[Chapter 22] IndexColorModel
Author: John Zukowski
Date: Thu Jul 31 15:25:28 1997

#

| Chapter 22 java.awt.image Reference |

# IndexColorModel

## Name

IndexColorModel

##

## Description

The `IndexColorModel` class is a `ColorModel` that uses a color map lookup table (with a maximum size of 256) to convert pixel values into their alpha, red, green, and blue component parts.

## Class Definition

    public class java.awt.image.IndexColorModel
        extends java.awt.image.ColorModel {
      // Constructors
      public IndexColorModel (int bits, int size,
          byte[] colorMap, int start, boolean hasalpha);
      public IndexColorModel (int bits, int size,
          byte[] colorMap, int start, boolean hasalpha, int transparent);
      public IndexColorModel (int bits, int size,
          byte[] red, byte[] green, byte[] blue);
      public IndexColorModel (int bits, int size,
          byte[] red, byte[] green, byte[] blue, byte[] alpha);
      public IndexColorModel (int bits, int size,
          byte[] red, byte[] green, byte[] blue, int transparent);
      // Instance Methods
      public final int getAlpha (int pixel);
      public final void getAlphas (byte[] alphas);
      public final int getBlue (int pixel);
      public final void getBlues (byte[] blues);
      public final int getGreen (int pixel);
      public final void getGreens (byte[] greens);
      public final int getMapSize();
      public final int getRed (int pixel);
      public final void getReds (byte[] reds);
      public final int getRGB (int pixel);
      public final int getTransparentPixel();
    }

## Constructors

### IndexColorModel

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

Parameters

  bits

    The number of bits in a pixel.

  size

    The number of entries in the color map. Note: this is not the size of the `colorMap` parameter.

  colorMap

    Color component values in red, green, blue, alpha order; the alpha component is optional, and may not be present.

  start

    The starting position in `colorMap` array.

  hasalpha

    If `hasalpha` is `true`, alpha components are present in `colorMap` array.

Throws

  `ArrayIndexOutOfBoundsException`

    If `size` is invalid.

Description

  Constructs an `IndexColorModel` object with the given component settings. The size of `colorMap` must be at least `3*size+start`, if `hasalpha` is `false`; if `hasalpha` is `true`, `colorMap.length` must be at least `4*size+start`.

#### public IndexColorModel (int bits, int size, byte[] colorMap, int start, boolean hasalpha, int transparent)

Parameters

  bits

    The number of bits in a pixel.

  size

    The number of entries in the color map. Note: this is not the size of the `colorMap` parameter.

  colorMap

    Color component values in red, green, blue, alpha order; the alpha component is optional, and may not be present.

  start

    The starting position in `colorMap` array.

  hasalpha

    If `hasalpha` is `true`, alpha components are present in `colorMap` array.

  transparent

    Position of `colorMap` entry for transparent pixel entry.

Throws

  `ArrayIndexOutOfBoundsException`

    If `size` invalid.

Description

  Constructs an `IndexColorModel` object with the given component settings. The size of `colorMap` must be at least `3*size+start`, if `hasalpha` is `false`; if `hasalpha` is `true`, `colorMap.length` must be at least `4*size+start`. The color map has a transparent pixel; its location is given by `transparent`.

#### public IndexColorModel (int bits, int size, byte[] red, byte[] green, byte[] blue)

Parameters

  bits

    The number of bits in a pixel.

  size

    The number of entries in the color map.

  red

    Red color component values.

  green

    Green color component values.

  blue

    Blue color component values.

Throws

  `ArrayIndexOutOfBoundsException`

    If `size` invalid.

Description

  Constructs an `IndexColorModel` object with the given component settings. There is no alpha component. The length of the `red`, `green`, and `blue` arrays must be greater than `size`.

#### public IndexColorModel (int bits, int size, byte[] red, byte[] green, byte[] blue, byte[] alpha)

Parameters

  bits

    The number of bits in a pixel.

  size

    The number of entries in the color map.

  red

    Red color component values.

  green

    Green color component values.

  blue

    Blue color component values.

  alpha

    Alpha component values.

Throws

  `ArrayIndexOutOfBoundsException`

    If `size` is invalid.

  `NullPointerException`

    If `size` is positive and `alpha` array is `null`.

Description

  Constructs an `IndexColorModel` object with the given component settings. The length of the `red`, `green`, `blue`, and `alpha` arrays must be greater than `size`.

#### public IndexColorModel (int bits, int size, byte[] red, byte[] green, byte[] blue, int transparent)

Parameters

  bits

    The number of bits in a pixel.

  size

    The number of entries in the color map.

  red

    Red color component values.

  green

    Green color component values.

  blue

    Blue color component values.

  transparent

    Position of transparent pixel entry.

Throws

  `ArrayIndexOutOfBoundsException`

    If `size` is invalid.

Description

  Constructs an `IndexColorModel` object with the given component settings. The length of the `red`, `green`, `blue`, and `alpha` arrays must be greater than `size`. The color map has a transparent pixel; its location is given by `transparent`.

## Instance Methods

### getAlpha

#### public final int getAlpha (int pixel)

Parameters

  pixel

    A pixel encoded with this `ColorModel`.

Returns

  The current alpha setting of the pixel.

Overrides

  `ColorModel.getAlpha(``int``)`

### getAlphas

#### public final void getAlphas (byte[] alphas)

Parameters

  alphas

    The alpha values of the pixels in the color model.

Description

  Copies the alpha values from the color map into the array `alphas[]`.

### getBlue

#### public final int getBlue (int pixel)

Parameters

  pixel

    A pixel encoded with this `ColorModel`.

Returns

  The current blue setting of the pixel.

Overrides

  `ColorModel.getBlue(``int``)`

### getBlues

#### public final void getBlues (byte[] blues)

Parameters

  blues

    The blue values of the pixels in the color model.

Description

  Copies the blue values from the color map into the array `blues[]`.

### getGreen

#### public final int getGreen (int pixel)

Parameters

  pixel

    A pixel encoded with this `ColorModel`.

Returns

  The current green setting of the pixel.

Overrides

  `ColorModel.getGreen(``int``)`

### getGreens

#### public final void getGreens (byte[] greens)

Parameters

  greens

    The green values of the pixels in the color model.

Description

  Copies the green values from the color map into the array `greens[]`.

### getMapSize

#### public final int getMapSize()

Returns

  The current size of the color map table.

### getRed

#### public final int getRed (int pixel)

Parameters

  pixel

    A pixel encoded with this `ColorModel`.

Returns

  The current red setting of the pixel.

Overrides

  `ColorModel.getRed(``int``)`

### getReds

#### public final void getReds (byte[] reds)

Parameters

  reds

    The red values of the pixels in the color model.

Description

  Copies the red values from the color map into the array `reds[]`.

### getRGB

#### public final int getRGB (int pixel)

Parameters

  pixel

    A pixel encoded with this `ColorModel`.

Returns

  The current combined red, green, and blue settings of the pixel.

Overrides

  `ColorModel.getRGB(``int``)`

Description

  Gets the color of `pixel` in the default RGB color model.

### getTransparentPixel

#### public final int getTransparentPixel()

Returns

  The array index for the transparent pixel in the color model.

## See Also

`ColorModel`

ImageProducer |  | MemoryImageSource