java.awt.image

Class IndexColorModel

java.lang.Object

java.awt.image.ColorModel

java.awt.image.IndexColorModel

All Implemented Interfaces:

Transparency

public class IndexColorModel
extends ColorModel

The IndexColorModel class is a ColorModel class that works with pixel values consisting of a single sample that is an index into a fixed colormap in the default sRGB color space. The colormap specifies red, green, blue, and optional alpha components corresponding to each index. All components are represented in the colormap as 8-bit unsigned integral values. Some constructors allow the caller to specify "holes" in the colormap by indicating which colormap entries are valid and which represent unusable colors via the bits set in a BigInteger object. This color model is similar to an X11 PseudoColor visual.

Some constructors provide a means to specify an alpha component for each pixel in the colormap, while others either provide no such means or, in some cases, a flag to indicate whether the colormap data contains alpha values. If no alpha is supplied to the constructor, an opaque alpha component (alpha = 1.0) is assumed for each entry. An optional transparent pixel value can be supplied that indicates a completely transparent pixel, regardless of any alpha component supplied or assumed for that pixel value. Note that the color components in the colormap of an IndexColorModel objects are never pre-multiplied with the alpha components.

The transparency of an IndexColorModel object is determined by examining the alpha components of the colors in the colormap and choosing the most specific value after considering the optional alpha values and any transparent index specified. The transparency value is Transparency.OPAQUE only if all valid colors in the colormap are opaque and there is no valid transparent pixel. If all valid colors in the colormap are either completely opaque (alpha = 1.0) or completely transparent (alpha = 0.0), which typically occurs when a valid transparent pixel is specified, the value is Transparency.BITMASK. Otherwise, the value is Transparency.TRANSLUCENT, indicating that some valid color has an alpha component that is neither completely transparent nor completely opaque (0.0 < alpha < 1.0).

The index represented by a pixel value is stored in the least significant n bits of the pixel representations passed to the methods of this class, where n is the pixel size specified to the constructor for a particular IndexColorModel object; n must be between 1 and 16, inclusive. Higher order bits in pixel representations are assumed to be zero. For those methods that use a primitive array pixel representation of type transferType, the array length is always one. The transfer types supported are DataBuffer.TYPE_BYTE and DataBuffer.TYPE_USHORT. A single int pixel representation is valid for all objects of this class, since it is always possible to represent pixel values used with this class in a single int. Therefore, methods that use this representation do not throw an IllegalArgumentException due to an invalid pixel value.

Many of the methods in this class are final. The reason for this is that the underlying native graphics code makes assumptions about the layout and operation of this class and those assumptions are reflected in the implementations of the methods here that are marked final. You can subclass this class for other reaons, but you cannot override or modify the behaviour of those methods.

Version:

10 Feb 1997

See Also:

ColorModel, ColorSpace, DataBuffer

Field Summary

Fields inherited from class java.awt.image.ColorModel

pixel_bits

Fields inherited from interface java.awt.Transparency

BITMASK, OPAQUE, TRANSLUCENT

Constructor Summary

Constructors

Constructor and Description
IndexColorModel(int bits, int size, byte[] r, byte[] g, byte[] b) Constructs an IndexColorModel from the specified arrays of red, green, and blue components.
IndexColorModel(int bits, int size, byte[] r, byte[] g, byte[] b, byte[] a) Constructs an IndexColorModel from the given arrays of red, green, blue and alpha components.
IndexColorModel(int bits, int size, byte[] r, byte[] g, byte[] b, int trans) Constructs an IndexColorModel from the given arrays of red, green, and blue components.
IndexColorModel(int bits, int size, byte[] cmap, int start, boolean hasalpha) Constructs an IndexColorModel from a single array of interleaved red, green, blue and optional alpha components.
IndexColorModel(int bits, int size, byte[] cmap, int start, boolean hasalpha, int trans) Constructs an IndexColorModel from a single array of interleaved red, green, blue and optional alpha components.

Method Summary

Methods

Modifier and Type	Method and Description
void	finalize() Disposes of system resources associated with this ColorModel once this ColorModel is no longer referenced.
int	getAlpha(int pixel) Returns the alpha component for the specified pixel, scaled from 0 to 255.
void	getAlphas(byte[] a) Copies the array of alpha transparency components into the specified array.
int	getBlue(int pixel) Returns the blue color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
void	getBlues(byte[] b) Copies the array of blue color components into the specified array.
int	getGreen(int pixel) Returns the green color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
void	getGreens(byte[] g) Copies the array of green color components into the specified array.
int	getMapSize() Returns the size of the color/alpha component arrays in this IndexColorModel.
int	getRed(int pixel) Returns the red color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
void	getReds(byte[] r) Copies the array of red color components into the specified array.
int	getRGB(int pixel) Returns the color/alpha components of the pixel in the default RGB color model format.
int	getTransparentPixel() Returns the index of the transparent pixel in this IndexColorModel or -1 if there is no transparent pixel.
String	toString() Returns the String representation of the contents of this ColorModelobject.

