/**
 * Isaias Gonzalez <siderevs@gmail.com>
 * 1D Histogram with OpenCV
 */

#include <cv.h>
#include <cvaux.h>
#include <highgui.h>
#include <stdio.h>

IplImage* image= 0;
IplImage* imgHistogram = 0;
IplImage* gray= 0;

CvHistogram* hist;

int main( int argc, char** argv ){

    if( argc != 2 || !(image = cvLoadImage(argv[1])) )
        return -1;

    //size of the histogram -1D histogram
    int bins = 256;
    int hsize[] = {bins};

    //max and min value of the histogram
    float max_value = 0, min_value = 0;

    //value and normalized value
    float value;
    int normalized;

    //ranges - grayscale 0 to 256
    float xranges[] = { 0, 256 };
    float* ranges[] = { xranges };

    //create an 8 bit single channel image to hold a
    //grayscale version of the original picture
    gray = cvCreateImage( cvGetSize(image), 8, 1 );
    cvCvtColor( image, gray, CV_BGR2GRAY );

    //Create 3 windows to show the results
    cvNamedWindow("original",1);
    cvNamedWindow("gray",1);
    cvNamedWindow("histogram",1);

    //planes to obtain the histogram, in this case just one
    IplImage* planes[] = { gray };

    //get the histogram and some info about it
    hist = cvCreateHist( 1, hsize, CV_HIST_ARRAY, ranges,1);
    cvCalcHist( planes, hist, 0, NULL);
    cvGetMinMaxHistValue( hist, &min_value, &max_value);
    printf("min: %f, max: %f\n", min_value, max_value);

    //create an 8 bits single channel image to hold the histogram
    //paint it white
    imgHistogram = cvCreateImage(cvSize(bins, 50),8,1);
    cvRectangle(imgHistogram, cvPoint(0,0), cvPoint(256,50), CV_RGB(255,255,255),-1);

    //draw the histogram :P
    for(int i=0; i < bins; i++){
            value = cvQueryHistValue_1D( hist, i);
            normalized = cvRound(value*50/max_value);
            cvLine(imgHistogram,cvPoint(i,50), cvPoint(i,50-normalized), CV_RGB(0,0,0));
    }

    //show the image results
    cvShowImage( "original", image );
    cvShowImage( "gray", gray );
    cvShowImage( "histogram", imgHistogram );

    cvWaitKey();

    return 0;
}