Package 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 (to, 11 sep 2008) $

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private final int[]
    deltaMidMax
    The difference of the RGB components of the mid and max colors. [0] = red; [1] = green; [2] = blue
    private final int[]
    deltaMinMid
    The difference of the RGB components of the min and mid colors. [0] = red; [1] = green; [2] = blue
    static final 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 final int[]
    offsetMid
    The RGB components of the midpoint color. [0] = red; [1] = green; [2] = blue
    private final int[]
    offsetMin
    The RGB components of the min color. [0] = red; [1] = green; [2] = blue
    private final float
    rangeMidMax
    The inverted difference between the max and mid values: 1 / (maxValue - midValue)
    private final float
    rangeMinMid
    The inverted difference between the mid and min values: 1 / (midValue - minValue)

  • Constructor Summary

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

  • Method Summary

    Modifier and Type
    Method
    Description
    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 Details

    • 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 Details

    • 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 Details

    • 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