Posted on May 4, 2020

Daily Challenge #236 - RGB to Hex Conversion

This 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.

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

Tests:
rgb(-20,275,125)
rgb(255,255,255)

This challenge comes from jhoffner on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

Want to propose a challenge idea for a future post? Email yo+challenge@dev.to with your suggestions!

Top comments (13)

Vidit Sarkar • May 5 '20

Here is a short Python solution,

def rgb(r, g, b): return ('{:02x}'*3).format(*map(lambda x : max(0, min(255, x)), (r, g, b))).upper()

Output,

print(rgb(255, 255, 300)) # output -> FFFFFF print(rgb(0,0,0)) # output -> 000000 print(rgb(148, 0, 211)) # output -> 9400D3 print(rgb(-20,275,125)) # output -> 00FF7D print(rgb(255, 255, 255)) # output -> FFFFFF

Andrew (he/him) • May 4 '20 • Edited

Scala, providing the shortest and most elegant solution so far 😎

def rgb(r: Int, g: Int, b: Int) = { def h(x: Int) = f"${x max 0 min 255}%02X" h(r) + h(g) + h(b) }

Tests

scala> rgb(255, 255, 255) res24: String = FFFFFF scala> rgb(255, 255, 300) res25: String = FFFFFF scala> rgb(0, 0, 0) res26: String = 000000 scala> rgb(148, 0, 211) res27: String = 9400D3 scala> rgb(-20, 275, 125) res28: String = 00FF7D scala> rgb(255, 255, 255) res29: String = FFFFFF

Andrew (he/him) • May 4 '20

A similar solution in R

rgb <- function(r, g, b) { h <- function(x) toupper(format(as.hexmode(min(255, max(0, x))), width=2)) paste0(h(r), h(g), h(b)) }

Tests

> rgb(255, 255, 255) [1] "FFFFFF" > rgb(255, 255, 300) [1] "FFFFFF" > rgb(0, 0, 0) [1] "000000" > rgb(148, 0, 211) [1] "9400D3" > rgb(-20, 275, 125) [1] "00FF7D" > rgb(255, 255, 255) [1] "FFFFFF"

Ken Bellows • May 4 '20

JavaScript:

function rgb(r, g, b) { return [r,g,b].map(n => Math.max(0, Math.min(255, n)) .toString(16) .padStart(2, '0') .toUpperCase() ).join('') }

Peter • Jun 3 '20 • Edited

In rust:

// Convert number to hex string. pub fn to_hex (value: i32) -> String { let value = if value > 255 { 255 } else if value < 0 { 0 } else { value }; format!("{:02X}", value) } // Join all hex strings together from rgb input. pub fn rgb (r: i32, g: i32, b: i32) -> String { format!("{}{}{}", to_hex(r), to_hex(g), to_hex(b)) } #[cfg(test)] mod tests { use super::*; #[test] fn it_should_be_black() { assert_eq!(rgb(255, 255, 255), "FFFFFF".to_string()); } #[test] fn it_should_be_black_too() { assert_eq!(rgb(255, 255, 300), "FFFFFF".to_string()); } #[test] fn it_should_be_white() { assert_eq!(rgb(0, 0, 0), "000000".to_string()); } #[test] fn it_should_be_other() { assert_eq!(rgb(148, 0, 211), "9400D3".to_string()); } }

Rust Playground
GitHub Gist

Pavitra Golchha • May 4 '20 • Edited

BeanShell

int clip(int n) { return Math.max(0, Math.min(n, 255)); } String rgb(int r, int g, int b) { r = clip(r); g = clip(g); b = clip(b); return String.format("%02x%02x%02x", new Object[] { r, g, b}).toUpperCase(); } show(); rgb(255, 255, 255); // returns FFFFFF rgb(255, 255, 300); // returns FFFFFF rgb(0,0,0); // returns 000000 rgb(148, 0, 211); // returns 9400D3 rgb(-20,275,125); // returns 00FF7D

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Valentin • May 5 '20

Here's my solution, with C

int limit_value(int value) { if(value <= 0) { return 0; } if(value >= 255) { return 255; } return value; } char *rgb(int r, int g, int b) { r = limit_value(r); g = limit_value(g); b = limit_value(b); char *result = calloc(7, sizeof(char)); sprintf(result, "%02X%02X%02X", r, g, b); return result; }

K.V.Harish • May 16 '20 • Edited

In javascript

const toHex = (c) => { const toHex = (c) => { const hex = Math.max(0, Math.min(255, c)).toString(16); return hex.length == 1 ? `0${hex}` : hex; }; const rgb = (r, g, b) => { return `#${toHex(r)}${toHex(g)}${toHex(b)}`; }; rgb(255, 255, 255) // #ffffff rgb(255, 255, 300) // #ffffff rgb(0,0,0) // #000000 rgb(148, 0, 211) // #9400d3 rgb(-20,275,125) // #00ff7d rgb(255,255,255) // #ffffff

Craig McIlwrath • May 4 '20

Haskell solution:

import Numeric (showIntAtBase) import Data.Char (intToDigit) clamp :: (Ord a) => a -> a -> a -> a clamp mi ma x = minimum [maximum [x, mi], ma] padStart :: Int -> a -> [a] -> [a] padStart l x = until ((>=l) . length) (x:) rgb2num :: (Int, Int, Int) -> Int rgb2num (r, g, b) = clampColor r * 65536 + clampColor g * 256 + clampColor b where clampColor = clamp 0 255 rgb2hex :: (Int, Int, Int) -> String rgb2hex n = padStart 6 '0' $ showIntAtBase 16 intToDigit (rgb2num n) ""

Rohit Prasad • May 4 '20

Python

r = int(input("R: ")) g = int(input("G: ")) b = int(input("B: ")) def rgb(var): if var < 0: var = 0 if var > 255: var = 255 return hex(var).split('x')[-1].zfill(2) print('#',rgb(r), rgb(g), rgb(b), sep='')

Pavitra Golchha • May 4 '20 • Edited

You need to create a rgb function which takes three arguments. Also, this challenge didn't specify to put # at the start.

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