Methods inherited from class java.awt.image.ColorModel

equals, getColorSpace, getComponentSize, getComponentSize, getNumColorComponents, getNumComponents, getPixelSize, getRGBdefault, getTransferType, getTransparency, hasAlpha, hashCode, isAlphaPremultiplied

Methods inherited from class java.lang.Object

clone, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

IndexColorModel

public IndexColorModel(int bits,
               int size,
               byte[] r,
               byte[] g,
               byte[] b)

Constructs an IndexColorModel from the specified arrays of red, green, and blue components. Pixels described by this color model all have alpha components of 255 unnormalized (1.0 normalized), which means they are fully opaque. All of the arrays specifying the color components must have at least the specified number of entries. The ColorSpace is the default sRGB space. Since there is no alpha information in any of the arguments to this constructor, the transparency value is always Transparency.OPAQUE. The transfer type is the smallest of DataBuffer.TYPE_BYTE or DataBuffer.TYPE_USHORT that can hold a single pixel.

Parameters:

bits - the number of bits each pixel occupies

size - the size of the color component arrays

r - the array of red color components

g - the array of green color components

b - the array of blue color components

Throws:

IllegalArgumentException - if bits is less than 1 or greater than 16

IllegalArgumentException - if size is less than 1

IndexColorModel

public IndexColorModel(int bits,
               int size,
               byte[] r,
               byte[] g,
               byte[] b,
               int trans)

Constructs an IndexColorModel from the given arrays of red, green, and blue components. Pixels described by this color model all have alpha components of 255 unnormalized (1.0 normalized), which means they are fully opaque, except for the indicated transparent pixel. All of the arrays specifying the color components must have at least the specified number of entries. The ColorSpace is the default sRGB space. The transparency value may be Transparency.OPAQUE or Transparency.BITMASK depending on the arguments, as specified in the class description above. The transfer type is the smallest of DataBuffer.TYPE_BYTE or DataBuffer.TYPE_USHORT that can hold a single pixel.

Parameters:

bits - the number of bits each pixel occupies

size - the size of the color component arrays

r - the array of red color components

g - the array of green color components

b - the array of blue color components

trans - the index of the transparent pixel

Throws:

IllegalArgumentException - if bits is less than 1 or greater than 16

IllegalArgumentException - if size is less than 1

IndexColorModel

public IndexColorModel(int bits,
               int size,
               byte[] r,
               byte[] g,
               byte[] b,
               byte[] a)

Constructs an IndexColorModel from the given arrays of red, green, blue and alpha components. All of the arrays specifying the components must have at least the specified number of entries. The ColorSpace is the default sRGB space. The transparency value may be any of Transparency.OPAQUE, Transparency.BITMASK, or Transparency.TRANSLUCENT depending on the arguments, as specified in the class description above. The transfer type is the smallest of DataBuffer.TYPE_BYTE or DataBuffer.TYPE_USHORT that can hold a single pixel.

Parameters:

bits - the number of bits each pixel occupies

size - the size of the color component arrays

r - the array of red color components

g - the array of green color components

b - the array of blue color components

a - the array of alpha value components

Throws:

IllegalArgumentException - if bits is less than 1 or greater than 16

IllegalArgumentException - if size is less than 1

IndexColorModel

public IndexColorModel(int bits,
               int size,
               byte[] cmap,
               int start,
               boolean hasalpha)

Constructs an IndexColorModel from a single array of interleaved red, green, blue and optional alpha components. The array must have enough values in it to fill all of the needed component arrays of the specified size. The ColorSpace is the default sRGB space. The transparency value may be any of Transparency.OPAQUE, Transparency.BITMASK, or Transparency.TRANSLUCENT depending on the arguments, as specified in the class description above. The transfer type is the smallest of DataBuffer.TYPE_BYTE or DataBuffer.TYPE_USHORT that can hold a single pixel.

