GrayscalePicture data type provides a basic capability
* for manipulating the individual pixels of a grayscale image.
* The original image can be read from a {@code PNG}, {@code GIF},
* or {@code JPEG} file or the user can create a blank image of a given dimension.
* This class includes methods for displaying the image in a window on
* the screen or saving it to a file.
* * Pixel (col, row) is column col and row row. * By default, the origin (0, 0) is the pixel in the top-left corner. * These are common conventions in image processing and consistent with Java's * {@link java.awt.image.BufferedImage} data type. * The method {@link #setOriginLowerLeft()} change the origin to the lower left. *
* The {@code get()} and {@code set()} methods use {@link Color} objects to get * or set the color of the specified pixel. The {@link Color} objects are converted * to grayscale if they have different values for the R, G, and B channels. * The {@code getGrayscale()} and {@code setGrayscale()} methods use an * 8-bit {@code int} to encode the grayscale value, thereby avoiding the need to * create temporary {@code Color} objects. *
* A W-by-H picture uses ~ 4 W H bytes of memory,
* since the color of each pixel is encoded as a 32-bit int
* (even though, in principle, only ~ W H bytes are needed).
*
* For additional documentation, see
* Section 3.1 of
* Computer Science: An Interdisciplinary Approach
* by Robert Sedgewick and Kevin Wayne.
* See {@link Picture} for a version that supports 32-bit RGB color images.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public final class GrayscalePicture implements ActionListener {
private BufferedImage image; // the rasterized image
private JFrame frame; // on-screen view
private String filename; // name of file
private boolean isOriginUpperLeft = true; // location of origin
private boolean isVisible = false; // is the frame visible?
private final int width, height; // width and height
/**
* Creates a {@code width}-by-{@code height} picture, with {@code width} columns
* and {@code height} rows, where each pixel is black.
*
* @param width the width of the picture
* @param height the height of the picture
* @throws IllegalArgumentException if {@code width} is negative
* @throws IllegalArgumentException if {@code height} is negative
*/
public GrayscalePicture(int width, int height) {
if (width < 0) throw new IllegalArgumentException("width must be non-negative");
if (height < 0) throw new IllegalArgumentException("height must be non-negative");
this.width = width;
this.height = height;
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
}
/**
* Creates a new grayscale picture that is a deep copy of the argument picture.
*
* @param picture the picture to copy
* @throws IllegalArgumentException if {@code picture} is {@code null}
*/
public GrayscalePicture(GrayscalePicture picture) {
if (picture == null) throw new IllegalArgumentException("constructor argument is null");
width = picture.width();
height = picture.height();
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
filename = picture.filename;
isOriginUpperLeft = picture.isOriginUpperLeft;
for (int col = 0; col < width(); col++)
for (int row = 0; row < height(); row++)
image.setRGB(col, row, picture.image.getRGB(col, row));
}
/**
* Creates a grayscale picture by reading an image from a file or URL.
*
* @param name the name of the file (.png, .gif, or .jpg) or URL.
* @throws IllegalArgumentException if cannot read image
* @throws IllegalArgumentException if {@code name} is {@code null}
*/
public GrayscalePicture(String name) {
if (name == null) throw new IllegalArgumentException("constructor argument is null");
this.filename = name;
try {
// try to read from file in working directory
File file = new File(name);
if (file.isFile()) {
image = ImageIO.read(file);
}
else {
// resource relative to .class file
URL url = getClass().getResource(name);
// resource relative to classloader root
if (url == null) {
url = getClass().getClassLoader().getResource(name);
}
// or URL from web
if (url == null) {
url = new URL(name);
}
image = ImageIO.read(url);
}
if (image == null) {
throw new IllegalArgumentException("could not read image: " + name);
}
width = image.getWidth(null);
height = image.getHeight(null);
// convert to grayscale in-place
for (int col = 0; col < width; col++) {
for (int row = 0; row < height; row++) {
Color color = new Color(image.getRGB(col, row));
Color gray = toGray(color);
image.setRGB(col, row, gray.getRGB());
}
}
}
catch (IOException ioe) {
throw new IllegalArgumentException("could not open image: " + name, ioe);
}
}
// Returns a grayscale version of the given color as a Color object.
private static Color toGray(Color color) {
int r = color.getRed();
int g = color.getGreen();
int b = color.getBlue();
int y = (int) (Math.round(0.299*r + 0.587*g + 0.114*b));
return new Color(y, y, y);
}
/**
* Returns a {@link JLabel} containing this picture, for embedding in a {@link JPanel},
* {@link JFrame} or other GUI widget.
