java.awt.image

## Class PackedColorModel

- java.lang.Object
- - java.awt.image.ColorModel
  - - java.awt.image.PackedColorModel

All Implemented Interfaces:
  Transparency

Direct Known Subclasses:
  DirectColorModel

    public abstract class PackedColorModel
    extends ColorModel

The `PackedColorModel` class is an abstract `ColorModel` class that works with pixel values which represent color and alpha information as separate samples and which pack all samples for a single pixel into a single int, short, or byte quantity. This class can be used with an arbitrary `ColorSpace`. The number of color samples in the pixel values must be the same as the number of color components in the `ColorSpace`. There can be a single alpha sample. The array length is always 1 for those methods that use a primitive array pixel representation of type `transferType`. The transfer types supported are DataBuffer.TYPE_BYTE, DataBuffer.TYPE_USHORT, and DataBuffer.TYPE_INT. Color and alpha samples are stored in the single element of the array in bits indicated by bit masks. Each bit mask must be contiguous and masks must not overlap. The same masks apply to the single int pixel representation used by other methods. The correspondence of masks and color/alpha samples is as follows:

- Masks are identified by indices running from 0 through `getNumComponents` - 1.
- The first `getNumColorComponents` indices refer to color samples.
- If an alpha sample is present, it corresponds the last index.
- The order of the color indices is specified by the `ColorSpace`. Typically, this reflects the name of the color space type (for example, TYPE_RGB), index 0 corresponds to red, index 1 to green, and index 2 to blue.

The translation from pixel values to color/alpha components for display or processing purposes is a one-to-one correspondence of samples to components. A `PackedColorModel` is typically used with image data that uses masks to define packed samples. For example, a `PackedColorModel` can be used in conjunction with a `SinglePixelPackedSampleModel` to construct a `BufferedImage`. Normally the masks used by the `SampleModel` and the `ColorModel` would be the same. However, if they are different, the color interpretation of pixel data is done according to the masks of the `ColorModel`.

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.

A subclass of `PackedColorModel` is `DirectColorModel`, which is similar to an X11 TrueColor visual.

See Also:
  `DirectColorModel`, `SinglePixelPackedSampleModel`, `BufferedImage`

### Field Summary

### Fields inherited from class java.awt.image.ColorModel

`pixel_bits, transferType`

### Fields inherited from interface java.awt.Transparency

`BITMASK, OPAQUE, TRANSLUCENT`

### Constructor Summary

Constructors
Constructor and Description
`PackedColorModel(ColorSpace space, int bits, int[] colorMaskArray, int alphaMask, boolean isAlphaPremultiplied, int trans, int transferType)` Constructs a `PackedColorModel` from a color mask array, which specifies which bits in an `int` pixel representation contain each of the color samples, and an alpha mask.
`PackedColorModel(ColorSpace space, int bits, int rmask, int gmask, int bmask, int amask, boolean isAlphaPremultiplied, int trans, int transferType)` Constructs a `PackedColorModel` from the specified masks which indicate which bits in an `int` pixel representation contain the alpha, red, green and blue color samples.

### Method Summary

Methods
`SampleModel` `createCompatibleSampleModel(int w, int h)` Creates a `SampleModel` with the specified width and height that has a data layout compatible with this `ColorModel`.
`boolean` `equals(Object obj)` Tests if the specified `Object` is an instance of `PackedColorModel` and equals this `PackedColorModel`.
`WritableRaster` `getAlphaRaster(WritableRaster raster)` Returns a `WritableRaster` representing the alpha channel of an image, extracted from the input `WritableRaster`.
`int` `getMask(int index)` Returns the mask indicating which bits in a pixel contain the specified color/alpha sample.
`int[]` `getMasks()` Returns a mask array indicating which bits in a pixel contain the color and alpha samples.
`boolean` `isCompatibleSampleModel(SampleModel sm)` Checks if the specified `SampleModel` is compatible with this `ColorModel`.

### Methods inherited from class java.awt.image.ColorModel

`coerceData, createCompatibleWritableRaster, finalize, getAlpha, getAlpha, getBlue, getBlue, getColorSpace, getComponents, getComponents, getComponentSize, getComponentSize, getDataElement, getDataElement, getDataElements, getDataElements, getDataElements, getGreen, getGreen, getNormalizedComponents, getNormalizedComponents, getNumColorComponents, getNumComponents, getPixelSize, getRed, getRed, getRGB, getRGB, getRGBdefault, getTransferType, getTransparency, getUnnormalizedComponents, hasAlpha, hashCode, isAlphaPremultiplied, isCompatibleRaster, toString`

### Methods inherited from class java.lang.Object

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

### Constructor Detail

#### PackedColorModel

    public PackedColorModel(ColorSpace space,
                    int bits,
                    int[] colorMaskArray,
                    int alphaMask,
                    boolean isAlphaPremultiplied,
                    int trans,
                    int transferType)

Constructs a `PackedColorModel` from a color mask array, which specifies which bits in an `int` pixel representation contain each of the color samples, and an alpha mask. Color components are in the specified `ColorSpace`. The length of `colorMaskArray` should be the number of components in the `ColorSpace`. All of the bits in each mask must be contiguous and fit in the specified number of least significant bits of an `int` pixel representation. If the `alphaMask` is 0, there is no alpha. If there is alpha, the `boolean` `isAlphaPremultiplied` specifies how to interpret color and alpha samples in pixel values. If the `boolean` is `true`, color samples are assumed to have been multiplied by the alpha sample. The transparency, `trans`, 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.

