ColorModel (Java SE 12 & JDK 12 )
Keywords: java.awt.image.ColorModel class

Module java.desktop
Package 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

    Fields
    Modifier and Type | Field | Description
    --- | --- | ---
    `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 declared in interface java.awt.Transparency

      `BITMASK, OPAQUE, TRANSLUCENT`

  - ### Constructor Summary

    Constructors
    Modifier | Constructor | Description
    --- | --- | ---
    `` | `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

    Modifier and Type | Method | Description
    --- | --- | ---
    `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)` | This method simply delegates to the default implementation in `Object` which is identical to an `==` test since this class cannot enforce the issues of a proper equality test among multiple independent subclass branches.
    `void` | `finalize()` | Deprecated. The `finalize` method has been deprecated.
    `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()` | This method simply delegates to the default implementation in `Object` which returns the system ID for the class.
    `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 `ColorModel` object.

    - ### Methods declared in 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 `DirectColorModel` object 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.
      Since:
        1.3

    - #### 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.getNumComponents()`

    - #### getRed

          public 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. A color conversion is done if necessary. The pixel value is specified as an int. An `IllegalArgumentException` is thrown if pixel values for this `ColorModel` are not conveniently representable as a single int. The returned value is not a pre-multiplied value. For example, if the alpha is premultiplied, this method divides it out before returning the value. If the alpha value is 0, the red value is 0.
      Parameters:
        `pixel` - a specified pixel
      Returns:
        the value of the red component of the specified pixel.

    - #### getGreen

          public 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. A color conversion is done if necessary. The pixel value is specified as an int. An `IllegalArgumentException` is thrown if pixel values for this `ColorModel` are not conveniently representable as a single int. The returned value is a non pre-multiplied value. For example, if the alpha is premultiplied, this method divides it out before returning the value. If the alpha value is 0, the green value is 0.
      Parameters:
        `pixel` - the specified pixel
      Returns:
        the value of the green component of the specified pixel.

    - #### getBlue

          public 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. A color conversion is done if necessary. The pixel value is specified as an int. An `IllegalArgumentException` is thrown if pixel values for this `ColorModel` are not conveniently representable as a single int. The returned value is a non pre-multiplied value, for example, if the alpha is premultiplied, this method divides it out before returning the value. If the alpha value is 0, the blue value is 0.
      Parameters:
        `pixel` - the specified pixel
      Returns:
        the value of the blue component of the specified pixel.

    - #### getAlpha

          public abstract 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. An `IllegalArgumentException` is thrown if pixel values for this `ColorModel` are not conveniently representable as a single int.
      Parameters:
        `pixel` - the specified pixel
      Returns:
        the value of alpha component of the specified pixel.

    - #### getRGB

          public int getRGB​(int pixel)

      Returns the color/alpha components of the pixel in the default RGB color model format. A color conversion is done if necessary. The pixel value is specified as an int. An `IllegalArgumentException` thrown if pixel values for this `ColorModel` are not conveniently representable as a single int. The returned value is in a non pre-multiplied format. For example, if the alpha is premultiplied, this method divides it out of the color components. If the alpha value is 0, the color values are 0.
      Parameters:
        `pixel` - the specified pixel
      Returns:
        the RGB value of the color/alpha components of the specified pixel.
      See Also:
        `getRGBdefault()`

    - #### getRed

          public int getRed​(Object inData)

      Returns the red color component for the specified pixel, scaled from 0 to 255 in the default RGB `ColorSpace`, sRGB. A color conversion is done if necessary. The pixel value is specified by an array of data elements of type transferType passed in as an object reference. The returned value is a non pre-multiplied value. For example, if alpha is premultiplied, this method divides it out before returning the value. If the alpha value is 0, the red value is 0. If `inData` is not a primitive array of type transferType, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `inData` is not large enough to hold a pixel value for this `ColorModel`. If this `transferType` is not supported, a `UnsupportedOperationException` will be thrown. Since `ColorModel` is an abstract class, any instance must be an instance of a subclass. Subclasses inherit the implementation of this method and if they don't override it, this method throws an exception if the subclass uses a `transferType` other than `DataBuffer.TYPE_BYTE`, `DataBuffer.TYPE_USHORT`, or `DataBuffer.TYPE_INT`.
      Parameters:
        `inData` - an array of pixel values
      Returns:
        the value of the red component of the specified pixel.
      Throws:
        `ClassCastException` - if `inData` is not a primitive array of type `transferType`
        `ArrayIndexOutOfBoundsException` - if `inData` is not large enough to hold a pixel value for this `ColorModel`
        `UnsupportedOperationException` - if this `transferType` is not supported by this `ColorModel`