*
* @return the {@code JLabel}
*/
public JLabel getJLabel() {
if (image == null) return null; // no image available
ImageIcon icon = new ImageIcon(image);
return new JLabel(icon);
}
/**
* Sets the origin to be the upper left pixel. This is the default.
*/
public void setOriginUpperLeft() {
isOriginUpperLeft = true;
}
/**
* Sets the origin to be the lower left pixel.
*/
public void setOriginLowerLeft() {
isOriginUpperLeft = false;
}
/**
* Displays the picture in a window on the screen.
*/
public void show() {
// create the GUI for viewing the image if needed
if (frame == null) {
frame = new JFrame();
JMenuBar menuBar = new JMenuBar();
JMenu menu = new JMenu("File");
menuBar.add(menu);
JMenuItem menuItem1 = new JMenuItem(" Save... ");
menuItem1.addActionListener(this);
// Java 11: use getMenuShortcutKeyMaskEx()
// Java 8: use getMenuShortcutKeyMask()
menuItem1.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_S,
Toolkit.getDefaultToolkit().getMenuShortcutKeyMaskEx()));
menu.add(menuItem1);
frame.setJMenuBar(menuBar);
frame.setContentPane(getJLabel());
// f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
if (filename == null) frame.setTitle(width + "-by-" + height);
else frame.setTitle(filename);
frame.setResizable(false);
frame.pack();
}
// draw
frame.setVisible(true);
isVisible = true;
frame.repaint();
}
/**
* Hides the window on the screen.
*/
public void hide() {
if (frame != null) {
isVisible = false;
frame.setVisible(false);
}
}
/**
* Is the window containing the picture visible?
* @return {@code true} if the picture is visible, and {@code false} otherwise
*/
public boolean isVisible() {
return isVisible;
}
/**
* Returns the height of the picture.
*
* @return the height of the picture (in pixels)
*/
public int height() {
return height;
}
/**
* Returns the width of the picture.
*
* @return the width of the picture (in pixels)
*/
public int width() {
return width;
}
private void validateRowIndex(int row) {
if (row < 0 || row >= height())
throw new IllegalArgumentException("row index must be between 0 and " + (height() - 1) + ": " + row);
}
private void validateColumnIndex(int col) {
if (col < 0 || col >= width())
throw new IllegalArgumentException("column index must be between 0 and " + (width() - 1) + ": " + col);
}
private void validateGrayscaleValue(int gray) {
if (gray < 0 || gray >= 256)
throw new IllegalArgumentException("grayscale value must be between 0 and 255");
}
/**
* Returns the grayscale value of pixel ({@code col}, {@code row}) as a {@link java.awt.Color}.
*
* @param col the column index
* @param row the row index
* @return the grayscale value of pixel ({@code col}, {@code row})
* @throws IllegalArgumentException unless both {@code 0 <= col < width} and {@code 0 <= row < height}
*/
public Color get(int col, int row) {
validateColumnIndex(col);
validateRowIndex(row);
Color color = new Color(image.getRGB(col, row));
return toGray(color);
}
/**
* Returns the grayscale value of pixel ({@code col}, {@code row}) as an {@code int}
* between 0 and 255.
* Using this method can be more efficient than {@link #get(int, int)} because
* it does not create a {@code Color} object.
*
* @param col the column index
* @param row the row index
* @return the 8-bit integer representation of the grayscale value of pixel ({@code col}, {@code row})
* @throws IllegalArgumentException unless both {@code 0 <= col < width} and {@code 0 <= row < height}
*/
public int getGrayscale(int col, int row) {
validateColumnIndex(col);
validateRowIndex(row);
if (isOriginUpperLeft) return image.getRGB(col, row) & 0xFF;
else return image.getRGB(col, height - row - 1) & 0xFF;
}
/**
* Sets the color of pixel ({@code col}, {@code row}) to the given grayscale value.
*
* @param col the column index
* @param row the row index
* @param color the color (converts to grayscale if color is not a shade of gray)
* @throws IllegalArgumentException unless both {@code 0 <= col < width} and {@code 0 <= row < height}
* @throws IllegalArgumentException if {@code color} is {@code null}
*/
public void set(int col, int row, Color color) {
validateColumnIndex(col);
validateRowIndex(row);
if (color == null) throw new IllegalArgumentException("color argument is null");
Color gray = toGray(color);
image.setRGB(col, row, gray.getRGB());
}
/**
* Sets the color of pixel ({@code col}, {@code row}) to the given grayscale value
* between 0 and 255.
