Package org.openstreetmap.josm.tools

Class ColorHelper

  • public final class ColorHelper
extends java.lang.Object
    Helper to convert from color to HTML string and back.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private ColorHelper()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static java.awt.Color alphaMultiply​(java.awt.Color color, float alphaFactor)
      Multiply the alpha value of the given color with the factor.
      static double calculateContrastRatio​(java.awt.Color first, java.awt.Color second)
      Calculate the contrast between two colors (e.g.
      private static double calculateLuminance​(java.awt.Color color)
      Calculate the relative "luminance" of a color.
      private static double calculateLuminanceStepFunction​(double color)
      This is a step function for calculateLuminance(Color)
      static java.lang.String color2html​(java.awt.Color col)
      Returns the HTML color code (6 or 8 digit).
      static java.lang.String color2html​(java.awt.Color color, boolean withAlpha)
      Returns the HTML color code (6 or 8 digit).
      static java.awt.Color complement​(java.awt.Color clr)
      Returns the complementary color of clr.
      static java.lang.Integer float2int​(java.lang.Float val)
      convert float range 0 <= x <= 1 to integer range 0..255 when dealing with colors and color alpha value
      static java.awt.Color getForegroundColor​(java.awt.Color bg)
      Determines the correct foreground color (black or white) to use for the given background, so the text will be readable.
      static java.awt.Color html2color​(java.lang.String html)
      Returns the Color for the given HTML code.
      static java.lang.Float int2float​(java.lang.Integer val)
      convert integer range 0..255 to float range 0 <= x <= 1 when dealing with colors and color alpha value

      • Methods inherited from class java.lang.Object

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

    • Method Detail

      • html2color

        public static java.awt.Color html2color​(java.lang.String html)
        Returns the Color for the given HTML code.
        Parameters:
        html - the color code
        Returns:
        the color

      • color2html

        public static java.lang.String color2html​(java.awt.Color col)
        Returns the HTML color code (6 or 8 digit).
        Parameters:
        col - The color to convert
        Returns:
        the HTML color code (6 or 8 digit)

      • color2html

        public static java.lang.String color2html​(java.awt.Color color,
                                          boolean withAlpha)
        Returns the HTML color code (6 or 8 digit).
        Parameters:
        color - The color to convert
        withAlpha - if true and alpha value < 255, return 8-digit color code, else always 6-digit
        Returns:
        the HTML color code (6 or 8 digit)
        Since:
        6655

      • getForegroundColor

        public static java.awt.Color getForegroundColor​(java.awt.Color bg)
        Determines the correct foreground color (black or white) to use for the given background, so the text will be readable.
        Parameters:
        bg - background color
        Returns:
        Color#BLACK or Color#WHITE
        Since:
        9223

      • float2int

        public static java.lang.Integer float2int​(java.lang.Float val)
        convert float range 0 <= x <= 1 to integer range 0..255 when dealing with colors and color alpha value
        Parameters:
        val - float value between 0 and 1
        Returns:
        null if val is null, the corresponding int if val is in the range 0...1. If val is outside that range, return 255

      • int2float

        public static java.lang.Float int2float​(java.lang.Integer val)
        convert integer range 0..255 to float range 0 <= x <= 1 when dealing with colors and color alpha value
        Parameters:
        val - integer value
        Returns:
        corresponding float value in range 0 <= x <= 1

      • alphaMultiply

        public static java.awt.Color alphaMultiply​(java.awt.Color color,
                                           float alphaFactor)
        Multiply the alpha value of the given color with the factor. The alpha value is clamped to 0..255
        Parameters:
        color - The color
        alphaFactor - The factor to multiply alpha with.
        Returns:
        The new color.
        Since:
        11692

      • complement

        public static java.awt.Color complement​(java.awt.Color clr)
        Returns the complementary color of clr.
        Parameters:
        clr - the color to complement
        Returns:
        the complementary color of clr

      • calculateLuminance

        private static double calculateLuminance​(java.awt.Color color)
        Calculate the relative "luminance" of a color. This is mostly useful for choosing background/foreground colours
        See Also:
        constrast ratio

      • calculateContrastRatio

        public static double calculateContrastRatio​(java.awt.Color first,
                                            java.awt.Color second)
        Calculate the contrast between two colors (e.g. Color.black and Color.white).
        Parameters:
        first - The first color to use
        second - The second color to use
        Returns:
        The contrast ratio ((L1 + 0.05)/(L2 + 0.05))
        Since:
        19236