I'm using Java bindings for detecting simple shapes on Android. Here's my code following the [OpenCV](http://opencv-code.com/tutorials/detecting-simple-shapes-in-an-image/) tutorial. However, I get a null pointer exception when adding the approximate curve matrix (approx) to detected rectangles list (rectangles). What am I doing wrong?
public boolean detectRectangle(){
boolean detected=false;
Imgproc.findContours(touchedRegionBin.clone(), mContours= new ArrayList(), hierarchy, Imgproc.RETR_LIST, Imgproc.CHAIN_APPROX_SIMPLE);
// private List approx = new ArrayList ();
// private MatOfPoint2f contours2f= new MatOfPoint2f();
// private MatOfPoint2f approx2f = new MatOfPoint2f();
// private List mContours = new ArrayList();
for (int i = 0; i < mContours.size(); i++)
{
mContours.get(i).convertTo(contours2f, CvType.CV_32FC2);
// Approximate contour with accuracy proportional
// to the contour perimeter
Imgproc.approxPolyDP(contours2f, approx2f, Imgproc.arcLength(contours2f, true)*0.02, true);
Converters.Mat_to_vector_Point(approx2f, approx);
// number of vertices
if (approx.size() == 4
// && Math.abs(Imgproc.contourArea(contours2f)) > 1000
// && Imgproc.isContourConvex((MatOfPoint)approx)
)
{
double maxCosine = 0;
// Get the degree (in cosines) of all corners
for( int j = 2; j < 5; j++ )
{
double cosine = Math.abs(angle( (approx.get(j%4)), approx.get(j-2), approx.get(j-1)));
maxCosine = Math.max(maxCosine, cosine);
}
if( maxCosine <= 0.3 ){
rectangles.add((MatOfPoint) approx);
boundingR = Imgproc.boundingRect(mContours.get(i));
detected= true;
}
}
}//end of for
return detected;
}
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