Parameters:
  `space` - the specified `ColorSpace`
  `bits` - the number of bits in the pixel values
  `colorMaskArray` - array that specifies the masks representing the bits of the pixel values that represent the color components
  `alphaMask` - specifies the mask representing the bits of the pixel values that represent the alpha component
  `isAlphaPremultiplied` - `true` if color samples are premultiplied by the alpha sample; `false` otherwise
  `trans` - specifies the alpha value that can be represented by this color model
  `transferType` - the type of array used to represent pixel values
Throws:
  `IllegalArgumentException` - if `bits` is less than 1 or greater than 32

#### PackedColorModel

    public PackedColorModel(ColorSpace space,
                    int bits,
                    int rmask,
                    int gmask,
                    int bmask,
                    int amask,
                    boolean isAlphaPremultiplied,
                    int trans,
                    int transferType)

Constructs a `PackedColorModel` from the specified masks which indicate which bits in an `int` pixel representation contain the alpha, red, green and blue color samples. Color components are in the specified `ColorSpace`, which must be of type ColorSpace.TYPE_RGB. All of the bits in each mask must be contiguous and fit in the specified number of least significant bits of an `int` pixel representation. If `amask` is 0, there is no alpha. If there is alpha, the `boolean` `isAlphaPremultiplied` specifies how to interpret color and alpha samples in pixel values. If the `boolean` is `true`, color samples are assumed to have been multiplied by the alpha sample. The transparency, `trans`, 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.

Parameters:
  `space` - the specified `ColorSpace`
  `bits` - the number of bits in the pixel values
  `rmask` - specifies the mask representing the bits of the pixel values that represent the red color component
  `gmask` - specifies the mask representing the bits of the pixel values that represent the green color component
  `bmask` - specifies the mask representing the bits of the pixel values that represent the blue color component
  `amask` - specifies the mask representing the bits of the pixel values that represent the alpha component
  `isAlphaPremultiplied` - `true` if color samples are premultiplied by the alpha sample; `false` otherwise
  `trans` - specifies the alpha value that can be represented by this color model
  `transferType` - the type of array used to represent pixel values
Throws:
  `IllegalArgumentException` - if `space` is not a TYPE_RGB space
See Also:
  `ColorSpace`

### Method Detail

#### getMask

    public final int getMask(int index)

Returns the mask indicating which bits in a pixel contain the specified color/alpha sample. For color samples, `index` corresponds to the placement of color sample names in the color space. Thus, an `index` equal to 0 for a CMYK ColorSpace would correspond to Cyan and an `index` equal to 1 would correspond to Magenta. If there is alpha, the alpha `index` would be:

          alphaIndex = numComponents() - 1;

Parameters:
  `index` - the specified color or alpha sample
Returns:
  the mask, which indicates which bits of the `int` pixel representation contain the color or alpha sample specified by `index`.
Throws:
  `ArrayIndexOutOfBoundsException` - if `index` is greater than the number of components minus 1 in this `PackedColorModel` or if `index` is less than zero

#### getMasks

    public final int[] getMasks()

Returns a mask array indicating which bits in a pixel contain the color and alpha samples.

Returns:
  the mask array , which indicates which bits of the `int` pixel representation contain the color or alpha samples.

#### 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`.

Overrides:
  `createCompatibleSampleModel` in class `ColorModel`
Parameters:
  `w` - the width (in pixels) of the region of the image data described
  `h` - the height (in pixels) of the region of the image data described
Returns:
  the newly created `SampleModel`.
Throws:
  `IllegalArgumentException` - if `w` or `h` is not greater than 0
See Also:
  `SampleModel`

#### isCompatibleSampleModel

    public boolean isCompatibleSampleModel(SampleModel sm)

Checks if the specified `SampleModel` is compatible with this `ColorModel`. If `sm` is `null`, this method returns `false`.

Overrides:
  `isCompatibleSampleModel` in class `ColorModel`
Parameters:
  `sm` - the specified `SampleModel`, or `null`
Returns:
  `true` if the specified `SampleModel` is compatible with this `ColorModel`; `false` otherwise.
See Also:
  `SampleModel`

#### getAlphaRaster

    public WritableRaster getAlphaRaster(WritableRaster raster)

Returns a `WritableRaster` representing the alpha channel of an image, extracted from the input `WritableRaster`. This method assumes that `WritableRaster` objects associated with this `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`. This method creates a new `WritableRaster`, but shares the data array.

Overrides:
  `getAlphaRaster` in class `ColorModel`
Parameters:
  `raster` - a `WritableRaster` containing an image
Returns:
  a `WritableRaster` that represents the alpha channel of the image contained in `raster`.

#### equals

    public boolean equals(Object obj)

Tests if the specified `Object` is an instance of `PackedColorModel` and equals this `PackedColorModel`.

Overrides:
  `equals` in class `ColorModel`
Parameters:
  `obj` - the `Object` to test for equality
Returns:
  `true` if the specified `Object` is an instance of `PackedColorModel` and equals this `PackedColorModel`; `false` otherwise.
See Also:
  `Object.hashCode()`, `Hashtable`

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