    - #### getGreen

          public int getGreen​(Object inData)

      Returns the green color component for the specified pixel, scaled from 0 to 255 in the default RGB `ColorSpace`, sRGB. A color conversion is done if necessary. The pixel value is specified by an array of data elements of type transferType passed in as an object reference. The returned value will be a non pre-multiplied value. For example, if the alpha is premultiplied, this method divides it out before returning the value. If the alpha value is 0, the green value is 0. If `inData` is not a primitive array of type transferType, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `inData` is not large enough to hold a pixel value for this `ColorModel`. If this `transferType` is not supported, a `UnsupportedOperationException` will be thrown. Since `ColorModel` is an abstract class, any instance must be an instance of a subclass. Subclasses inherit the implementation of this method and if they don't override it, this method throws an exception if the subclass uses a `transferType` other than `DataBuffer.TYPE_BYTE`, `DataBuffer.TYPE_USHORT`, or `DataBuffer.TYPE_INT`.
      Parameters:
        `inData` - an array of pixel values
      Returns:
        the value of the green component of the specified pixel.
      Throws:
        `ClassCastException` - if `inData` is not a primitive array of type `transferType`
        `ArrayIndexOutOfBoundsException` - if `inData` is not large enough to hold a pixel value for this `ColorModel`
        `UnsupportedOperationException` - if this `transferType` is not supported by this `ColorModel`

    - #### getBlue

          public int getBlue​(Object inData)

      Returns the blue color component for the specified pixel, scaled from 0 to 255 in the default RGB `ColorSpace`, sRGB. A color conversion is done if necessary. The pixel value is specified by an array of data elements of type transferType passed in as an object reference. The returned value is a non pre-multiplied value. For example, if the alpha is premultiplied, this method divides it out before returning the value. If the alpha value is 0, the blue value will be 0. If `inData` is not a primitive array of type transferType, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `inData` is not large enough to hold a pixel value for this `ColorModel`. If this `transferType` is not supported, a `UnsupportedOperationException` will be thrown. Since `ColorModel` is an abstract class, any instance must be an instance of a subclass. Subclasses inherit the implementation of this method and if they don't override it, this method throws an exception if the subclass uses a `transferType` other than `DataBuffer.TYPE_BYTE`, `DataBuffer.TYPE_USHORT`, or `DataBuffer.TYPE_INT`.
      Parameters:
        `inData` - an array of pixel values
      Returns:
        the value of the blue component of the specified pixel.
      Throws:
        `ClassCastException` - if `inData` is not a primitive array of type `transferType`
        `ArrayIndexOutOfBoundsException` - if `inData` is not large enough to hold a pixel value for this `ColorModel`
        `UnsupportedOperationException` - if this `transferType` is not supported by this `ColorModel`

    - #### getAlpha

          public int getAlpha​(Object inData)

      Returns the alpha component for the specified pixel, scaled from 0 to 255. The pixel value is specified by an array of data elements of type transferType passed in as an object reference. If inData is not a primitive array of type transferType, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `inData` is not large enough to hold a pixel value for this `ColorModel`. If this `transferType` is not supported, a `UnsupportedOperationException` will be thrown. Since `ColorModel` is an abstract class, any instance must be an instance of a subclass. Subclasses inherit the implementation of this method and if they don't override it, this method throws an exception if the subclass uses a `transferType` other than `DataBuffer.TYPE_BYTE`, `DataBuffer.TYPE_USHORT`, or `DataBuffer.TYPE_INT`.
      Parameters:
        `inData` - the specified pixel
      Returns:
        the alpha component of the specified pixel, scaled from 0 to 255.
      Throws:
        `ClassCastException` - if `inData` is not a primitive array of type `transferType`
        `ArrayIndexOutOfBoundsException` - if `inData` is not large enough to hold a pixel value for this `ColorModel`
        `UnsupportedOperationException` - if this `tranferType` is not supported by this `ColorModel`

