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--- javacv_opencv_7-1_hs_histogram [2010/10/18 12:55]
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+++ javacv_opencv_7-1_hs_histogram [2011/04/26 13:55] (current)
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 =====javacv opencv 7.1 hs histogram=====
 This is the example 7.1 of the book [[http://oreilly.com/catalog/9780596516130|"Learning OpenCV"]] translated from C++ to [[http://code.google.com/p/javacv/|JavaCV]]. You can download the original C++ version and the other examples of the book from http://examples.oreilly.com/9780596516130/
 This example shows how to load an image, convert it to the HSV color space and create a 2D histogram of the plane H-S.
 I wrote this example in order to show a bug that existed in JavaCV. The version 20100730 still has the bug. See the last 2 posts in:
 http://groups.google.com/group/javacv/browse_thread/thread/60d9314f8f97b8a9
 You have to download the javacv source and modify the cv.java as explained in the link above. Basically you have to change the "FloatByReference[] ranges" by "Pointer ranges".
 <code java Example7_1_HS_Histogram.java>
 package examples;
 import com.sun.jna.Memory;
 import com.sun.jna.Pointer;
 import static name.audet.samuel.javacv.jna.cxcore.*;
 import static name.audet.samuel.javacv.jna.cv.*;
 import static name.audet.samuel.javacv.jna.highgui.*;
 import name.audet.samuel.javacv.*;
 import com.sun.jna.ptr.FloatByReference;
 /**
  * Adapted from the book "Learning OpenCV" by Gary Bradski and Adrian Kaehler,
  * 2008, p.203 (Example 7-1. Histogram computation and display)
  *
  * @author Octavi Estapé
  */
 public class Example7_1_HS_Histogram {
     public static void main(String[] args) {
         // Make sure to call JavaCvErrorCallback.redirectError() to prevent your
         // application from simply crashing with no warning on some error of OpenCV.
         // JavaCvErrorCallback may be subclassed for finer control of exceptions.
         new JavaCvErrorCallback().redirectError();
         IplImage src = cvLoadImage("./data/HandOutdoorColor.jpg", 1);
         if (src == null) {
             System.err.println("Could not load image file.");
         } else {
             IplImage hsv = cvCreateImage(cvGetSize(src), 8, 3);
             cvCvtColor(src, hsv, CV_BGR2HSV);
             IplImage h_plane = cvCreateImage(cvGetSize(src), 8, 1);
             IplImage s_plane = cvCreateImage(cvGetSize(src), 8, 1);
             IplImage v_plane = cvCreateImage(cvGetSize(src), 8, 1);
             cvSplit(hsv, h_plane, s_plane, v_plane, null); //cvCvtPixToPlane
             int h_bins = 30;
             int s_bins = 32;
             CvHistogram hist;
             {
                 int hist_size[] = {h_bins, s_bins};
                 float h_ranges[] = {0, 180};
                 float s_ranges[] = {0, 255};
                 float[][] ranges = {h_ranges, s_ranges};
                 Pointer rangesP = new Memory(Pointer.SIZE*ranges.length);
                 for(int i=0; i<ranges.length; i++) {
                     Pointer p = new Memory(ranges[i].length*Float.SIZE/8);
                     p.write(0, ranges[i], 0, ranges[i].length);
                     rangesP.setPointer(i*Pointer.SIZE, p);
                 }
                 hist = cvCreateHist(hist_size.length, hist_size, CV_HIST_ARRAY, rangesP, 1);
             }
             //IplImage mask = cvCreateImage(cvGetSize(src), 8, 1);
             //cvSet(mask, cvScalar(255, 255, 255, 255));
             IplImage planes[] = {h_plane, s_plane};
             IplImage.PointerByReference planesPointer = new IplImage.PointerByReference(planes);
             cvCalcHist(planesPointer, hist, 0, null);
             cvNormalizeHist(hist, 1);
             int scale = 10;
             IplImage hist_img = cvCreateImage(cvSize(h_bins*scale, s_bins*scale), 8, 3);
             cvZero(hist_img);
             FloatByReference max_value = new FloatByReference(0);
             cvGetMinMaxHistValue(hist, null, max_value, null, null);
             for(int h=0; h<h_bins; h++) {
                 for(int s=0; s<s_bins; s++) {
                     float bin_val = cvQueryHistValue_2D(hist, h, s);
                     int intensity = (int)Math.round(bin_val*255/max_value.getValue());
                     cvRectangle(hist_img,
                             cvPoint(h*scale, s*scale),
                             cvPoint((h+1)*scale-1, (s+1)*scale-1),
                             CV_RGB(intensity, intensity, intensity),
                             CV_FILLED, 8, 0
                             );
                 }
             }
             CanvasFrame frame = new CanvasFrame("Source");
             frame.showImage(src);
             CanvasFrame frame2 = new CanvasFrame("H-S Histogram");
             frame2.showImage(hist_img);
         }
     }
 }
 </code>
 ====Related pages====
   *[[3D Color Histogram]]

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javacv_opencv_7-1_hs_histogram.1287431706.txt.gz · Last modified: 2011/04/26 13:54 (external edit)