Map colors into names and vice versa. : Color « 2D Graphics « Java Tutorial






/**
 * 
 * LibSparkline : a free Java sparkline chart library
 * 
 *
 * Project Info:  http://reporting.pentaho.org/libsparkline/
 *
 * (C) Copyright 2008, by Larry Ogrodnek, Pentaho Corporation and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it under the terms
 * of the Apache License 2.0.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * You should have received a copy of the Apache License 2.0 along with this library;
 * if not, a online version is available at http://www.apache.org/licenses/
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
 * in the United States and other countries.]
 *
 * ------------
 * ColorUtilitiy.java
 * ------------
 */

import java.awt.Color;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.HashMap;

/**
 * A helper class to map colors into names and vice versa.
 * 
 * @author Thomas Morgner
 */
public final class ColorUtilitiy {
  private static final HashMap knownColorNamesByColor;

  private static final HashMap knownColorsByName;

  static {
    knownColorNamesByColor = new HashMap();
    knownColorsByName = new HashMap();
    try {
      final Field[] fields = Color.class.getFields();
      for (int i = 0; i < fields.length; i++) {
        final Field f = fields[i];
        if (Modifier.isPublic(f.getModifiers()) && Modifier.isFinal(f.getModifiers())
            && Modifier.isStatic(f.getModifiers())) {
          final String name = f.getName();
          final Object oColor = f.get(null);
          if (oColor instanceof Color) {
            knownColorNamesByColor.put(oColor, name.toLowerCase());
            knownColorsByName.put(name.toLowerCase(), oColor);
          }
        }
      }
    } catch (Exception e) {
      // ignore ..
    }
  }

  /**
   * Utility class constructor prevents object creation.
   */
  private ColorUtilitiy() {
  }

  /**
   * Parse a String into a Color. <p/> This method will accept either a color
   * name (a field name from {@link Color}, case insensitive e.g. "red"), or a
   * HTML hex color string (e.g. "#ff0000" for Color.RED).
   * 
   * @param value
   *          String to parse for color name or color number.
   * @return Color for s.
   */
  private static Color parseColor(final String value) {
    if (value == null) {
      return null;
    }

    final Object o = knownColorsByName.get(value.toLowerCase());
    if (o != null) {
      return (Color) o;
    }

    try {
      // get color by hex or octal value
      return Color.decode(value.trim());
    } catch (NumberFormatException nfe) {
      return null;
    }
  }

  /**
   * Parse a String into a Color, and returns the given default value if the
   * color is not parsable. <p/> This method will accept either a color name (a
   * field name from {@link Color}, case insensitive e.g. "red"), or a HTML hex
   * color string (e.g. "#ff0000" for Color.RED).
   * 
   * @param colorText
   *          String to parse for color name or color number.
   * @param defValue
   *          the default value that should be returned if the string is not
   *          parseable or null.
   * @return Color for the text.
   */
  public static Color convertColor(final String colorText, final Color defValue) {
    if (colorText == null || colorText.isEmpty()) {
      return defValue;
    }

    final Color retval = parseColor(colorText);
    if (retval == null) {
      return defValue;
    }
    return retval;
  }
}








16.10.Color
16.10.1.java.awt.Color
16.10.2.Drawing with Color
16.10.3.To compare two Color objects you can use the equals() method
16.10.4.Color class is used to work with colors in Java 2D
16.10.5.Using the getRGB() method for comparing colors
16.10.6.Convert RGB to HSB
16.10.7.Convert HSB to RGB value
16.10.8.Construct Color objectConstruct Color object
16.10.9.Constructs several colors and draws various objects using these colors:Constructs several colors and draws various objects using these colors:
16.10.10.Java Predefined Colors
16.10.11.Using color with and Bit andUsing color with and Bit and
16.10.12.Color Factory
16.10.13.Convert an integer to an HTML RGB value
16.10.14.Converts a given string into a color.
16.10.15.HTML color and Java Color
16.10.16.Converts the String representation of a color to an actual Color object.
16.10.17.Get HTML Color String from Java Color object
16.10.18.Derives a color by adding the specified offsets to the base color's hue, saturation, and brightness values
16.10.19.Set XOR mode to color blue
16.10.20.Map colors into names and vice versa.