    - #### getRGB

          public int getRGB​(Object inData)

      Returns the color/alpha components for the specified pixel in the default RGB color model format. A color conversion is done if necessary. The pixel value is specified by an array of data elements of type transferType passed in as an object reference. If inData is not a primitive array of type transferType, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `inData` is not large enough to hold a pixel value for this `ColorModel`. The returned value will be in a non pre-multiplied format, i.e. if the alpha is premultiplied, this method will divide it out of the color components (if the alpha value is 0, the color values will be 0).
      Parameters:
        `inData` - the specified pixel
      Returns:
        the color and alpha components of the specified pixel.
      See Also:
        `getRGBdefault()`

    - #### getDataElements

          public 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. This array can then be passed to the `WritableRaster.setDataElements(int, int, java.lang.Object)` method of a `WritableRaster` object. If the pixel variable is `null`, a new array will be allocated. If `pixel` is not `null`, it must be a primitive array of type `transferType`; otherwise, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `pixel` is not large enough to hold a pixel value for this `ColorModel`. The pixel array is returned. If this `transferType` is not supported, a `UnsupportedOperationException` will be thrown. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `rgb` - the integer pixel representation in the default RGB color model
        `pixel` - the specified pixel
      Returns:
        an array representation of the specified pixel in this `ColorModel`.
      Throws:
        `ClassCastException` - if `pixel` is not a primitive array of type `transferType`
        `ArrayIndexOutOfBoundsException` - if `pixel` is not large enough to hold a pixel value for this `ColorModel`
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`
      See Also:
        `WritableRaster.setDataElements(int, int, java.lang.Object)`, `SampleModel.setDataElements(int, int, java.lang.Object, java.awt.image.DataBuffer)`

    - #### getComponents

          public int[] getComponents​(int pixel,
                                     int[] components,
                                     int offset)

      Returns an array of unnormalized color/alpha components given a pixel in this `ColorModel`. The pixel value is specified as an `int`. An `IllegalArgumentException` will be thrown if pixel values for this `ColorModel` are not conveniently representable as a single `int` or if color component values for this `ColorModel` are not conveniently representable in the unnormalized form. For example, this method can be used to retrieve the components for a specific pixel value in a `DirectColorModel`. If the components array is `null`, a new array will be allocated. The components array will be returned. Color/alpha components are stored in the components array starting at `offset` (even if the array is allocated by this method). An `ArrayIndexOutOfBoundsException` is thrown if the components array is not `null` and is not large enough to hold all the color and alpha components (starting at offset). Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `pixel` - the specified pixel
        `components` - the array to receive the color and alpha components of the specified pixel
        `offset` - the offset into the `components` array at which to start storing the color and alpha components
      Returns:
        an array containing the color and alpha components of the specified pixel starting at the specified offset.
      Throws:
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`

    - #### getComponents

          public int[] getComponents​(Object pixel,
                                     int[] components,
                                     int offset)

      Returns an array of unnormalized color/alpha components given a pixel in this `ColorModel`. The pixel value is specified by an array of data elements of type transferType passed in as an object reference. If `pixel` is not a primitive array of type transferType, a `ClassCastException` is thrown. An `IllegalArgumentException` will be thrown if color component values for this `ColorModel` are not conveniently representable in the unnormalized form. An `ArrayIndexOutOfBoundsException` is thrown if `pixel` is not large enough to hold a pixel value for this `ColorModel`. This method can be used to retrieve the components for a specific pixel value in any `ColorModel`. If the components array is `null`, a new array will be allocated. The components array will be returned. Color/alpha components are stored in the `components` array starting at `offset` (even if the array is allocated by this method). An `ArrayIndexOutOfBoundsException` is thrown if the components array is not `null` and is not large enough to hold all the color and alpha components (starting at `offset`). Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `pixel` - the specified pixel
        `components` - an array that receives the color and alpha components of the specified pixel
        `offset` - the index into the `components` array at which to begin storing the color and alpha components of the specified pixel
      Returns:
        an array containing the color and alpha components of the specified pixel starting at the specified offset.
      Throws:
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`

