The development of the algorithm for the luminance component [Paper:Novel Histogram Processing for Colour Image Enhancement]

LuminousComponent.c

#include <stdio.h>

float H(int);			// Histogram data function
int value = 0;			// color value [0-255] used in result
int result[255];		// store the ranges
int max_recursion = 8;	// 8 recursion as mentioned in paper 2^8 = 256 intervals

/**
 * Find intermediate cut C for which sum(H[start-C]) is equal to sum(H[C-end])
 * for a given range
 * 
 * start - start of range (included)
 * end - end of range (excluded)
 * alpha - user defined parameter
 * depth - recursion depth (program concluded when maximum depth is reached)
 * 
*/
void findCutAndDivide(int start, int end, float alpha, int depth){
	
	if(depth == max_recursion) {
		
		// write color value to result array 
		// when we are at lowest level of recursion

		value++;	// update global value
		
		for(int i=start; i<end; ++i){
			result[i] = value;
		}

		return;
	}

	float left_count = 0.0f;	// sum on left side from start
	float total_count = 0.0f;	// total sum of histogram values from start to end (excluded)
	int beta, C;
	
	// count total histogram sum
	for(int i=start; i<end; ++i){
		total_count += H(i);
	}

	// find a beta which divides histogram sum in two parts
	for(int i=start; i<end; ++i){
		left_count += H(i);
		if(left_count >= total_count - left_count) {
			beta = i;
			break;
		}
	}

	// Pivot point using formula given in paper
	C = (int)(((float)(0 + 255) / 2) + alpha * (beta - ((float)(0 + 255) / 2)));

	// Repeat same procudure recursively for left and right partitions
	// This orderering ensures that data is processed from left to right
	findCutAndDivide(start, C, alpha, depth + 1);
	findCutAndDivide(C, end, alpha, depth + 1);

}


int main(){

	float alpha = 0.0f;	// 0 <= α <= 1, user defined parameter
	
	// Initialize result
	for(int i=0; i<256; ++i) result[i] = 0;
	
	// Start procecure
	findCutAndDivide(0, 256, alpha, 0);

	return 0;

}