java.awt.image
Class ColorModel

java.lang.Object   
  java.awt.image.ColorModel

All Implemented Interfaces:

Transparency

Direct Known Subclasses:

ComponentColorModel , IndexColorModel , PackedColorModel

public abstract class ColorModel
extends Object   
implements Transparency   

The ColorModel abstract class encapsulates the methods for translating a pixel value to color components (for example, red, green, and blue) and an alpha component. In order to render an image to the screen, a printer, or another image, pixel values must be converted to color and alpha components. As arguments to or return values from methods of this class, pixels are represented as 32-bit ints or as arrays of primitive types. The number, order, and interpretation of color components for a ColorModel is specified by its ColorSpace. A ColorModel used with pixel data that does not include alpha information treats all pixels as opaque, which is an alpha value of 1.0.

This ColorModel class supports two representations of pixel values. A pixel value can be a single 32-bit int or an array of primitive types. The Java(tm) Platform 1.0 and 1.1 APIs represented pixels as single byte or single int values. For purposes of the ColorModel class, pixel value arguments were passed as ints. The Java(tm) 2 Platform API introduced additional classes for representing images. With BufferedImage or RenderedImage objects, based on Raster and SampleModel classes, pixel values might not be conveniently representable as a single int. Consequently, ColorModel now has methods that accept pixel values represented as arrays of primitive types. The primitive type used by a particular ColorModel object is called its transfer type.

ColorModel objects used with images for which pixel values are not conveniently representable as a single int throw an IllegalArgumentException when methods taking a single int pixel argument are called. Subclasses of ColorModel must specify the conditions under which this occurs. This does not occur with DirectColorModel or IndexColorModel objects.

Currently, the transfer types supported by the Java 2D(tm) API are DataBuffer.TYPE_BYTE, DataBuffer.TYPE_USHORT, DataBuffer.TYPE_INT, DataBuffer.TYPE_SHORT, DataBuffer.TYPE_FLOAT, and DataBuffer.TYPE_DOUBLE. Most rendering operations will perform much faster when using ColorModels and images based on the first three of these types. In addition, some image filtering operations are not supported for ColorModels and images based on the latter three types. The transfer type for a particular ColorModel object is specified when the object is created, either explicitly or by default. All subclasses of ColorModel must specify what the possible transfer types are and how the number of elements in the primitive arrays representing pixels is determined.

For BufferedImages, the transfer type of its Raster and of the Raster object's SampleModel (available from the getTransferType methods of these classes) must match that of the ColorModel. The number of elements in an array representing a pixel for the Raster and SampleModel (available from the getNumDataElements methods of these classes) must match that of the ColorModel.

The algorithm used to convert from pixel values to color and alpha components varies by subclass. For example, there is not necessarily a one-to-one correspondence between samples obtained from the SampleModel of a BufferedImage object's Raster and color/alpha components. Even when there is such a correspondence, the number of bits in a sample is not necessarily the same as the number of bits in the corresponding color/alpha component. Each subclass must specify how the translation from pixel values to color/alpha components is done.

Methods in the ColorModel class use two different representations of color and alpha components - a normalized form and an unnormalized form. In the normalized form, each component is a float value between some minimum and maximum values. For the alpha component, the minimum is 0.0 and the maximum is 1.0. For color components the minimum and maximum values for each component can be obtained from the ColorSpace object. These values will often be 0.0 and 1.0 (e.g. normalized component values for the default sRGB color space range from 0.0 to 1.0), but some color spaces have component values with different upper and lower limits. These limits can be obtained using the getMinValue and getMaxValue methods of the ColorSpace class. Normalized color component values are not premultiplied. All ColorModels must support the normalized form.

