Creating random colour in Java?

Question

I want to draw random coloured points on a JPanel in a Java application. Is there any method to create random colours?

Answer 1

Use the random library:

import java.util.Random;

Then create a random generator:

Random rand = new Random();

As colours are separated into red green and blue, you can create a new random colour by creating random primary colours:

// Java 'Color' class takes 3 floats, from 0 to 1.
float r = rand.nextFloat();
float g = rand.nextFloat();
float b = rand.nextFloat();

Then to finally create the colour, pass the primary colours into the constructor:

Color randomColor = new Color(r, g, b);

---

You can also create different random effects using this method, such as creating random colours with more emphasis on certain colours ... pass in less green and blue to produce a "pinker" random colour.

// Will produce a random colour with more red in it (usually "pink-ish")
float r = rand.nextFloat();
float g = rand.nextFloat() / 2f;
float b = rand.nextFloat() / 2f;

Or to ensure that only "light" colours are generated, you can generate colours that are always > 0.5 of each colour element:

// Will produce only bright / light colours:
float r = rand.nextFloat() / 2f + 0.5;
float g = rand.nextFloat() / 2f + 0.5;
float b = rand.nextFloat() / 2f + 0.5;

There are various other colour functions that can be used with the Color class, such as making the colour brighter:

randomColor.brighter();

An overview of the Color class can be read here: http://download.oracle.com/javase/6/docs/api/java/awt/Color.html

Answer 2

A one-liner for random RGB values:

new Color((int)(Math.random() * 0x1000000))

Answer 3

If you want pleasing, pastel colors, it is best to use the HLS system.

final float hue = random.nextFloat();
// Saturation between 0.1 and 0.3
final float saturation = (random.nextInt(2000) + 1000) / 10000f;
final float luminance = 0.9f;
final Color color = Color.getHSBColor(hue, saturation, luminance);

Answer 4

Copy paste this for bright pastel rainbow colors

int R = (int)(Math.random()*256);
int G = (int)(Math.random()*256);
int B= (int)(Math.random()*256);
Color color = new Color(R, G, B); //random color, but can be bright or dull

//to get rainbow, pastel colors
Random random = new Random();
final float hue = random.nextFloat();
final float saturation = 0.9f;//1.0 for brilliant, 0.0 for dull
final float luminance = 1.0f; //1.0 for brighter, 0.0 for black
color = Color.getHSBColor(hue, saturation, luminance);

Answer 5

If you don't want it to look horrible I'd suggest defining a list of colours in an array and then using a random number generator to pick one.

If you want a truly random colour you can just generate 3 random numbers from 0 to 255 and then use the Color(int,int,int) constructor to create a new Color instance.

Random randomGenerator = new Random();
int red = randomGenerator.nextInt(256);
int green = randomGenerator.nextInt(256);
int blue = randomGenerator.nextInt(256);

Color randomColour = new Color(red,green,blue);

Answer 6

I know it's a bit late for this answer, but I've not seen anyone else put this.

Like Greg said, you want to use the Random class

Random rand = new Random();

but the difference I'm going to say is simple do this:

Color color = new Color(rand.nextInt(0xFFFFFF));

And it's as simple as that! no need to generate lots of different floats.

Answer 7

import android.graphics.Color;

import java.util.Random;

public class ColorDiagram {
    // Member variables (properties about the object)
    public String[] mColors = {
            "#39add1", // light blue
            "#3079ab", // dark blue
            "#c25975", // mauve
            "#e15258", // red
            "#f9845b", // orange
            "#838cc7", // lavender
            "#7d669e", // purple
            "#53bbb4", // aqua
            "#51b46d", // green
            "#e0ab18", // mustard
            "#637a91", // dark gray
            "#f092b0", // pink
            "#b7c0c7"  // light gray
    };

    // Method (abilities: things the object can do)
    public int getColor() {
        String color = "";

        // Randomly select a fact
        Random randomGenerator = new Random(); // Construct a new Random number generator
        int randomNumber = randomGenerator.nextInt(mColors.length);

        color = mColors[randomNumber];
        int colorAsInt = Color.parseColor(color);

        return colorAsInt;
    }
}

Answer 8

I have used this simple and clever way for creating random color in Java,

Random random = new Random();
        System.out.println(String.format("#%06x", random.nextInt(256*256*256)));

Where #%06x gives you zero-padded hex (always 6 characters long).

Answer 9

Here is a method for getting a random color:

private static Random sRandom;

public static synchronized int randomColor() {
    if (sRandom == null) {
        sRandom = new Random();
    }
    return 0xff000000 + 256 * 256 * sRandom.nextInt(256) + 256 * sRandom.nextInt(256)
            + sRandom.nextInt(256);
}

Benefits:

• Get the integer representation which can be used with java.awt.Color or android.graphics.Color
• Keep a static reference to Random.

Answer 10

You can instantiate a color with three floats (r, g, b), each between 0.0 and 1.0: http://download.oracle.com/javase/6/docs/api/java/awt/Color.html#Color(float,%20float,%20float).

Using Java's Random class you can easily instantiate a new random color as such:

Random r = new Random();
Color randomColor = new Color(r.nextFloat(), r.nextFloat(), r.nextFloat());

I can't guarantee they'll all be pretty, but they'll be random =)

Answer 11

Sure. Just generate a color using random RGB values. Like:

public Color randomColor()
{
  Random random=new Random(); // Probably really put this somewhere where it gets executed only once
  int red=random.nextInt(256);
  int green=random.nextInt(256);
  int blue=random.nextInt(256);
  return new Color(red, green, blue);
}

You might want to vary up the generation of the random numbers if you don't like the colors it comes up with. I'd guess these will tend to be fairly dark.

Answer 12

You seem to want light random colors. Not sure what you mean exactly with light. But if you want random 'rainbow colors', try this

Random r = new Random();
Color c = Color.getHSBColor(r.nextFloat(),//random hue, color
                1.0,//full saturation, 1.0 for 'colorful' colors, 0.0 for grey
                1.0 //1.0 for bright, 0.0 for black
                );

Search for HSB color model for more information.

Answer 13

package com.adil.util;

/**
* The Class RandomColor.
*
* @author Adil OUIDAD
* @URL : http://kizana.fr
*/
public class RandomColor {      
    /**
    * Gets the random color.
    *
    * @return the random color
    */
    public static String getRandomColor() {
         String[] letters = {"0","1","2","3","4","5","6","7","8","9","A","B","C","D","E","F"};
         String color = "#";
         for (int i = 0; i < 6; i++ ) {
            color += letters[(int) Math.round(Math.random() * 15)];
         }
         return color;
    }
}