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)
        @SuppressWarnings("deprecation")
        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 URL(filename);
                                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");
        }

}