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");
	}

}