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Convert the given RGB color code to Hex color code
  • Last Updated : 12 Jun, 2020

Given three colors as R, G and B, convert this RGB color to 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:
256 color code is not possible as only 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 of 1 digit, add 0 to the left to make it 2 digit.
  5. Then in the final answer, add ‘#’ at the starting 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
Output:
#000000
#FFFFFF
#9183B7
#020304
-1

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