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Convert the given RGB color code to Hex color code

  • Last Updated : 19 May, 2021

Given three colors, such as R, G, and B, convert these RGB color to a hex color code. If the conversion is not possible, print -1.

Examples: 

Input: R = 0, G = 0, B = 0 
Output: #000000

Input: R = 255, G = 255, B = 256 
Output: -1 
Explanation: 
A 256 color code is not possible as only the 0-255 range is available for a color.  

Approach:



  1. First, check if each of the given colors is in the range 0-255 or not.
  2. If not, then print -1 and exit the program as no conversion is possible in this case.
  3. If they are in range, then for each color, convert the given color code into its equivalent hexadecimal number.
  4. If the hexadecimal value is 1 digit, add 0 to the left to make it 2 digits.
  5. Then, in the final answer, add ‘#’ at the start, followed by the hexadecimal values of R, G, and B respectively.

Below is the implementation of the above approach. 

C++




// C++ code to convert the given RGB
// color code to Hex color code
 
#include <iostream>
using namespace std;
 
// function to convert decimal to hexadecimal
string decToHexa(int n)
{
    // char array to store hexadecimal number
    char hexaDeciNum[2];
 
    // counter for hexadecimal number array
    int i = 0;
    while (n != 0) {
 
        // temporary variable to store remainder
        int temp = 0;
 
        // storing remainder in temp variable.
        temp = n % 16;
 
        // check if temp < 10
        if (temp < 10) {
            hexaDeciNum[i] = temp + 48;
            i++;
        }
        else {
            hexaDeciNum[i] = temp + 55;
            i++;
        }
 
        n = n / 16;
    }
 
    string hexCode = "";
    if (i == 2) {
        hexCode.push_back(hexaDeciNum[0]);
        hexCode.push_back(hexaDeciNum[1]);
    }
    else if (i == 1) {
        hexCode = "0";
        hexCode.push_back(hexaDeciNum[0]);
    }
    else if (i == 0)
        hexCode = "00";
 
    // Return the equivalent
    // hexadecimal color code
    return hexCode;
}
 
// Function to convert the
// RGB code to Hex color code
string convertRGBtoHex(int R, int G, int B)
{
    if ((R >= 0 && R <= 255)
        && (G >= 0 && G <= 255)
        && (B >= 0 && B <= 255)) {
 
        string hexCode = "#";
        hexCode += decToHexa(R);
        hexCode += decToHexa(G);
        hexCode += decToHexa(B);
 
        return hexCode;
    }
 
    // The hex color code doesn't exist
    else
        return "-1";
}
 
// Driver program to test above function
int main()
{
    int R = 0, G = 0, B = 0;
    cout << convertRGBtoHex(R, G, B) << endl;
 
    R = 255, G = 255, B = 255;
    cout << convertRGBtoHex(R, G, B) << endl;
 
    R = 25, G = 56, B = 123;
    cout << convertRGBtoHex(R, G, B) << endl;
 
    R = 2, G = 3, B = 4;
    cout << convertRGBtoHex(R, G, B) << endl;
 
    R = 255, G = 255, B = 256;
    cout << convertRGBtoHex(R, G, B) << endl;
 
    return 0;
}

Java




// Java code to convert the given RGB
// color code to Hex color code
  
 
import java.util.*;
 
class GFG{
  
// function to convert decimal to hexadecimal
static String decToHexa(int n)
{
    // char array to store hexadecimal number
    char []hexaDeciNum = new char[2];
  
    // counter for hexadecimal number array
    int i = 0;
    while (n != 0) {
  
        // temporary variable to store remainder
        int temp = 0;
  
        // storing remainder in temp variable.
        temp = n % 16;
  
        // check if temp < 10
        if (temp < 10) {
            hexaDeciNum[i] = (char) (temp + 48);
            i++;
        }
        else {
            hexaDeciNum[i] = (char) (temp + 55);
            i++;
        }
  
        n = n / 16;
    }
  
    String hexCode = "";
    if (i == 2) {
        hexCode+=hexaDeciNum[0];
        hexCode+=hexaDeciNum[1];
    }
    else if (i == 1) {
        hexCode = "0";
        hexCode+=hexaDeciNum[0];
    }
    else if (i == 0)
        hexCode = "00";
  
