Object
- GrayscalePicture

All Implemented Interfaces:

ActionListener, EventListener
```
public final class GrayscalePicture
extends Object
implements ActionListener
```
The GrayscalePicture data type provides a basic capability for manipulating the individual pixels of a grayscale image. The original image can be read from a PNG, GIF, or 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 BufferedImage data type. The method setOriginLowerLeft() change the origin to the lower left.
The get() and set() methods use Color objects to get or set the color of the specified pixel. The Color objects are converted to grayscale if they have different values for the R, G, and B channels. The getGrayscale() and setGrayscale() methods use an 8-bit int to encode the grayscale value, thereby avoiding the need to create temporary 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 Picture for a version that supports 32-bit RGB color images.

Author:

Robert Sedgewick, Kevin Wayne

Constructor Summary

Constructors
Constructor	Description
`GrayscalePicture(int width, int height)`	Creates a `width`-by-`height` picture, with `width` columns and `height` rows, where each pixel is black.
`GrayscalePicture(GrayscalePicture picture)`	Creates a new grayscale picture that is a deep copy of the argument picture.
`GrayscalePicture(String filename)`	Creates a grayscale picture by reading an image from a file or URL.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`actionPerformed(ActionEvent event)`	Opens a save dialog box when the user selects "Save As" from the menu.
`boolean`	`equals(Object other)`	Returns true if this picture is equal to the argument picture.
`Color`	`get(int col, int row)`	Returns the grayscale value of pixel (`col`, `row`) as a `Color`.
`int`	`getGrayscale(int col, int row)`	Returns the grayscale value of pixel (`col`, `row`) as an `int` between 0 and 255.
`JLabel`	`getJLabel()`	Returns a `JLabel` containing this picture, for embedding in a `JPanel`, `JFrame` or other GUI widget.
`int`	`hashCode()`	This operation is not supported because pictures are mutable.
`int`	`height()`	Returns the height of the picture.
`void`	`hide()`	Hides the window on the screen.
`boolean`	`isVisible()`	Is the window containing the picture visible?
`static void`	`main(String[] args)`	Unit tests this `Picture` data type.
`void`	`save(File file)`	Saves the picture to a file in a PNG or JPEG image format.
`void`	`save(String filename)`	Saves the picture to a file in either PNG or JPEG format.
`void`	`set(int col, int row, Color color)`	Sets the color of pixel (`col`, `row`) to the given grayscale value.
`void`	`setGrayscale(int col, int row, int gray)`	Sets the color of pixel (`col`, `row`) to the given grayscale value between 0 and 255.
`void`	`setOriginLowerLeft()`	Sets the origin to be the lower left pixel.
`void`	`setOriginUpperLeft()`	Sets the origin to be the upper left pixel.
`void`	`show()`	Displays the picture in a window on the screen.
`String`	`toString()`	Returns a string representation of this picture.
`int`	`width()`	Returns the width of the picture.

Methods inherited from class java.lang.Object
clone, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - GrayscalePicture
```
public GrayscalePicture(int width,
                        int height)
```
    Creates a width-by-height picture, with width columns and height rows, where each pixel is black.
    
    Parameters:
    
    width - the width of the picture
    
    height - the height of the picture
    
    Throws:
    
    IllegalArgumentException - if width is negative
    
    IllegalArgumentException - if height is negative
  - GrayscalePicture
```
public GrayscalePicture(GrayscalePicture picture)
```
    Creates a new grayscale picture that is a deep copy of the argument picture.
    
    Parameters:
    
    picture - the picture to copy
    
    Throws:
    
    IllegalArgumentException - if picture is null
  - GrayscalePicture
```
public GrayscalePicture(String filename)
```
    Creates a grayscale picture by reading an image from a file or URL.
    
    Parameters:
    
    filename - the name of the file (.png, .gif, or .jpg) or URL.
    
    Throws:
    
    IllegalArgumentException - if filename is null
    
    IllegalArgumentException - if cannot read image from file or URL
- Method Detail
  - getJLabel
```
public JLabel getJLabel()
```
    Returns a JLabel containing this picture, for embedding in a JPanel, JFrame or other GUI widget.
    
