19 - RGB To Hex Conversion

Don’t say so much, just coding…

Instruction

The rgb function is incomplete. Complete it so that passing in RGB decimal values will result in a hexadecimal representation being returned. Valid decimal values for RGB are 0 - 255. Any values that fall out of that range must be rounded to the closest valid value.

Note: Your answer should always be 6 characters long, the shorthand with 3 will not work here.

The following are examples of expected output values:

rgb(255, 255, 255) # returns FFFFFF
rgb(255, 255, 300) # returns FFFFFF
rgb(0,0,0) # returns 000000
rgb(148, 0, 211) # returns 9400D3

Ruby

Init

def rgb(r, g, b)
  # complete this function
end

Sample Testing

Test.assert_equals(rgb(0, 0, 0), '000000')
Test.assert_equals(rgb(0, 0, -20), '000000')
Test.assert_equals(rgb(300,255,255), 'FFFFFF')
Test.assert_equals(rgb(173,255,47), 'ADFF2F')

Javascript

Init

function rgb(r, g, b){
  // complete this function  
}

Sample Testing

Test.assertEquals(rgb(0, 0, 0), '000000')
Test.assertEquals(rgb(0, 0, -20), '000000')
Test.assertEquals(rgb(300,255,255), 'FFFFFF')
Test.assertEquals(rgb(173,255,47), 'ADFF2F')

Thinking

想法(1): 不管傳進來的值 (r, g, b) 都先考慮當數字不在 0 ~ 255 時，需要給最大、小值
想法(2): 判斷完成後，再轉為 16 進位

圖片來源：Unsplash Jonathan Kemper

Hint & Reference

• Ruby
  • Ruby - apidock Clamp
• JavaScript
  • JS - MDN Number

Solution

Ruby

# Solution 1
def rgb(r, g, b)
  [r, g, b].map do |c|
    if c <= 0 
      "00"
    elsif c > 255
      "FF"
    else
      c.to_s(16).upcase    
    end
  end.join('')
end

# Solution 2
def rgb(r, g, b)
  "%.2X" * 3 % [r, g, b].map{ |i| [[i, 255].min, 0].max }
end

# Solution 3
def rgb(r, g, b)
  "%.2X" * 3 % [r, g, b].map{ |i| i.clamp(0, 255) }
end

Javascript

function rgb(r, g, b){
  return toHex(r) + toHex(g) + toHex(b);
}

function toHex(color) {
  if(color < 0)
    return "00";
  if(color > 255)
    return "FF";
  return ( "0" + (Number(color).toString(16)) )
                               .slice(-2)
                               .toUpperCase()
}