In the unnormalized form, each component is an unsigned integral value between 0 and 2ⁿ - 1, where n is the number of significant bits for a particular component. If pixel values for a particular ColorModel represent color samples premultiplied by the alpha sample, unnormalized color component values are also premultiplied. The unnormalized form is used only with instances of ColorModel whose ColorSpace has minimum component values of 0.0 for all components and maximum values of 1.0 for all components. The unnormalized form for color and alpha components can be a convenient representation for ColorModels whose normalized component values all lie between 0.0 and 1.0. In such cases the integral value 0 maps to 0.0 and the value 2ⁿ - 1 maps to 1.0. In other cases, such as when the normalized component values can be either negative or positive, the unnormalized form is not convenient. Such ColorModel objects throw an IllegalArgumentException when methods involving an unnormalized argument are called. Subclasses of ColorModel must specify the conditions under which this occurs.

See Also:

IndexColorModel , ComponentColorModel , PackedColorModel , DirectColorModel , Image , BufferedImage , RenderedImage , ColorSpace , SampleModel , Raster , DataBuffer

Field Summary

protected int	pixel_bits The total number of bits in the pixel.
protected int	transferType Data type of the array used to represent pixel values.

Fields inherited from interface java.awt.Transparency

BITMASK , OPAQUE , TRANSLUCENT

Constructor Summary

	ColorModel (int bits) Constructs a ColorModel that translates pixels of the specified number of bits to color/alpha components.
protected	ColorModel (int pixel_bits, int[] bits, ColorSpace cspace, boolean hasAlpha, boolean isAlphaPremultiplied, int transparency, int transferType) Constructs a ColorModel that translates pixel values to color/alpha components.

Method Summary

ColorModel	coerceData (WritableRaster raster, boolean isAlphaPremultiplied) Forces the raster data to match the state specified in the isAlphaPremultiplied variable, assuming the data is currently correctly described by this ColorModel.
SampleModel	createCompatibleSampleModel (int w, int h) Creates a SampleModel with the specified width and height that has a data layout compatible with this ColorModel.
WritableRaster	createCompatibleWritableRaster (int w, int h) Creates a WritableRaster with the specified width and height that has a data layout (SampleModel) compatible with this ColorModel.
boolean	equals (Object obj) Tests if the specified Object is an instance of ColorModel and if it equals this ColorModel.
void	finalize () Disposes of system resources associated with this ColorModel once this ColorModel is no longer referenced.
abstract int	getAlpha (int pixel) Returns the alpha component for the specified pixel, scaled from 0 to 255.
int	getAlpha (Object inData) Returns the alpha component for the specified pixel, scaled from 0 to 255.
WritableRaster	getAlphaRaster (WritableRaster raster) Returns a Raster representing the alpha channel of an image, extracted from the input Raster, provided that pixel values of this ColorModel represent color and alpha information as separate spatial bands (e.g.
abstract int	getBlue (int pixel) Returns the blue color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
int	getBlue (Object inData) Returns the blue color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
ColorSpace	getColorSpace () Returns the ColorSpace associated with this ColorModel.
int[]	getComponents (int pixel, int[] components, int offset) Returns an array of unnormalized color/alpha components given a pixel in this ColorModel.
int[]	getComponents (Object pixel, int[] components, int offset) Returns an array of unnormalized color/alpha components given a pixel in this ColorModel.
int[]	getComponentSize () Returns an array of the number of bits per color/alpha component.
int	getComponentSize (int componentIdx) Returns the number of bits for the specified color/alpha component.
int	getDataElement (float[] normComponents, int normOffset) Returns a pixel value represented as an int in this ColorModel, given an array of normalized color/alpha components.
int	getDataElement (int[] components, int offset) Returns a pixel value represented as an int in this ColorModel, given an array of unnormalized color/alpha components.
Object	getDataElements (float[] normComponents, int normOffset, Object obj) Returns a data element array representation of a pixel in this ColorModel, given an array of normalized color/alpha components.
Object	getDataElements (int[] components, int offset, Object obj) Returns a data element array representation of a pixel in this ColorModel, given an array of unnormalized color/alpha components.
Object	getDataElements (int rgb, Object pixel) Returns a data element array representation of a pixel in this ColorModel, given an integer pixel representation in the default RGB color model.
abstract int	getGreen (int pixel) Returns the green color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
int	getGreen (Object inData) Returns the green color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
float[]	getNormalizedComponents (int[] components, int offset, float[] normComponents, int normOffset) Returns an array of all of the color/alpha components in normalized form, given an unnormalized component array.
float[]	getNormalizedComponents (Object pixel, float[] normComponents, int normOffset) Returns an array of all of the color/alpha components in normalized form, given a pixel in this ColorModel.
int	getNumColorComponents () Returns the number of color components in this ColorModel.
int	getNumComponents () Returns the number of components, including alpha, in this ColorModel.
int	getPixelSize () Returns the number of bits per pixel described by this ColorModel.
abstract int	getRed (int pixel) Returns the red color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
int	getRed (Object inData) Returns the red color component for the specified pixel, scaled from 0 to 255 in the default RGB ColorSpace, sRGB.
int	getRGB (int pixel) Returns the color/alpha components of the pixel in the default RGB color model format.
int	getRGB (Object inData) Returns the color/alpha components for the specified pixel in the default RGB color model format.
static ColorModel	getRGBdefault () Returns a DirectColorModel that describes the default format for integer RGB values used in many of the methods in the AWT image interfaces for the convenience of the programmer.
int	getTransferType () Returns the transfer type of this ColorModel.
int	getTransparency () Returns the transparency.
int[]	getUnnormalizedComponents (float[] normComponents, int normOffset, int[] components, int offset) Returns an array of all of the color/alpha components in unnormalized form, given a normalized component array.
boolean	hasAlpha () Returns whether or not alpha is supported in this ColorModel.
int	hashCode () Returns the hash code for this ColorModel.
boolean	isAlphaPremultiplied () Returns whether or not the alpha has been premultiplied in the pixel values to be translated by this ColorModel.
boolean	isCompatibleRaster (Raster raster) Returns true if raster is compatible with this ColorModel and false if it is not.
boolean	isCompatibleSampleModel (SampleModel sm) Checks if the SampleModel is compatible with this ColorModel.
String	toString () Returns the String representation of the contents of this ColorModelobject.

