如何在java中找到最大的轮廓opencv

Question

我已经使用查找轮廓和boundingrect并将其显示在我的项目中。那么我想找到最大的轮廓并显示它。这可能吗？我是OpenCV java lang的新手。

继承人到目前为止我的代码：

@Override 
public void onCameraViewStarted(int width, int height) { 
    mRgba = new Mat(height, width, CvType.CV_8UC4); 
    mHsv = new Mat(height,width,CvType.CV_8UC3); 
    hierarchy = new Mat(); 
    mHsvMask = new Mat(); 
    mDilated = new Mat(); 
    mEroded = new Mat(); 
} 

@Override 
public void onCameraViewStopped() { 
    mRgba.release(); 
    mHsv.release(); 
    mHsvMask.release(); 
    mDilated.release(); 
    hierarchy.release(); 

} 

@Override 
public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) { 

    mRgba =inputFrame.rgba(); 
    contours = new ArrayList<MatOfPoint>(); 
    hierarchy =new Mat(); 
    mHsv = new Mat(); 
    mHsvMask =new Mat(); 

    Imgproc.cvtColor(mRgba, mHsv, Imgproc.COLOR_RGB2HSV); 

    Scalar lowerThreshold = new Scalar (0, 0, 0); // Blue color – lower hsv values 
    Scalar upperThreshold = new Scalar (179, 255, 10); // Blue color – higher hsv values 
    Core.inRange (mHsv, lowerThreshold , upperThreshold, mHsvMask); 

    //just some filter 
    //Imgproc.dilate (mHsvMask, mDilated, new Mat()); 
    //Imgproc.erode(mDilated,mEroded,new Mat()); 


    Imgproc.findContours(mHsvMask, contours, hierarchy, Imgproc.RETR_TREE, Imgproc.CHAIN_APPROX_SIMPLE); 

    for (int contourIdx=0; contourIdx < contours.size(); contourIdx++) 
    { 
     //Minimun size allowed for consideration 
     MatOfPoint2f approxCurve = new MatOfPoint2f(); 
     MatOfPoint2f contour2f = new MatOfPoint2f(contours.get(contourIdx).toArray()); 

     //Processing on mMOP2f1 which is in type MatOfPoint2f 
     double approxDistance = Imgproc.arcLength(contour2f,true)*0.02; 
     Imgproc.approxPolyDP(contour2f,approxCurve,approxDistance,true); 

     //convert to MatofPoint 
     MatOfPoint point = new MatOfPoint(approxCurve.toArray()); 

     //get boundingrect from contour 
     Rect rect = Imgproc.boundingRect(point); 

     Imgproc.rectangle(mRgba,new Point(rect.x, rect.y), new Point(rect.x + rect.width, rect.y + rect.height), new Scalar(255, 0, 0, 255),3); 
     //bisa Imgproc.rectangle(mRgba, rect.tl(), rect.br(), new Scalar(255, 0, 0),1, 8,0); 


     //show contour kontur 
     if(Imgproc.contourArea(contours.get(contourIdx))>100) { 
      Imgproc.drawContours(mRgba, contours, contourIdx, new Scalar(0,255,0), 5); 
     } 
    } 
    return mRgba; 

希望，有人在这一些经验。谢谢..

Answer 1

使用功能Imgproc.contourArea只需简单地找到所有轮廓的区域，最大面积的轮廓就是最大的区域。

代码绘制最大的轮廓会是这样：

double maxVal = 0; 
int maxValIdx = 0; 
for (int contourIdx = 0; contourIdx < contours.size(); contourIdx++) 
{ 
    double contourArea = Imgproc.contourArea(contours.get(contourIdx)); 
    if (maxVal < contourArea) 
    { 
     maxVal = contourArea; 
     maxValIdx = contourIdx; 
    } 
} 

Imgproc.drawContours(mRgba, contours, maxValIdx, new Scalar(0,255,0), 5);