如何使用OpenCV findContours查找图像中的区域？

Question

我在Android Studio中使用OpenCV。

我有一张白色背景和黑色区域的图像。在黑色区域，我有一些轮廓。我想检测黑色区域内的轮廓，如下所示：

但是我的代码没有用;相反，它将整个图像的边返回为轮廓：

我做错了什么？

public  Mat[] Smudge_detection(Mat color_mat)
{
    Mat lab_mat=new Mat();
    Imgproc.cvtColor(color_mat, lab_mat, Imgproc.COLOR_RGB2Lab);
    List<Mat> lab_list = new ArrayList(3);
    Core.split(lab_mat, lab_list);
    Mat eqHist=new Mat();

    Imgproc.equalizeHist(lab_list.get(0),eqHist);

    lab_list.set(0,eqHist);
    Core.merge(lab_list,lab_mat);
    Mat rgb_mat=new Mat();
    Mat gray_mat=new Mat();

    Imgproc.cvtColor(lab_mat,rgb_mat,Imgproc.COLOR_Lab2RGB);
    Imgproc.cvtColor(rgb_mat,gray_mat,Imgproc.COLOR_RGB2GRAY);

    MatOfInt histSize = new MatOfInt(256);
    MatOfInt channels=new MatOfInt(0);
    Mat hist_ = new Mat();
    MatOfFloat histRange = new MatOfFloat(0, 220);
    List<Mat>gray_lst= new ArrayList<Mat>(1);
    Core.split(gray_mat,gray_lst);
    Imgproc.calcHist(gray_lst,channels,new Mat(),hist_,histSize,histRange,false);                                  

    Core.MinMaxLocResult mml= Core.minMaxLoc(hist_);
    double tresh=mml.maxLoc.y;

    // for  remove white area around of black circle

    Mat thresh_mat=new Mat();
    Imgproc.threshold(gray_mat,thresh_mat,tresh,220,THRESH_BINARY);
    Mat notmat=new Mat();
    Core.bitwise_not(thresh_mat,notmat);

    Mat morph_mat=new Mat();
    Imgproc.morphologyEx(notmat,morph_mat,Imgproc.MORPH_CLOSE,  Imgproc.getStructuringElement(Imgproc.MORPH_ELLIPSE, new Size(2,2)));

    List<MatOfPoint> contours=new ArrayList<>();
    final Mat hierarchy = new Mat();
    Imgproc.findContours(morph_mat,contours,hierarchy,  Imgproc.RETR_EXTERNAL, Imgproc.CHAIN_APPROX_SIMPLE);
    Mat drawmat=color_mat.clone();
    Imgproc.drawContours(drawmat,contours,0,new Scalar(255,50,180),15);
    Mat[] out=new Mat[2];
    out[0]=contours.get(0);
    out[1]=drawmat.clone();

    return  out;
}

Answer 1

我在python中的结果，您可以参考：

图书馆正在关闭，我将......

这是我的python代码：

#!/usr/bin/python3
# 2017.10.08 21:48:13 CST

import cv2
import numpy as np

img = cv2.imread("t.png")
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
retval, threshed = cv2.threshold(gray, 127, 255, cv2.THRESH_BINARY)

_,contours,h = cv2.findContours(threshed, cv2.RETR_LIST, cv2.CHAIN_APPROX_SIMPLE)

dst1 = img.copy()
dst2 = img.copy()
cv2.drawContours(dst1, contours, -1, (0,255,0), 3)

cnts = []
for cnt in contours:
    rect = cv2.boundingRect(cnt)
    x,y,w,h = rect
    if w < 10 or h < 10 >>w > 100 or h > 100:
        continue
    cnts.append(cnt)

print(len(cnts))
cv2.drawContours(dst2, cnts, -1, (0,255,0), 3)

res = np.hstack((dst1, dst2))
cv2.imwrite("res.png", res)
cv2.imshow("res", res)
cv2.waitKey()
cv2.destroyAllWindows()