Converting Integers to Bitmap Color

[mfawad]

Please Help...!
Hi, I am trying to replace color in bmp image. I tried making unsigned char variable directly equal to some value...
like
unsigned char oldr=255, oldg=255, oldb=0
This works pretty fine.

But now I want to take that color as input from the user.
When I use cin stream, it takes 255 as three characters, so directly getting input to unsigned char is not working.
I tried to take input to integer and then typecast to char...
But that is not working. I tried to print the characters and that characters, sometimes, are fine with respect to ASCII table. and sometimes only show spaces. But don't work in bitmap.
Kindly Help me...!

unsigned int inewr, inewg, inewb, ioldr, ioldg, ioldb // Creating Integers;
cout << "Enter R - G - B of Color to Replace: ";
cin  >> ioldr >> ioldg >> ioldb; // Taking Integers of Old Color From User
cout << "Enter R - G - B of New: ";
cin >> inewr >> inewg >> inewb;  // Taking Integers of New Color From User
// Type casting to char
unsigned char newr=inewr, newg=inewg, newb=inewb, oldr=ioldr, oldg=ioldr, oldb=ioldb;
cout << newr << " " << newg << " " << newb << endl; // Printing out characters
cout << oldr << " " << oldg << " " << oldb << endl;

// Checking color and writing in file...

for (int j=0; j<height; j++) {
	for (int i=0; i<width*3; i+=3) {
			b = mainarray[i][j];
			g = mainarray[i+1][j]; 
			r = mainarray[i+2][j];
			if ( r==oldr && g==oldg && b==oldb) {
				fout.write((char*) &newb, 1);
				fout.write((char*) &newg, 1);
				fout.write((char*) &newr, 1);
			} else {
				fout.write((char*) &b, 1);
				fout.write((char*) &g, 1);
				fout.write((char*) &r, 1);
			}
		}
	}

Note: Arrays and all other things are ok in the code that I didn't show you...
Just there is problem in type casting. As I said putting oldr=255 works very fine...
Also I am not using any library. It is for 24-bit bitmap images

[shadder]

I think you are looking for this

http://www.cplusplus.com/reference/cstdlib/atoi/

[48T7M4Gy]

It strikes me that the OP is confused about color systems. Each color is made up of 24 bits i.e. 3- 8 bit bytes with each byte capable of having a value between 0-255. There is no apparent reason to store the bytes as characters. If you do then the integer value conversion from char to int for char xyz is xyz- '0' but that seems to me to be a waste of time/effort if I understand the intent correctly.

The convention for 24 bit color and setup is explained at http://www.rapidtables.com/web/color/RGB_Color.htm