imagingbook.pub.color.quantize

Class OctreeQuantizer

java.lang.Object

imagingbook.pub.color.quantize.ColorQuantizer

imagingbook.pub.color.quantize.OctreeQuantizer

public class OctreeQuantizer
extends ColorQuantizer

This class implements color quantization based on the octree method. It is a re-factored version of an implementation (OctTreeOpImage.java) used in Sun's JAI (Java Advanced Imaging) framework, which – in turn – is based on a C implementation (quantize.c) authored by John Cristy in 1992 as part of ImageMagick. The associated source code can be found here, the original copyright note is provided at the bottom of this source file. See also the abovementioned JAI implementation in OctTreeOpImage.java. This implementation is similar but not identical to the original octree quantization algorithm proposed by Gervautz and Purgathofer [M. Gervautz and W. Purgathofer. "A simple method for color quantization: octree quantization", in A. Glassner (editor), Graphics Gems I, pp. 287–293. Academic Press, New York (1990)]. This implementation uses a modified strategy for pruning the octree for better efficiency. "Quick quantization" means that original colors are mapped to their color index by simply finding the containing octree node. Otherwise, the closest quantized color (in terms of Euclidean distance) is searched for, which is naturally slower.

Version:

2017/01/03

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	OctreeQuantizer.Parameters

Field Summary

Fields inherited from class imagingbook.pub.color.quantize.ColorQuantizer

MAX_RGB

Constructor Summary

Constructors

Constructor and Description
OctreeQuantizer(int[] pixels)
OctreeQuantizer(int[] pixels, OctreeQuantizer.Parameters params)

Method Summary

Modifier and Type	Method and Description
protected int	findColorIndex(int p) Finds the color table index of the color that is "closest" to the supplied RGB color (minimum Euclidean distance in color space).
int[][]	getColorMap() Retrieves the color map produced by this color quantizer.
void	listNodes() Lists the octree nodes to System.out (intended for debugging only).

Methods inherited from class imagingbook.pub.color.quantize.ColorQuantizer

intToRgb, listColorMap, log2, quantize, quantize, quantize, rgbToInt, sqr

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

OctreeQuantizer

public OctreeQuantizer(int[] pixels,
                       OctreeQuantizer.Parameters params)

OctreeQuantizer

public OctreeQuantizer(int[] pixels)

Method Detail

listNodes

public void listNodes()

Lists the octree nodes to System.out (intended for debugging only).

getColorMap

public int[][] getColorMap()

Description copied from class: ColorQuantizer

Retrieves the color map produced by this color quantizer. The returned array is in the format int[idx][rgb], where rgb = 0 (red), 1 (green), 2 (blue) and 0 ≤ idx < nColors. This method must be implemented by any derived concrete class.

Specified by:

getColorMap in class ColorQuantizer

Returns:

The table of quantization colors.

findColorIndex

protected int findColorIndex(int p)

Description copied from class: ColorQuantizer

Finds the color table index of the color that is "closest" to the supplied RGB color (minimum Euclidean distance in color space). This method may be overridden by inheriting classes, for example, to use quick indexing in the octree method.

Overrides:

findColorIndex in class ColorQuantizer

Parameters:

p - Original color, encoded as an ARGB integer.

Returns:

The associated color table index.