Converting RGB to HEX in Ruby

gistfile1.rb

# Beginning Rubyists: simply run >> ruby hex-convertions.rb to see examples
# or use irb to build the code on the fly

# you can convert HEX to DEC using the method .to_i(base),
# which converts a string to a decimal number from the specified base number

puts "00".to_i(16)

puts "FF".to_i(16)

# to get from DEC to HEX, simply use the method .to_s

puts 255.to_s(16)

puts 0.to_s(16)

# easy! Now let's split a standard CSS color into it Red Green and Blue components

white = "FFFFFF"
components =  white.scan(/.{2}/)
puts components

# great, now try converting each component into DEC
components.each {|component| puts component.to_i(16)}

# given an RGB color, convert to HEX

@red_as_hex = ""
red = [255,0,0]  # I'm cutting corners here; we also need to convert the CSS string rgb(255,0,0) to the array used on the left. It's easy.
red.each {|component| @red_as_hex << component.to_s(16) }
puts @red_as_hex

# notice a slight problem in the output... we got ff00 for the HEX "red".
# We need some way to print ff0000 to get the proper CSS value
# try a simple loop for now...

@blue_as_hex = ""
blue = [0,0,255]

blue.each do |component|
  hex = component.to_s(16)
  if component < 10
    @blue_as_hex << "0#{hex}"
  else
    @blue_as_hex << hex
  end
end

puts @blue_as_hex

# Now we've got all the tricks we need to shuffle between RGB and HEX.
# Next, we can start doing additive color theory! 

Line 42 should be: if component < 16, otherwise if left as is, it will result in colors like [100,100,12] being #6464c instead of #64640c.

On Line 20, the regex could be white.scan(/[0-9A-Fa-f]{2}/), so it will also accept "#ffffff" syntax :)

You can use String#rjust to pad, so L40-47 could be blue.each {|c| c.to_s(16).rjust(2, '0')}

Also, if you found this nice gist, you might want to check out the Chroma gem. It does color parsing and manipulation and everything. 🎉