A VERY basic code implementation for converting from RGB colour space to YUV colour space

yuv.c

/*
 * Project Name:        	RGB to Y'UV
 * Solution Name:		RGB to Y'UV
 * Original creation date:	19/11/2011
 * Edit date:			18/01/2013
 * Programmer name:		Jamie Taylor (aka "GaProgMan")
 * File name:			YUV.c
 * 
 * Purpose of the project:
 *	I was reading through a wikipedia article on
 * 	the differences between YUV and RGB and found it
 * 	very interesting.
 * 		For those who don't know, YUV is a colour
 * 	space - a way of storing colour for digital images,
 * 	film and TV. It focuses on storing Luma
 * 	(brightness - as Y') and two chrominance (colour
 * 	- as U and V) values.
 * 		Most video and still images are stored  in
 * 	this format, as it takes into account the Human
 * 	eye's ability to perceive differences in brightness
 *	at higher definition than differences in colour. This
 * 	greatly reduces the data bandwidth required to send
 * 	and receive images and film in this format.
 * 		This short program explores the mathematical
 * 	formulae used to convert colour data from the RGB
 * 	colour space to the Y'UV colour space.
 * 		For an in-depth description Y'UV, RGB and
 * 	the formulae used, please see the following
 * 	website:
 * 			http://en.wikipedia.org/wiki/YUV
 * 
 * Formulae used:
 *	To convert from RGB to Y'UV, the following
 * 	will be used:
 * 			Y' = W[r]R + W[g]G + W[b]B
 * 			U = U[max] * (B - Y') / (1 - W[b])
 * 			V = V[max] * (R - Y') / (1 - W[r])
 * 		Where:
 * 			W[r] = 0.299
 * 			W[b] = 0.114
 * 			W[g] = 1 - W[r] - W[b] = 0.587
 * 			U[max] = 0.436
 * 			V[max] = 0.615
 * 		Note:- I have placed square brackes around
 * 	the letters in the formulae that are written in
 * 	subscript. This is to make it easier for the
 * 	reader.
 *
 *	GNU Copyright information
 *	Copyright 2011 Jamie Taylor <[email protected]>
 *
 *	This program is free software; you can redistribute
 *	it and/or modify it under the terms of the GNU General
 *	Public License as published by the Free Software
 *	Foundation; either version 2 of the License, or (at
 *	your option) any later version.
 *
 *	This program is distributed in the hope that it will
 *	be useful, but WITHOUT ANY WARRANTY; without even the
 *	implied warranty of MERCHANTABILITY or FITNESS FOR A
 *	PARTICULAR PURPOSE.  See the GNU General Public
 *	License for more details.
 *
 *	You should have received a copy of the GNU General
 *	Public License along with this program; if not, write
 *	to the Free Software Foundation, Inc., 51 Franklin
 *	Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

/* included libraries */
#include <stdio.h>

/* Constants that will be used for RGB to Y'UV */
#define WEIGHTEDRED	0.299
#define WEIGHTEDGREEN	0.587
#define WEIGHTEDBLUE	0.114
#define UMAX		0.436
#define VMAX		0.615

/* function declarations */
void convertFromRGB ();

/* global variables */
float redValue;
float greenValue;
float blueValue;
float yPrime;
float uValue;
float vValue;

int main () {

  /* read values for RGB into memory */
  printf("Please input a value for RED:");
  scanf("%f", &redValue);
  printf("Please input a value for GREEN:");
  scanf("%f", &greenValue);
  printf("Please input a value for BLUE:");
  scanf("%f", &blueValue);

  /* convert RGB to Y'UV */
  convertFromRGB();

  /*display results */
  printf("\nFor the RGB input (%.2f, %.2f, %.2f),\n",
    redValue, greenValue, blueValue);
  printf("The following Y'UV is outputted (%.2f, %.2f, %.2f)",
    yPrime, uValue, vValue);
  return 0;
}

void convertFromRGB (){
  /* 
   * implement formula:
   * Y' = W[r]R + W[g]G + W[b]B
   */
  yPrime = (WEIGHTEDRED * redValue) +
    (WEIGHTEDGREEN * greenValue) +
    (WEIGHTEDBLUE * blueValue);

  /*
   * implement formula:
   * U = U[max] * (B - Y') / (1 - W[b])
   */
  uValue = UMAX * ((blueValue - yPrime)
    / (1 - WEIGHTEDBLUE));

  /*
   * implement formula:
   * V = V[max] * (R - Y') / (1 - W[r])
   */
  vValue = VMAX * ((redValue - yPrime)
    / (1 - WEIGHTEDRED));
}