*
* @param col the column index
* @param row the row index
* @param gray the 8-bit integer representation of the grayscale value
* @throws IllegalArgumentException unless both {@code 0 <= col < width} and {@code 0 <= row < height}
*/
public void setGrayscale(int col, int row, int gray) {
validateColumnIndex(col);
validateRowIndex(row);
validateGrayscaleValue(gray);
int rgb = gray | (gray << 8) | (gray << 16);
if (isOriginUpperLeft) image.setRGB(col, row, rgb);
else image.setRGB(col, height - row - 1, rgb);
}
/**
* Returns true if this picture is equal to the argument picture.
*
* @param other the other picture
* @return {@code true} if this picture is the same dimension as {@code other}
* and if all pixels have the same color; {@code false} otherwise
*/
public boolean equals(Object other) {
if (other == this) return true;
if (other == null) return false;
if (other.getClass() != this.getClass()) return false;
GrayscalePicture that = (GrayscalePicture) other;
if (this.width() != that.width()) return false;
if (this.height() != that.height()) return false;
for (int col = 0; col < width(); col++)
for (int row = 0; row < height(); row++)
if (this.getGrayscale(col, row) != that.getGrayscale(col, row)) return false;
return true;
}
/**
* Returns a string representation of this picture.
* The result is a width-by-height matrix of pixels,
* where the grayscale value of a pixel is an integer between 0 and 255.
*
* @return a string representation of this picture
*/
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append(width +"-by-" + height + " grayscale picture (grayscale values given in hex)\n");
for (int row = 0; row < height; row++) {
for (int col = 0; col < width; col++) {
int gray;
if (isOriginUpperLeft) gray = 0xFF & image.getRGB(col, row);
else gray = 0xFF & image.getRGB(col, height - row - 1);
sb.append(String.format("%3d ", gray));
}
sb.append("\n");
}
return sb.toString().trim();
}
/**
* This operation is not supported because pictures are mutable.
*
* @return does not return a value
* @throws UnsupportedOperationException if called
*/
public int hashCode() {
throw new UnsupportedOperationException("hashCode() is not supported because pictures are mutable");
}
/**
* Saves the picture to a file in either PNG or JPEG format.
* The filetype extension must be either .png or .jpg.
*
* @param name the name of the file
* @throws IllegalArgumentException if {@code name} is {@code null}
*/
public void save(String name) {
if (name == null) throw new IllegalArgumentException("argument to save() is null");
save(new File(name));
filename = name;
}
/**
* Saves the picture to a file in a PNG or JPEG image format.
*
* @param file the file
* @throws IllegalArgumentException if {@code file} is {@code null}
*/
public void save(File file) {
if (file == null) throw new IllegalArgumentException("argument to save() is null");
filename = file.getName();
if (frame != null) frame.setTitle(filename);
String suffix = filename.substring(filename.lastIndexOf('.') + 1);
if (!filename.contains(".") || suffix.length() == 0) {
System.out.printf("Error: the filename '%s' has no file extension, such as .jpg or .png\n", filename);
return;
}
if ("jpg".equalsIgnoreCase(suffix) || "png".equalsIgnoreCase(suffix)) {
try {
ImageIO.write(image, suffix, file);
}
catch (IOException e) {
e.printStackTrace();
}
}
else {
System.out.println("Error: filename must end in .jpg or .png");
}
}
/**
* Opens a save dialog box when the user selects "Save As" from the menu.
*/
@Override
public void actionPerformed(ActionEvent e) {
FileDialog chooser = new FileDialog(frame,
"Use a .png or .jpg extension", FileDialog.SAVE);
chooser.setVisible(true);
String selectedDirectory = chooser.getDirectory();
String selectedFilename = chooser.getFile();
if (selectedDirectory != null && selectedFilename != null) {
save(selectedDirectory + selectedFilename);
}
}
/**
* Unit tests this {@code Picture} data type.
* Reads a picture specified by the command-line argument,
* and shows it in a window on the screen.
*
* @param args the command-line arguments
*/
public static void main(String[] args) {
GrayscalePicture picture = new GrayscalePicture(args[0]);
StdOut.printf("%d-by-%d\n", picture.width(), picture.height());
GrayscalePicture copy = new GrayscalePicture(picture);
picture.show();
copy.show();
while (!StdIn.isEmpty()) {
int row = StdIn.readInt();
int col = StdIn.readInt();
int gray = StdIn.readInt();
picture.setGrayscale(row, col, gray);
StdOut.println(picture.get(row, col));
StdOut.println(picture.getGrayscale(row, col));
}
}
}
/******************************************************************************
* Copyright 2002-2022, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* algs4.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with algs4.jar. If not, see http://www.gnu.org/licenses.
******************************************************************************/