    - #### getUnnormalizedComponents

          public 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. Unnormalized components are unsigned integral values between 0 and 2n - 1, where n is the number of bits for a particular component. Normalized components are float values between a per component minimum and maximum specified by the `ColorSpace` object for this `ColorModel`. An `IllegalArgumentException` will be thrown if color component values for this `ColorModel` are not conveniently representable in the unnormalized form. If the `components` array is `null`, a new array will be allocated. The `components` array will be returned. Color/alpha components are stored in the `components` array starting at `offset` (even if the array is allocated by this method). An `ArrayIndexOutOfBoundsException` is thrown if the `components` array is not `null` and is not large enough to hold all the color and alpha components (starting at `offset`). An `IllegalArgumentException` is thrown if the `normComponents` array is not large enough to hold all the color and alpha components starting at `normOffset`.
      Parameters:
        `normComponents` - an array containing normalized components
        `normOffset` - the offset into the `normComponents` array at which to start retrieving normalized components
        `components` - an array that receives the components from `normComponents`
        `offset` - the index into `components` at which to begin storing normalized components from `normComponents`
      Returns:
        an array containing unnormalized color and alpha components.
      Throws:
        `IllegalArgumentException` - If the component values for this `ColorModel` are not conveniently representable in the unnormalized form.
        `IllegalArgumentException` - if the length of `normComponents` minus `normOffset` is less than `numComponents`
        `UnsupportedOperationException` - if the constructor of this `ColorModel` called the `super(bits)` constructor, but did not override this method. See the constructor, `ColorModel(int)`.

    - #### getNormalizedComponents

          public 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. Unnormalized components are unsigned integral values between 0 and 2n - 1, where n is the number of bits for a particular component. Normalized components are float values between a per component minimum and maximum specified by the `ColorSpace` object for this `ColorModel`. An `IllegalArgumentException` will be thrown if color component values for this `ColorModel` are not conveniently representable in the unnormalized form. If the `normComponents` array is `null`, a new array will be allocated. The `normComponents` array will be returned. Color/alpha components are stored in the `normComponents` array starting at `normOffset` (even if the array is allocated by this method). An `ArrayIndexOutOfBoundsException` is thrown if the `normComponents` array is not `null` and is not large enough to hold all the color and alpha components (starting at `normOffset`). An `IllegalArgumentException` is thrown if the `components` array is not large enough to hold all the color and alpha components starting at `offset`.

      Since `ColorModel` is an abstract class, any instance is an instance of a subclass. The default implementation of this method in this abstract class assumes that component values for this class are conveniently representable in the unnormalized form. Therefore, subclasses which may have instances which do not support the unnormalized form must override this method.

      Parameters:
        `components` - an array containing unnormalized components
        `offset` - the offset into the `components` array at which to start retrieving unnormalized components
        `normComponents` - an array that receives the normalized components
        `normOffset` - the index into `normComponents` at which to begin storing normalized components
      Returns:
        an array containing normalized color and alpha components.
      Throws:
        `IllegalArgumentException` - If the component values for this `ColorModel` are not conveniently representable in the unnormalized form.
        `UnsupportedOperationException` - if the constructor of this `ColorModel` called the `super(bits)` constructor, but did not override this method. See the constructor, `ColorModel(int)`.
        `UnsupportedOperationException` - if this method is unable to determine the number of bits per component