Methods inherited from class java.lang.Object

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

Field Detail

pixel_bits

protected int pixel_bits

The total number of bits in the pixel.

transferType

protected int transferType

Data type of the array used to represent pixel values.

Constructor Detail

ColorModel

public ColorModel(int bits)

Constructs a ColorModel that translates pixels of the specified number of bits to color/alpha components. The color space is the default RGB ColorSpace, which is sRGB. Pixel values are assumed to include alpha information. If color and alpha information are represented in the pixel value as separate spatial bands, the color bands are assumed not to be premultiplied with the alpha value. The transparency type is java.awt.Transparency.TRANSLUCENT. The transfer type will be the smallest of DataBuffer.TYPE_BYTE, DataBuffer.TYPE_USHORT, or DataBuffer.TYPE_INT that can hold a single pixel (or DataBuffer.TYPE_UNDEFINED if bits is greater than 32). Since this constructor has no information about the number of bits per color and alpha component, any subclass calling this constructor should override any method that requires this information.

Parameters:

bits - the number of bits of a pixel

Throws:

IllegalArgumentException - if the number of bits in bits is less than 1

ColorModel

protected ColorModel(int pixel_bits,
                     int[] bits,
                     ColorSpace    cspace,
                     boolean hasAlpha,
                     boolean isAlphaPremultiplied,
                     int transparency,
                     int transferType)

Constructs a ColorModel that translates pixel values to color/alpha components. Color components will be in the specified ColorSpace. pixel_bits is the number of bits in the pixel values. The bits array specifies the number of significant bits per color and alpha component. Its length should be the number of components in the ColorSpace if there is no alpha information in the pixel values, or one more than this number if there is alpha information. hasAlpha indicates whether or not alpha information is present. The boolean isAlphaPremultiplied specifies how to interpret pixel values in which color and alpha information are represented as separate spatial bands. If the boolean is true, color samples are assumed to have been multiplied by the alpha sample. The transparency specifies what alpha values can be represented by this color model. The transfer type is the type of primitive array used to represent pixel values. Note that the bits array contains the number of significant bits per color/alpha component after the translation from pixel values. For example, for an IndexColorModel with pixel_bits equal to 16, the bits array might have four elements with each element set to 8.

