net.sf.basedb.util
Class ColorGenerator

java.lang.Object
  net.sf.basedb.util.ColorGenerator

public class ColorGenerator
extends Object

This class is used to generate colors for numerical values. Given a numeric range mith a start, mid and max value and one color for each of these values you can create new colors for values within the specified range.

Example:
We have the range and colors: -1 (BLUE), 0 (WHITE) , +1 (YELLOW) The value -0.5 is converted to a lighter blue and the value +0.5 is converted to a ligther yellow. Values falling outside the min or max values are assigned the endpoint colors. In this case, BLUE and YELLOW.

Version:

2.0

Author:

nicklas

Last modified

$Date: 2008-09-11 22:08:14 +0200 (Thu, 11 Sep 2008) $

Field Summary

private int[]	deltaMidMax The difference of the RGB components of the mid and max colors. [0] = red; [1] = green; [2] = blue
private int[]	deltaMinMid The difference of the RGB components of the min and mid colors. [0] = red; [1] = green; [2] = blue
static float	INVLN2 Constant holding the value of 1 / ln(2).
private boolean	log
private Color	maxColor
private float	maxValue
private Color	midColor
private float	midValue
private Color	minColor
private float	minValue
private int[]	offsetMid The RGB components of the midpoint color. [0] = red; [1] = green; [2] = blue
private int[]	offsetMin The RGB components of the min color. [0] = red; [1] = green; [2] = blue
private float	rangeMidMax The inverted difference between the max and mid values: 1 / (maxValue - midValue)
private float	rangeMinMid The inverted difference between the mid and min values: 1 / (midValue - minValue)

Constructor Summary

ColorGenerator(Color minColor, Color midColor, Color maxColor, float minValue, float midValue, float maxValue, boolean log)
Create a new color generator.

Method Summary

static Color	fromHex(String hexRGB) Convert a hexadecimal color string such as one used in HTML to a Color object.
Color	getColor(float value) Get the color for the value.
static String	toHex(Color color) Generate a hex color string from a Color object.

Methods inherited from class java.lang.Object

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

Field Detail

INVLN2

public static final float INVLN2

Constant holding the value of 1 / ln(2). It is used to calculate the two-based logarithm of values using the formula: log2(x) = ln(x) / ln(2)

minColor

private Color minColor

midColor

private Color midColor

maxColor

private Color maxColor

minValue

private float minValue

midValue

private float midValue

maxValue

private float maxValue

log

private boolean log

offsetMin

private final int[] offsetMin

The RGB components of the min color. [0] = red; [1] = green; [2] = blue

offsetMid

private final int[] offsetMid

The RGB components of the midpoint color. [0] = red; [1] = green; [2] = blue

deltaMinMid

private final int[] deltaMinMid

The difference of the RGB components of the min and mid colors. [0] = red; [1] = green; [2] = blue

deltaMidMax

private final int[] deltaMidMax

The difference of the RGB components of the mid and max colors. [0] = red; [1] = green; [2] = blue

rangeMinMid

private final float rangeMinMid

The inverted difference between the mid and min values: 1 / (midValue - minValue)

rangeMidMax

private final float rangeMidMax

The inverted difference between the max and mid values: 1 / (maxValue - midValue)

Constructor Detail

ColorGenerator

public ColorGenerator(Color minColor,
                      Color midColor,
                      Color maxColor,
                      float minValue,
                      float midValue,
                      float maxValue,
                      boolean log)

Create a new color generator.

Parameters:

minColor - The color for the minimum endpoint

midColor - The color for the midpoint

maxColor - The color for the maximum endpoint

minValue - The value for the minimum endpoint

midValue - The value for the midpoint

maxValue - The value for the maximum endpoint

log - If values should be logarithmised before beeing assigned a color or not. Note the values in this constructor are not affected by this setting.

Throws:

InvalidDataException - If not the minValue <= midValue <= maxValue

Method Detail

fromHex

public static Color fromHex(String hexRGB)

Convert a hexadecimal color string such as one used in HTML to a Color object. The hexadecimal string must have 6 characters in the range 0-9 or A-F (case ignored).

Parameters:

hexRGB - The hexadecimal color string

Returns:

A Color object

Throws:

InvalidDataException - If the string cannot be converted

toHex

public static String toHex(Color color)

Generate a hex color string from a Color object. Useful for outputting into HTML pages.

Parameters:

color - The color object

Returns:

The hexadecimal representation of the color

getColor

public Color getColor(float value)

Get the color for the value. If the log flag was true when creating the generator the value is first logarithmised. Note that negative values can't be logarithmised so null is returned in those cases.

If the value is lower than the min endpoint the min endpoint color is returned. If the value is higher than the max endpoint the max endpoint color is returned. Otherwise a new color is calculated based on the difference between the value and the given points.

Parameters:

value - The value

Returns:

A color object or null if no color could be generated