    - #### getDataElement

          public 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. This method will throw an `IllegalArgumentException` if component values for this `ColorModel` are not conveniently representable as a single `int` or if color component values for this `ColorModel` are not conveniently representable in the unnormalized form. An `ArrayIndexOutOfBoundsException` is thrown if the `components` array is not large enough to hold all the color and alpha components (starting at `offset`). Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `components` - an array of unnormalized color and alpha components
        `offset` - the index into `components` at which to begin retrieving the color and alpha components
      Returns:
        an `int` pixel value in this `ColorModel` corresponding to the specified components.
      Throws:
        `IllegalArgumentException` - if pixel values for this `ColorModel` are not conveniently representable as a single `int`
        `IllegalArgumentException` - if component values for this `ColorModel` are not conveniently representable in the unnormalized form
        `ArrayIndexOutOfBoundsException` - if the `components` array is not large enough to hold all of the color and alpha components starting at `offset`
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`

    - #### getDataElements

          public 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. This array can then be passed to the `setDataElements` method of a `WritableRaster` object. This method will throw an `IllegalArgumentException` if color component values for this `ColorModel` are not conveniently representable in the unnormalized form. An `ArrayIndexOutOfBoundsException` is thrown if the `components` array is not large enough to hold all the color and alpha components (starting at `offset`). If the `obj` variable is `null`, a new array will be allocated. If `obj` is not `null`, it must be a primitive array of type transferType; otherwise, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `obj` is not large enough to hold a pixel value for this `ColorModel`. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `components` - an array of unnormalized color and alpha components
        `offset` - the index into `components` at which to begin retrieving color and alpha components
        `obj` - the `Object` representing an array of color and alpha components
      Returns:
        an `Object` representing an array of color and alpha components.
      Throws:
        `ClassCastException` - if `obj` is not a primitive array of type `transferType`
        `ArrayIndexOutOfBoundsException` - if `obj` is not large enough to hold a pixel value for this `ColorModel` or the `components` array is not large enough to hold all of the color and alpha components starting at `offset`
        `IllegalArgumentException` - if component values for this `ColorModel` are not conveniently representable in the unnormalized form
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`
      See Also:
        `WritableRaster.setDataElements(int, int, java.lang.Object)`, `SampleModel.setDataElements(int, int, java.lang.Object, java.awt.image.DataBuffer)`

    - #### getDataElement

          public 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. This method will throw an `IllegalArgumentException` if pixel values for this `ColorModel` are not conveniently representable as a single `int`. An `ArrayIndexOutOfBoundsException` is thrown if the `normComponents` array is not large enough to hold all the color and alpha components (starting at `normOffset`). Since `ColorModel` is an abstract class, any instance is an instance of a subclass. The default implementation of this method in this abstract class first converts from the normalized form to the unnormalized form and then calls `getDataElement(int[], int)`. Subclasses which may have instances which do not support the unnormalized form must override this method.
      Parameters:
        `normComponents` - an array of normalized color and alpha components
        `normOffset` - the index into `normComponents` at which to begin retrieving the color and alpha components
      Returns:
        an `int` pixel value in this `ColorModel` corresponding to the specified components.
      Throws:
        `IllegalArgumentException` - if pixel values for this `ColorModel` are not conveniently representable as a single `int`
        `ArrayIndexOutOfBoundsException` - if the `normComponents` array is not large enough to hold all of the color and alpha components starting at `normOffset`
      Since:
        1.4

    - #### getDataElements

          public 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. This array can then be passed to the `setDataElements` method of a `WritableRaster` object. An `ArrayIndexOutOfBoundsException` is thrown if the `normComponents` array is not large enough to hold all the color and alpha components (starting at `normOffset`). If the `obj` variable is `null`, a new array will be allocated. If `obj` is not `null`, it must be a primitive array of type transferType; otherwise, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `obj` is not large enough to hold a pixel value for this `ColorModel`. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. The default implementation of this method in this abstract class first converts from the normalized form to the unnormalized form and then calls `getDataElement(int[], int, Object)`. Subclasses which may have instances which do not support the unnormalized form must override this method.
      Parameters:
        `normComponents` - an array of normalized color and alpha components
        `normOffset` - the index into `normComponents` at which to begin retrieving color and alpha components
        `obj` - a primitive data array to hold the returned pixel
      Returns:
        an `Object` which is a primitive data array representation of a pixel
      Throws:
        `ClassCastException` - if `obj` is not a primitive array of type `transferType`
        `ArrayIndexOutOfBoundsException` - if `obj` is not large enough to hold a pixel value for this `ColorModel` or the `normComponents` array is not large enough to hold all of the color and alpha components starting at `normOffset`
      Since:
        1.4
      See Also:
        `WritableRaster.setDataElements(int, int, java.lang.Object)`, `SampleModel.setDataElements(int, int, java.lang.Object, java.awt.image.DataBuffer)`