Parameters:

pixel_bits - the number of bits in the pixel values

bits - array that specifies the number of significant bits per color and alpha component

cspace - the specified ColorSpace

hasAlpha - true if alpha information is present; false otherwise

isAlphaPremultiplied - true if color samples are assumed to be premultiplied by the alpha samples; false otherwise

transparency - what alpha values can be represented by this color model

transferType - the type of the array used to represent pixel values

Throws:

IllegalArgumentException - if the length of the bit array is less than the number of color or alpha components in this ColorModel, or if the transparency is not a valid value.

IllegalArgumentException - if the sum of the number of bits in bits is less than 1 or if any of the elements in bits is less than 0.

See Also:

Transparency

Method Detail

getRGBdefault

public static ColorModel    getRGBdefault()

Returns a DirectColorModel that describes the default format for integer RGB values used in many of the methods in the AWT image interfaces for the convenience of the programmer. The color space is the default ColorSpace , sRGB. The format for the RGB values is an integer with 8 bits each of alpha, red, green, and blue color components ordered correspondingly from the most significant byte to the least significant byte, as in: 0xAARRGGBB. Color components are not premultiplied by the alpha component. This format does not necessarily represent the native or the most efficient ColorModel for a particular device or for all images. It is merely used as a common color model format.

Returns:

a DirectColorModelobject describing default RGB values.

hasAlpha

public final boolean hasAlpha()

Returns whether or not alpha is supported in this ColorModel.

Returns:

true if alpha is supported in this ColorModel; false otherwise.

isAlphaPremultiplied

public final boolean isAlphaPremultiplied()

Returns whether or not the alpha has been premultiplied in the pixel values to be translated by this ColorModel. If the boolean is true, this ColorModel is to be used to interpret pixel values in which color and alpha information are represented as separate spatial bands, and color samples are assumed to have been multiplied by the alpha sample.

Returns:

true if the alpha values are premultiplied in the pixel values to be translated by this ColorModel; false otherwise.

getTransferType

public final int getTransferType()

Returns the transfer type of this ColorModel. The transfer type is the type of primitive array used to represent pixel values as arrays.

Returns:

the transfer type.

getPixelSize

public int getPixelSize()

Returns the number of bits per pixel described by this ColorModel.

Returns:

the number of bits per pixel.

getComponentSize

public int getComponentSize(int componentIdx)

Returns the number of bits for the specified color/alpha component. Color components are indexed in the order specified by the ColorSpace. Typically, this order reflects the name of the color space type. For example, for TYPE_RGB, index 0 corresponds to red, index 1 to green, and index 2 to blue. If this ColorModel supports alpha, the alpha component corresponds to the index following the last color component.

Parameters:

componentIdx - the index of the color/alpha component

Returns:

the number of bits for the color/alpha component at the specified index.

Throws:

ArrayIndexOutOfBoundsException - if componentIdx is greater than the number of components or less than zero

NullPointerException - if the number of bits array is null

getComponentSize

public int[] getComponentSize()

Returns an array of the number of bits per color/alpha component. The array contains the color components in the order specified by the ColorSpace, followed by the alpha component, if present.

Returns:

an array of the number of bits per color/alpha component

getTransparency

public int getTransparency()

Returns the transparency. Returns either OPAQUE, BITMASK, or TRANSLUCENT.

Specified by:

getTransparency in interface Transparency

Returns:

the transparency of this ColorModel.

See Also:

Transparency.OPAQUE , Transparency.BITMASK , Transparency.TRANSLUCENT

getNumComponents

public int getNumComponents()

Returns the number of components, including alpha, in this ColorModel. This is equal to the number of color components, optionally plus one, if there is an alpha component.

Returns:

the number of components in this ColorModel

getNumColorComponents

public int getNumColorComponents()

Returns the number of color components in this ColorModel. This is the number of components returned by ColorSpace.getNumComponents() .

Returns:

the number of color components in this ColorModel.

See Also:

ColorSpace.getNumComponent