Ruby, Generate a random hex color

Question

How can I generate a random hex color with ruby?

score 149 · Answer 1 · answered Nov 08 '09 at 23:40

149

Here's one way:

colour = "%06x" % (rand * 0xffffff)

answered Nov 08 '09 at 23:40

Paige Ruten

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Could someone explain it (especially the "%06x"? – Dorian Jan 17 '12 at 05:12
9

The [% method](http://ruby-doc.org/core-1.9.3/String.html#method-i-25) on String uses the string as a format specification for the argument. "%06x" means: format a number as hex, 6 characters (digits in this case) wide, 0 padded. – Tim Gage Mar 03 '12 at 16:37
@jeremy-ruten, I had to move the accepted answer over to airled's answer, please fogive me ;) – JP Silvashy Oct 22 '18 at 17:07

score 40 · Answer 2 · edited Apr 09 '16 at 13:20

40

SecureRandom.hex(3)
#=> "fef912"

The SecureRandom module is part of Ruby's standard library

require 'securerandom'

It's autoloaded in Rails, but if you're using Rails 3.0 or lower, you'll need to use

ActiveSupport::SecureRandom.hex(3)

edited Apr 09 '16 at 13:20

Dennis

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answered Jun 29 '12 at 16:54

c-amateur

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If you are going to use this option, you will need to prepend the hex with "#". Works great, just don't forget the hash symbol at the beginning. – Eli Duke Jan 25 '18 at 07:25

score 12 · Answer 3 · edited Jul 11 '13 at 10:41

12

You can generate each component independently:

r = rand(255).to_s(16)
g = rand(255).to_s(16)
b = rand(255).to_s(16)

r, g, b = [r, g, b].map { |s| if s.size == 1 then '0' + s else s end }

color = r + g + b      # => e.g. "09f5ab"

edited Jul 11 '13 at 10:41

n1313

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answered Nov 08 '09 at 23:32

Daniel Spiewak

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This is considerably more customizable, but Jeremy's solution is much much more concise. – Benson Mar 09 '10 at 07:43
For arbitrary byte length (replace 3 w/ number of bytes): `"".tap {|s| 3.times {s << ("%02x" % rand(255))}}` – Abe Voelker Mar 28 '12 at 19:40
but this is still a cool way to do it, thumbs up for readability. – JP Silvashy Mar 04 '14 at 06:50
You should change to `rand(256)`, since this current method will limit the lightest color to `#fefefe` (highest value `rand(255)` can output is 254). – siannopollo May 27 '18 at 19:55

airled · Accepted Answer · 2019-09-06T06:10:12.857

7

One-liner with unpack: Random.new.bytes(3).unpack("H*")[0]

Since ruby 2.6.0 you can do it even shorter: Random.bytes(3).unpack1('H*')

edited Sep 06 '19 at 06:10

answered Sep 25 '18 at 13:23

airled

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Love this: `Random.bytes(3).unpack1('H*')` – netwire Apr 29 '20 at 21:44

nilid · Answer 5 · 2019-09-27T12:00:14.540

also you can do this:

colour = '#%X%X%X' % 3.times.map{ rand(255) }

some updates:

or if you want to freeze any color:

class RandomColor
  def self.get_random
    rand(255)
  end

  def self.color_hex(options = {})
    default = { red: get_random, green: get_random, blue: get_random }
    options = default.merge(options)
    '#%X%X%X' % options.values
  end
end

then

# full random colour

RandomColor.color_hex() => #299D3D
RandomColor.color_hex() => #C0E92D

# freeze any colour

RandomColor.color_hex(red: 100) => #644BD6
RandomColor.color_hex(red: 100) => #6488D9

Ruby, Generate a random hex color

5 Answers5

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