    - #### getNormalizedComponents

          public 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`. The pixel value is specified by an array of data elements of type transferType passed in as an object reference. If pixel is not a primitive array of type transferType, a `ClassCastException` is thrown. An `ArrayIndexOutOfBoundsException` is thrown if `pixel` is not large enough to hold a pixel value for this `ColorModel`. Normalized components are float values between a per component minimum and maximum specified by the `ColorSpace` object for this `ColorModel`. If the `normComponents` array is `null`, a new array will be allocated. The `normComponents` array will be returned. Color/alpha components are stored in the `normComponents` array starting at `normOffset` (even if the array is allocated by this method). An `ArrayIndexOutOfBoundsException` is thrown if the `normComponents` array is not `null` and is not large enough to hold all the color and alpha components (starting at `normOffset`). Since `ColorModel` is an abstract class, any instance is an instance of a subclass. The default implementation of this method in this abstract class first retrieves color and alpha components in the unnormalized form using `getComponents(Object, int[], int)` and then calls `getNormalizedComponents(int[], int, float[], int)`. Subclasses which may have instances which do not support the unnormalized form must override this method.
      Parameters:
        `pixel` - the specified pixel
        `normComponents` - an array to receive the normalized components
        `normOffset` - the offset into the `normComponents` array at which to start storing normalized components
      Returns:
        an array containing normalized color and alpha components.
      Throws:
        `ClassCastException` - if `pixel` is not a primitive array of type transferType
        `ArrayIndexOutOfBoundsException` - if `normComponents` is not large enough to hold all color and alpha components starting at `normOffset`
        `ArrayIndexOutOfBoundsException` - if `pixel` is not large enough to hold a pixel value for this `ColorModel`.
        `UnsupportedOperationException` - if the constructor of this `ColorModel` called the `super(bits)` constructor, but did not override this method. See the constructor, `ColorModel(int)`.
        `UnsupportedOperationException` - if this method is unable to determine the number of bits per component
      Since:
        1.4

    - #### equals

          public boolean equals​(Object obj)

      This method simply delegates to the default implementation in `Object` which is identical to an `==` test since this class cannot enforce the issues of a proper equality test among multiple independent subclass branches. Subclasses are encouraged to override this method and provide equality testing for their own properties in addition to equality tests for the following common base properties of `ColorModel`:
      - Support for alpha component.
      - Is alpha premultiplied.
      - Number of bits per pixel.
      - Type of transparency like Opaque, Bitmask or Translucent.
      - Number of components in a pixel.
      - `ColorSpace` type.
      - Type of the array used to represent pixel values.
      - Number of significant bits per color and alpha component.
      Overrides:
        `equals` in class `Object`
      Parameters:
        `obj` - the reference object with which to compare.
      Returns:
        `true` if this object is the same as the obj argument; `false` otherwise.
      See Also:
        `Object.hashCode()`, `HashMap`

    - #### hashCode

          public int hashCode()

      This method simply delegates to the default implementation in `Object` which returns the system ID for the class. Subclasses are encouraged to override this method and provide a hash for their own properties in addition to hashing the values of the following common base properties of `ColorModel`:
      - Support for alpha component.
      - Is alpha premultiplied.
      - Number of bits per pixel.
      - Type of transparency like Opaque, Bitmask or Translucent.
      - Number of components in a pixel.
      - `ColorSpace` type.
      - Type of the array used to represent pixel values.
      - Number of significant bits per color and alpha component.
      Overrides:
        `hashCode` in class `Object`
      Returns:
        a hash code value for this object.
      See Also:
        `Object.equals(java.lang.Object)`, `System.identityHashCode(java.lang.Object)`

    - #### getColorSpace

          public final ColorSpace getColorSpace()

      Returns the `ColorSpace` associated with this `ColorModel`.
      Returns:
        the `ColorSpace` of this `ColorModel`.

