Class Picture

Object

Picture

All Implemented Interfaces:

ActionListener, EventListener

public final class Picture
extends Object
implements ActionListener

This class provides methods for manipulating individual pixels of an image. The original image can be read from a .jpg, .gif, or .png file or the user can create a blank image of a given size. This class includes methods for displaying the image in a window on the screen or saving it to a file.

Pixel (x, y) is column x and row y. By default, the origin (0, 0) is upper left, which is a common convention in image processing. The method setOriginLowerLeft() change the origin to the lower left.

Constructor Summary

Constructors

Constructor and Description
Picture(File file) Initializes a picture by reading in a .png, .gif, or .jpg from a file.
Picture(int width, int height) Initializes a blank width-by-height picture, with width columns and height rows, where each pixel is black.
Picture(Picture picture) Initializes a new picture that is a deep copy of the argument picture.
Picture(String filename) Initializes a picture by reading from a file or URL.

Method Summary

Methods

Modifier and Type	Method and Description
void	actionPerformed(ActionEvent e) 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 color of pixel (col, row).
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.
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 name) Saves the picture to a file in a standard image format.
void	set(int col, int row, Color color) Sets the color of pixel (col, row) to given color.
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.
int	width() Returns the width of the picture.

Methods inherited from class Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Picture

public Picture(int width,
       int height)

Initializes a blank 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

Picture

public Picture(Picture picture)

Initializes a new picture that is a deep copy of the argument picture.

Parameters:

picture - the picture to copy

Picture

public Picture(String filename)

Initializes a picture by reading from a file or URL.

Parameters:

filename - the name of the file (.png, .gif, or .jpg) or URL.

Picture

public Picture(File file)

Initializes a picture by reading in a .png, .gif, or .jpg from a file.

Parameters:

file - the file

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.

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 color of pixel (col, row).

Parameters:

col - the column index

row - the row index

Returns:

the color 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 given color.

Parameters:

col - the column index

row - the row index

color - the color

Throws:

IndexOutOfBoundsException - unless both 0 ≤ col < width and 0 ≤ row < height

NullPointerException - if color is null

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

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 name)

Saves the picture to a file in a standard image format. The filetype must be .png or .jpg.

Parameters:

name - the name of the file

save

public void save(File file)

Saves the picture to a file in a PNG or JPEG image format.

Parameters:

file - the file

actionPerformed

public void actionPerformed(ActionEvent e)

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.