    // Return the equivalent
    // hexadecimal color code
    return hexCode;
}
  
// Function to convert the
// RGB code to Hex color code
static String convertRGBtoHex(int R, int G, int B)
{
    if ((R >= 0 && R <= 255)
        && (G >= 0 && G <= 255)
        && (B >= 0 && B <= 255)) {
  
        String hexCode = "#";
        hexCode += decToHexa(R);
        hexCode += decToHexa(G);
        hexCode += decToHexa(B);
  
        return hexCode;
    }
  
    // The hex color code doesn't exist
    else
        return "-1";
}
  
// Driver program to test above function
public static void main(String[] args)
{
    int R = 0, G = 0, B = 0;
    System.out.print(convertRGBtoHex(R, G, B) +"\n");
  
    R = 255; G = 255; B = 255;
    System.out.print(convertRGBtoHex(R, G, B) +"\n");
  
    R = 25; G = 56; B = 123;
    System.out.print(convertRGBtoHex(R, G, B) +"\n");
  
    R = 2; G = 3; B = 4;
    System.out.print(convertRGBtoHex(R, G, B) +"\n");
  
    R = 255; G = 255; B = 256;
    System.out.print(convertRGBtoHex(R, G, B) +"\n");
  
}
}
 
// This code is contributed by 29AjayKumar

Python3




# Python3 program to convert the given
# RGB color code to Hex color code
 
# Function to convert decimal to hexadecimal
def decToHexa(n):
 
    # char array to store hexadecimal number
    hexaDeciNum = ['0'] * 100
 
    # Counter for hexadecimal number array
    i = 0
     
    while (n != 0):
 
        # Temporary variable to store remainder
        temp = 0
 
        # Storing remainder in temp variable.
        temp = n % 16
 
        # Check if temp < 10
        if (temp < 10):
            hexaDeciNum[i] = chr(temp + 48)
            i = i + 1
 
        else:
            hexaDeciNum[i] = chr(temp + 55)
            i = i + 1
 
        n = int(n / 16)
 
    hexCode = ""
    if (i == 2):
        hexCode = hexCode + hexaDeciNum[0]
        hexCode = hexCode + hexaDeciNum[1]
 
    elif (i == 1):
        hexCode = "0"
        hexCode = hexCode + hexaDeciNum[0]
 
    elif (i == 0):
        hexCode = "00"
 
    # Return the equivalent
    # hexadecimal color code
    return hexCode
 
# Function to convert the
# RGB code to Hex color code
def convertRGBtoHex(R, G, B):
 
    if ((R >= 0 and R <= 255) and
        (G >= 0 and G <= 255) and
        (B >= 0 and B <= 255)):
 
        hexCode = "#";
        hexCode = hexCode + decToHexa(R)
        hexCode = hexCode + decToHexa(G)
        hexCode = hexCode + decToHexa(B)
        return hexCode
 
    # The hex color code doesn't exist
    else:
        return "-1"
 
# Driver Code
R = 0
G = 0
B = 0
print (convertRGBtoHex(R, G, B))
 
R = 255
G = 255
B = 255
print (convertRGBtoHex(R, G, B))
 
R = 25
G = 56
B = 123
print (convertRGBtoHex(R, G, B))
 
R = 2
G = 3
B = 4
print (convertRGBtoHex(R, G, B))
 
R = 255
G = 255
B = 256
print (convertRGBtoHex(R, G, B))
 
# This code is contributed by Pratik Basu

C#




// C# code to convert the given RGB
// color code to Hex color code
using System;
 
class GFG{
 
// Function to convert decimal
// to hexadecimal
static string decToHexa(int n)
{
     
    // char array to store
    // hexadecimal number
    char []hexaDeciNum = new char[2];
 
    // Counter for hexadecimal
    // number array
    int i = 0;
    while (n != 0)
    {
 
        // Temporary variable to
        // store remainder
        int temp = 0;
 
        // Storing remainder in
        // temp variable.
        temp = n % 16;
 