    Returns:
    
    the JLabel
  - setOriginUpperLeft
```
public void setOriginUpperLeft()
```
    Sets the origin to be the upper left pixel. This is the default.
  - setOriginLowerLeft
```
public void setOriginLowerLeft()
```
    Sets the origin to be the lower left pixel.
  - show
```
public void show()
```
    Displays the picture in a window on the screen.
  - hide
```
public void hide()
```
    Hides the window on the screen.
  - isVisible
```
public boolean isVisible()
```
    Is the window containing the picture visible?
    
    Returns:
    
    true if the picture is visible, and false otherwise
  - height
```
public int height()
```
    Returns the height of the picture.
    
    Returns:
    
    the height of the picture (in pixels)
  - width
```
public int width()
```
    Returns the width of the picture.
    
    Returns:
    
    the width of the picture (in pixels)
  - get
```
public Color get(int col,
                 int row)
```
    Returns the grayscale value of pixel (col, row) as a Color.
    
    Parameters:
    
    col - the column index
    
    row - the row index
    
    Returns:
    
    the grayscale value of pixel (col, row)
    
    Throws:
    
    IndexOutOfBoundsException - unless both 0 <= col < width and 0 <= row < height
  - getGrayscale
```
public int getGrayscale(int col,
                        int row)
```
    Returns the grayscale value of pixel (col, row) as an int between 0 and 255. Using this method can be more efficient than get(int, int) because it does not create a Color object.
    
    Parameters:
    
    col - the column index
    
    row - the row index
    
    Returns:
    
    the 8-bit integer representation of the grayscale value of pixel (col, row)
    
    Throws:
    
    IndexOutOfBoundsException - unless both 0 <= col < width and 0 <= row < height
  - set
```
public void set(int col,
                int row,
                Color color)
```
    Sets the color of pixel (col, row) to the given grayscale value.
    
    Parameters:
    
    col - the column index
    
    row - the row index
    
    color - the color (converts to grayscale if color is not a shade of gray)
    
    Throws:
    
    IndexOutOfBoundsException - unless both 0 <= col < width and 0 <= row < height
    
    IllegalArgumentException - if color is null
  - setGrayscale
```
public void setGrayscale(int col,
                         int row,
                         int gray)
```
    Sets the color of pixel (col, row) to the given grayscale value between 0 and 255.
    
    Parameters:
    
    col - the column index
    
    row - the row index
    
    gray - the 8-bit integer representation of the grayscale value
    
    Throws:
    
    IndexOutOfBoundsException - unless both 0 <= col < width and 0 <= row < height
  - equals
```
public boolean equals(Object other)
```
    Returns true if this picture is equal to the argument picture.
    
    Overrides:
    
    equals in class Object
    
    Parameters:
    
    other - the other picture
    
    Returns:
    
    true if this picture is the same dimension as other and if all pixels have the same color; false otherwise
  - toString
```
public String toString()
```
    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.
    
    Overrides:
    
    toString in class Object
    
    Returns:
    
    a string representation of this picture
  - hashCode
```
public int hashCode()
```
    This operation is not supported because pictures are mutable.
    
    Overrides:
    
    hashCode in class Object
    
    Returns:
    
    does not return a value
    
    Throws:
    
    UnsupportedOperationException - if called
  - save
```
public void save(String filename)
```
    Saves the picture to a file in either PNG or JPEG format. The filetype extension must be either .png or .jpg.
    
    Parameters:
    
    filename - the name of the file
    
    Throws:
    
    IllegalArgumentException - if filename is null
    
    IllegalArgumentException - if filename is the empty string
    
    IllegalArgumentException - if filename has invalid filetype extension
    
    IllegalArgumentException - if cannot write the file filename
  - save
```
public void save(File file)
```
    Saves the picture to a file in a PNG or JPEG image format.
    
    Parameters:
    
    file - the file
    
    Throws:
    
    IllegalArgumentException - if file is null
  - actionPerformed
```
public void actionPerformed(ActionEvent event)
```
    Opens a save dialog box when the user selects "Save As" from the menu.
    
    Specified by:
    
    actionPerformed in interface ActionListener
  - main
```
public static void main(String[] args)
```
    Unit tests this Picture data type. Reads a picture specified by the command-line argument, and shows it in a window on the screen.
    
    Parameters:
    
    args - the command-line arguments

Class GrayscalePicture

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

GrayscalePicture

GrayscalePicture

GrayscalePicture

Method Detail

getJLabel

setOriginUpperLeft

setOriginLowerLeft

show

hide

isVisible

height

width

get

getGrayscale

set

setGrayscale

equals

toString

hashCode

save

save

actionPerformed

main