1:/**
   2: * Isaias Gonzalez <siderevs@gmail.com>
   3: * 1D Histogram with OpenCV
   4: */
   5:
   6:#include <cv.h>
   7:#include <cvaux.h>
   8:#include <highgui.h>
   9:#include <stdio.h>
  10:
  11:IplImage* image= 0;
  12:IplImage* imgHistogram = 0;
  13:IplImage* gray= 0;
  14:
  15:CvHistogram* hist;
  16:
  17:int main( int argc, char** argv ){
  18:
  19:    if( argc != 2 || !(image = cvLoadImage(argv[1])) )
  20:        return -1;
  21:
  22:    //size of the histogram -1D histogram
  23:    int bins = 256;
  24:    int hsize[] = {bins};
  25:
  26:    //max and min value of the histogram
  27:    float max_value = 0, min_value = 0;
  28:
  29:    //value and normalized value
  30:    float value;
  31:    int normalized;
  32:
  33:    //ranges - grayscale 0 to 256
  34:    float xranges[] = { 0, 256 };
  35:    float* ranges[] = { xranges };
  36:
  37:    //create an 8 bit single channel image to hold a
  38:    //grayscale version of the original picture
  39:    gray = cvCreateImage( cvGetSize(image), 8, 1 );
  40:    cvCvtColor( image, gray, CV_BGR2GRAY );
  41:
  42:    //Create 3 windows to show the results
  43:    cvNamedWindow("original",1);
  44:    cvNamedWindow("gray",1);
  45:    cvNamedWindow("histogram",1);
  46:
  47:    //planes to obtain the histogram, in this case just one
  48:    IplImage* planes[] = { gray };
  49:
  50:    //get the histogram and some info about it
  51:    hist = cvCreateHist( 1, hsize, CV_HIST_ARRAY, ranges,1);
  52:    cvCalcHist( planes, hist, 0, NULL);
  53:    cvGetMinMaxHistValue( hist, &min_value, &max_value);
  54:    printf("min: %f, max: %f\n", min_value, max_value);
  55:
  56:    //create an 8 bits single channel image to hold the histogram
  57:    //paint it white
  58:    imgHistogram = cvCreateImage(cvSize(bins, 50),8,1);
  59:    cvRectangle(imgHistogram, cvPoint(0,0), cvPoint(256,50), CV_RGB(255,255,255),-1);
  60:
  61:    //draw the histogram :P
  62:    for(int i=0; i < bins; i++){
  63:            value = cvQueryHistValue_1D( hist, i);
  64:            normalized = cvRound(value*50/max_value);
  65:            cvLine(imgHistogram,cvPoint(i,50), cvPoint(i,50-normalized), CV_RGB(0,0,0));
  66:    }
  67:
  68:    //show the image results
  69:    cvShowImage( "original", image );
  70:    cvShowImage( "gray", gray );
  71:    cvShowImage( "histogram", imgHistogram );
  72:
  73:    cvWaitKey();
  74:
  75:    return 0;
  76:}