***********************************************************************
   *  Mouse interactions.
   *************************************************************************/

  /**
   * Is the mouse being pressed?
   * @return true or false
   */
  public static boolean mousePressed() {
    synchronized (mouseLock) {
      return mousePressed;
    }
  }

  /**
   * What is the x-coordinate of the mouse?
   * @return the value of the x-coordinate of the mouse
   */
  public static double mouseX() {
    synchronized (mouseLock) {
      return mouseX;
    }
  }

  /**
   * What is the y-coordinate of the mouse?
   * @return the value of the y-coordinate of the mouse
   */
  public static double mouseY() {
    synchronized (mouseLock) {
      return mouseY;
    }
  }


  /**
   * This method cannot be called directly.
   */
  public void mouseClicked(MouseEvent e) { }

  /**
   * This method cannot be called directly.
   */
  public void mouseEntered(MouseEvent e) { }

  /**
   * This method cannot be called directly.
   */
  public void mouseExited(MouseEvent e) { }

  /**
   * This method cannot be called directly.
   */
  public void mousePressed(MouseEvent e) {
    synchronized (mouseLock) {
      mouseX = StdDraw.userX(e.getX());
      mouseY = StdDraw.userY(e.getY());
      mousePressed = true;
    }
  }

  /**
   * This method cannot be called directly.
   */
  public void mouseReleased(MouseEvent e) {
    synchronized (mouseLock) {
      mousePressed = false;
    }
  }

  /**
   * This method cannot be called directly.
   */
  public void mouseDragged(MouseEvent e)  {
    synchronized (mouseLock) {
      mouseX = StdDraw.userX(e.getX());
      mouseY = StdDraw.userY(e.getY());
    }
  }

  /**
   * This method cannot be called directly.
   */
  public void mouseMoved(MouseEvent e) {
    synchronized (mouseLock) {
      mouseX = StdDraw.userX(e.getX());
      mouseY = StdDraw.userY(e.getY());
    }
  }


  /* ***********************************************************************
   *  Keyboard interactions.
   *************************************************************************/

  /**
   * Has the user typed a key?
   * @return true if the user has typed a key, false otherwise
   */
  public static boolean hasNextKeyTyped() {
    synchronized (keyLock) {
      return !keysTyped.isEmpty();
    }
  }

  /**
   * What is the next key that was typed by the user? This method returns
   * a Unicode character corresponding to the key typed (such as 'a' or 'A').
   * It cannot identify action keys (such as F1
   * and arrow keys) or modifier keys (such as control).
   * @return the next Unicode key typed
   */
  public static char nextKeyTyped() {
    synchronized (keyLock) {
      return keysTyped.removeLast();
    }
  }

  /**
   * Is the keycode currently being pressed? This method takes as an argument
   * the keycode (corresponding to a physical key). It can handle action keys
   * (such as F1 and arrow keys) and modifier keys (such as shift and control).
   * See <a href = "http://download.oracle.com/javase/6/docs/api/java/awt/event/KeyEvent.html">KeyEvent.java</a>
   * for a description of key codes.
   * @return true if keycode is currently being pressed, false otherwise
   */
  public static boolean isKeyPressed(int keycode) {
    synchronized (keyLock) {
      return keysDown.contains(keycode);
    }
  }


  /**
   * This method cannot be called directly.
   */
  public void keyTyped(KeyEvent e) {
    synchronized (keyLock) {
      keysTyped.addFirst(e.getKeyChar());
    }
  }

  /**
   * This method cannot be called directly.
   */
  public void keyPressed(KeyEvent e) {
    synchronized (keyLock) {
      keysDown.add(e.getKeyCode());
    }
  }

  /**
   * This method cannot be called directly.
   */
  public void keyReleased(KeyEvent e) {
    synchronized (keyLock) {
      keysDown.remove(e.getKeyCode());
    }
  }




  /**
   * Test client.
   */
  public static void main(String[] args) {
    StdDraw.square(.2, .8, .1);
    StdDraw.filledSquare(.8, .8, .2);
    StdDraw.circle(.8, .2, .2);

    StdDraw.setPenColor(StdDraw.BOOK_RED);
    StdDraw.setPenRadius(.02);
    StdDraw.arc(.8, .2, .1, 200, 45);

    // draw a blue diamond
    StdDraw.setPenRadius();
    StdDraw.setPenColor(StdDraw.BOOK_BLUE);
    double[] x = { .1, .2, .3, .2 };
    double[] y = { .2, .3, .2, .1 };
    StdDraw.filledPolygon(x, y);

    // text
    StdDraw.setPenColor(StdDraw.BLACK);
    StdDraw.text(0.2, 0.5, "black text");
    StdDraw.setPenColor(StdDraw.WHITE);
    StdDraw.text(0.8, 0.8, "white text");
  }

}