Parameters:

bits - the number of bits each pixel occupies

size - the size of the color component arrays

cmap - the array of color components

start - the starting offset of the first color component

hasalpha - indicates whether alpha values are contained in the cmap array

Throws:

IllegalArgumentException - if bits is less than 1 or greater than 16

IllegalArgumentException - if size is less than 1

IndexColorModel

public IndexColorModel(int bits,
               int size,
               byte[] cmap,
               int start,
               boolean hasalpha,
               int trans)

Constructs an IndexColorModel from a single array of interleaved red, green, blue and optional alpha components. The specified transparent index represents a pixel that is considered entirely transparent regardless of any alpha value specified for it. The array must have enough values in it to fill all of the needed component arrays of the specified size. The ColorSpace is the default sRGB space. The transparency value may be any of Transparency.OPAQUE, Transparency.BITMASK, or Transparency.TRANSLUCENT depending on the arguments, as specified in the class description above. The transfer type is the smallest of DataBuffer.TYPE_BYTE or DataBuffer.TYPE_USHORT that can hold a single pixel.

Parameters:

bits - the number of bits each pixel occupies

size - the size of the color component arrays

cmap - the array of color components

start - the starting offset of the first color component

hasalpha - indicates whether alpha values are contained in the cmap array

trans - the index of the fully transparent pixel

Throws:

IllegalArgumentException - if bits is less than 1 or greater than 16

IllegalArgumentException - if size is less than 1

Method Detail

getMapSize

public final int getMapSize()

Returns the size of the color/alpha component arrays in this IndexColorModel.

Returns:

the size of the color and alpha component arrays.

getTransparentPixel

public final int getTransparentPixel()

Returns the index of the transparent pixel in this IndexColorModel or -1 if there is no transparent pixel.

Returns:

the index of this IndexColorModel object's transparent pixel, or -1 if there is no such pixel.

getReds

public final void getReds(byte[] r)

Copies the array of red color components into the specified array. Only the initial entries of the array as specified by getMapSize are written.

Parameters:

r - the specified array into which the elements of the array of red color components are copied

getGreens

public final void getGreens(byte[] g)

Copies the array of green color components into the specified array. Only the initial entries of the array as specified by getMapSize are written.

Parameters:

g - the specified array into which the elements of the array of green color components are copied

getBlues

public final void getBlues(byte[] b)

Copies the array of blue color components into the specified array. Only the initial entries of the array as specified by getMapSize are written.

Parameters:

b - the specified array into which the elements of the array of blue color components are copied

getAlphas

public final void getAlphas(byte[] a)

Copies the array of alpha transparency components into the specified array. Only the initial entries of the array as specified by getMapSize are written.

Parameters:

a - the specified array into which the elements of the array of alpha components are copied

getRed

public final int getRed(int pixel)

Returns the red color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB. The pixel value is specified as an int. The returned value is a non pre-multiplied value.

Specified by:

getRed in class ColorModel

Parameters:

pixel - the specified pixel

Returns:

the value of the red color component for the specified pixel

getGreen

public final int getGreen(int pixel)

Returns the green color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB. The pixel value is specified as an int. The returned value is a non pre-multiplied value.

Specified by:

getGreen in class ColorModel

Parameters:

pixel - the specified pixel

Returns:

the value of the green color component for the specified pixel

getBlue

public final int getBlue(int pixel)

Returns the blue color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB. The pixel value is specified as an int. The returned value is a non pre-multiplied value.

Specified by:

getBlue in class ColorModel

Parameters:

pixel - the specified pixel

Returns:

the value of the blue color component for the specified pixel

getAlpha

public final int getAlpha(int pixel)

Returns the alpha component for the specified pixel, scaled from 0 to 255. The pixel value is specified as an int.

Specified by:

getAlpha in class ColorModel

Parameters:

pixel - the specified pixel

Returns:

the value of the alpha component for the specified pixel

getRGB

public final int getRGB(int pixel)

Returns the color/alpha components of the pixel in the default RGB color model format. The pixel value is specified as an int. The returned value is in a non pre-multiplied format.

Overrides:

getRGB in class ColorModel

Parameters:

pixel - the specified pixel

Returns:

the color and alpha components of the specified pixel

See Also:

ColorModel.getRGBdefault()

finalize

public void finalize()

Disposes of system resources associated with this ColorModel once this ColorModel is no longer referenced.

Overrides:

finalize in class ColorModel

toString

public String toString()

Returns the String representation of the contents of this ColorModelobject.

Overrides:

toString in class ColorModel

Returns:

a String representing the contents of this ColorModel object.