GaProgMan · February 3, 2013 09:53 · Feb 3, 2013
diff --git a/yuv.c b/yuv.c
@@ -0,0 +1,134 @@
+/*
+ * 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 <jamie@taylorj.org.uk>
+ *
+ *	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));
+}