    - #### coerceData

          public 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`. It may multiply or divide the color raster data by alpha, or do nothing if the data is in the correct state. If the data needs to be coerced, this method will also return an instance of this `ColorModel` with the `isAlphaPremultiplied` flag set appropriately. This method will throw a `UnsupportedOperationException` if it is not supported by this `ColorModel`. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `raster` - the `WritableRaster` data
        `isAlphaPremultiplied` - `true` if the alpha is premultiplied; `false` otherwise
      Returns:
        a `ColorModel` object that represents the coerced data.

    - #### isCompatibleRaster

          public boolean isCompatibleRaster​(Raster raster)

      Returns `true` if `raster` is compatible with this `ColorModel` and `false` if it is not. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `raster` - the `Raster` object to test for compatibility
      Returns:
        `true` if `raster` is compatible with this `ColorModel`.
      Throws:
        `UnsupportedOperationException` - if this method has not been implemented for this `ColorModel`

    - #### createCompatibleWritableRaster

          public 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`. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `w` - the width to apply to the new `WritableRaster`
        `h` - the height to apply to the new `WritableRaster`
      Returns:
        a `WritableRaster` object with the specified width and height.
      Throws:
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`
      See Also:
        `WritableRaster`, `SampleModel`

    - #### createCompatibleSampleModel

          public SampleModel createCompatibleSampleModel​(int w,
                                                         int h)

      Creates a `SampleModel` with the specified width and height that has a data layout compatible with this `ColorModel`. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `w` - the width to apply to the new `SampleModel`
        `h` - the height to apply to the new `SampleModel`
      Returns:
        a `SampleModel` object with the specified width and height.
      Throws:
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`
      See Also:
        `SampleModel`

    - #### isCompatibleSampleModel

          public boolean isCompatibleSampleModel​(SampleModel sm)

      Checks if the `SampleModel` is compatible with this `ColorModel`. Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method since the implementation in this abstract class throws an `UnsupportedOperationException`.
      Parameters:
        `sm` - the specified `SampleModel`
      Returns:
        `true` if the specified `SampleModel` is compatible with this `ColorModel`; `false` otherwise.
      Throws:
        `UnsupportedOperationException` - if this method is not supported by this `ColorModel`
      See Also:
        `SampleModel`

    - #### finalize

          @Deprecated(since="9")
          public void finalize()

      Deprecated.
      The `finalize` method has been deprecated. Subclasses that override `finalize` in order to perform cleanup should be modified to use alternative cleanup mechanisms and to remove the overriding `finalize` method. When overriding the `finalize` method, its implementation must explicitly ensure that `super.finalize()` is invoked as described in `Object.finalize()`. See the specification for `Object.finalize()` for further information about migration options.
      Disposes of system resources associated with this `ColorModel` once this `ColorModel` is no longer referenced.
      Overrides:
        `finalize` in class `Object`
      See Also:
        `WeakReference`, `PhantomReference`

    - #### getAlphaRaster

          public 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. `ComponentColorModel` and `DirectColorModel`). This method assumes that `Raster` objects associated with such a `ColorModel` store the alpha band, if present, as the last band of image data. Returns `null` if there is no separate spatial alpha channel associated with this `ColorModel`. If this is an `IndexColorModel` which has alpha in the lookup table, this method will return `null` since there is no spatially discrete alpha channel. This method will create a new `Raster` (but will share the data array). Since `ColorModel` is an abstract class, any instance is an instance of a subclass. Subclasses must override this method to get any behavior other than returning `null` because the implementation in this abstract class returns `null`.
      Parameters:
        `raster` - the specified `Raster`
      Returns:
        a `Raster` representing the alpha channel of an image, obtained from the specified `Raster`.

    - #### toString

          public String toString()

      Returns the `String` representation of the contents of this `ColorModel` object.
      Overrides:
        `toString` in class `Object`
      Returns:
        a `String` representing the contents of this `ColorModel` object.