Intensity Levels

Intensity_levels

#include<iostream>
#include "cv.h"
#include "highgui.h"
#include <cstring>
using namespace cv;
using namespace std;

// Look up table for intensity values.
int LuT[256];

// Initialize look up table according to number of intensity levels.
// For example if steps == 2 then every value in table is either 255/2 or 255.
// similarly for steps == 4 values are 255/4 , 2* 255/4, 3* 255/4 and 255.
void lookUpTable(int steps)
{
	steps = 255/steps;

	for(int i= 0 ; i< 256; i++)
	{
		LuT[i] = (i/steps)*steps;
	}
}

void intensityLevels(Mat image, int step)
{
	// initialize LuT
	lookUpTable(step);
	int channels = image.channels();

	if(channels == 1)
	{
		for(typeof(image.begin<uchar>()) it = image.begin<uchar>(); it!=image.end<uchar>(); it++ )
		{
			// Map current intensity to new level.
			*it = LuT[*it];
		}
	}
	else if(channels == 3)
	{
		for(typeof(image.begin<Vec3b>())it = image.begin<Vec3b>(); it!= image.end<Vec3b>(); it++ )
		{
			// For every channel map intensity to new level.
			(*it)[0] = LuT[(*it)[0]];
			(*it)[1] = LuT[(*it)[1]];
			(*it)[2] = LuT[(*it)[2]];
		}
	}
}

int main()
{
	// path of image.
	string path = "res/download.jpg";

	// read color image
	Mat image = imread(path,CV_LOAD_IMAGE_GRAYSCALE);

	if(!image.data)
	{
		cout<<"fail\n";
		return -1;
	}

	// create clone of the image.

	Mat In = image.clone();

	int no_of_levels = 2;
	cout<<"Please enter no. of intensity levels"<<endl;
	cin>>no_of_levels;
	if(no_of_levels < 2 )
		no_of_levels = 2;
	//
	intensityLevels(image,no_of_levels);

	namedWindow("original",CV_WINDOW_AUTOSIZE);
	namedWindow("out",CV_WINDOW_AUTOSIZE);

	imshow("out",image);
	imshow("original",In);

	waitKey(0);

	imwrite("res/original.png",In);
	imwrite("res/out.png",image);
	return 0;
}