        // Check if temp < 10
        if (temp < 10)
        {
            hexaDeciNum[i] = (char) (temp + 48);
            i++;
        }
        else
        {
            hexaDeciNum[i] = (char) (temp + 55);
            i++;
        }
        n = n / 16;
    }
    string hexCode = "";
     
    if (i == 2)
    {
        hexCode += hexaDeciNum[0];
        hexCode += hexaDeciNum[1];
    }
    else if (i == 1)
    {
        hexCode = "0";
        hexCode += hexaDeciNum[0];
    }
    else if (i == 0)
        hexCode = "00";
 
    // Return the equivalent
    // hexadecimal color code
    return hexCode;
}
 
// Function to convert the
// RGB code to Hex color code
static string convertRGBtoHex(int R, int G,
                                     int B)
{
    if ((R >= 0 && R <= 255) &&
        (G >= 0 && G <= 255) &&
        (B >= 0 && B <= 255))
    {
        string hexCode = "#";
        hexCode += decToHexa(R);
        hexCode += decToHexa(G);
        hexCode += decToHexa(B);
 
        return hexCode;
    }
 
    // The hex color code doesn't exist
    else
        return "-1";
}
 
// Driver code
public static void Main(string[] args)
{
    int R = 0, G = 0, B = 0;
    Console.Write(convertRGBtoHex(R, G, B) + "\n");
 
    R = 255; G = 255; B = 255;
    Console.Write(convertRGBtoHex(R, G, B) + "\n");
 
    R = 25; G = 56; B = 123;
    Console.Write(convertRGBtoHex(R, G, B) + "\n");
 
    R = 2; G = 3; B = 4;
    Console.Write(convertRGBtoHex(R, G, B) + "\n");
 
    R = 255; G = 255; B = 256;
    Console.Write(convertRGBtoHex(R, G, B) + "\n");
}
}
 
// This code is contributed by rutvik_56

Javascript




<script>
 
// Javascript code to convert the given RGB
// color code to Hex color code
 
// function to convert decimal to hexadecimal
function decToHexa(n)
{
    // char array to store hexadecimal number
    let hexaDeciNum = Array.from({length: 2}, (_, i) => 0);
    
    // counter for hexadecimal number array
    let i = 0;
    while (n != 0) {
    
        // temporary variable to store remainder
        let temp = 0;
    
        // storing remainder in temp variable.
        temp = n % 16;
    
        // check if temp < 10
        if (temp < 10) {
            hexaDeciNum[i] = String.fromCharCode(temp + 48);
            i++;
        }
        else {
            hexaDeciNum[i] =  String.fromCharCode(temp + 55);
            i++;
        }
    
        n = Math.floor(n / 16);
    }
    
    let hexCode = "";
    if (i == 2) {
        hexCode+=hexaDeciNum[0];
        hexCode+=hexaDeciNum[1];
    }
    else if (i == 1) {
        hexCode = "0";
        hexCode+=hexaDeciNum[0];
    }
    else if (i == 0)
        hexCode = "00";
    
    // Return the equivalent
    // hexadecimal color code
    return hexCode;
}
    
// Function to convert the
// RGB code to Hex color code
function convertRGBtoHex(R, G, B)
{
    if ((R >= 0 && R <= 255)
        && (G >= 0 && G <= 255)
        && (B >= 0 && B <= 255)) {
    
        let hexCode = "#";
        hexCode += decToHexa(R);
        hexCode += decToHexa(G);
        hexCode += decToHexa(B);
    
        return hexCode;
    }
    
    // The hex color code doesn't exist
    else
        return "-1";
}
 
 
// Driver Code
     
    let R = 0, G = 0, B = 0;
    document.write(convertRGBtoHex(R, G, B) +"<br/>");
    
    R = 255; G = 255; B = 255;
    document.write(convertRGBtoHex(R, G, B) +"<br/>");
    
    R = 25; G = 56; B = 123;
    document.write(convertRGBtoHex(R, G, B) +"<br/>");
    
    R = 2; G = 3; B = 4;
    document.write(convertRGBtoHex(R, G, B) +"<br/>");
    
    R = 255; G = 255; B = 256;
    document.write(convertRGBtoHex(R, G, B) +"<br/>");
                
</script>
Output: 
#000000
#FFFFFF
#9183B7
#020304
-1

 

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