查找并消除轮廓opencv

我正在研究一个程序，该程序可以提取拼图上的贴纸，然后再找到它们的RGB。目前，我正处于想要删除任何非“方形”的轮廓。我想知道我该如何做到这一点。查找并消除轮廓opencv

我所做的是我加载图像，灰色它，模糊它，canny边缘检测，扩大它找到轮廓，并绘制它们。

有没有办法绕着轮廓绘制而不是填充它们？并删除轮廓不是大致相同的大小或几乎90度的角度？

public static void main(String[] args) { 


     System.loadLibrary(Core.NATIVE_LIBRARY_NAME); 

     Mat capturedFrame = Imgcodecs.imread("first.png"); 

     //Gray 
     Mat gray = new Mat(); 
     Imgproc.cvtColor(capturedFrame, gray, Imgproc.COLOR_BGR2GRAY); 

     //Blur 
     Mat blur = new Mat(); 
     Imgproc.blur(gray, blur, new Size(3,3)); 
     //Canny image 
     Mat canny = new Mat(); 
     Imgproc.Canny(blur, canny, 20, 40, 3, true); 


     Imgcodecs.imwrite("test.png", canny); 

     //System.exit(0); 
     Mat kernel = Imgproc.getStructuringElement(1, new Size(3,3)); 
     Mat dilated = new Mat(); 
     Imgproc.dilate(canny,dilated, kernel); 


     List<MatOfPoint> contours = new ArrayList<>(); 
     //find contours 
     Imgproc.findContours(dilated, contours, new Mat(), Imgproc.RETR_TREE, Imgproc.CHAIN_APPROX_NONE); 
     //draw contours 

     Imgproc.cvtColor(capturedFrame, capturedFrame, Imgproc.COLOR_BGR2RGB); 
     for(int i = 0; i < contours.size(); i++){ 
      Imgproc.drawContours(capturedFrame, contours, i, new Scalar(0, 0, 255), -1); 
     } 


     Imgcodecs.imwrite("after.png", capturedFrame); 

     Imshow img = new Imshow("firstImg"); 

     img.show(capturedFrame); 

    }

这里是初始图像：