流域邊界緊密圍繞一個區域

我想在OpenCV中創建兩個Blob的平均值。爲了實現這一目標，我打算以下列方式預處理的圖像上使用分水嶺算法：流域邊界緊密圍繞一個區域

cv::Mat common, diff, processed, result; 
cv::bitwise_and(blob1, blob2, common); //calc common area of the two blobs 
cv::absdiff(blob1, blob2, diff);  //calc area where they differ 

cv::distanceTransform(diff, processed, CV_DIST_L2, 3); //idea here is that the highest intensity 
                 //will be in the middle of the differing area 
cv::normalize(processed, processed, 0, 255, cv::NORM_MINMAX, CV_8U); //convert floats to bytes 

cv::Mat watershedMarkers, watershedOutline; 
common.convertTo(watershedMarkers, CV_32S, 1./255, 1); //change background to label 1, common area to label 2 
watershedMarkers.setTo(0, processed); //set 0 (unknown) for area where blobs differ 

cv::cvtColor(processed, processed, CV_GRAY2RGB); //watershed wants 3 channels 
cv::watershed(processed, watershedMarkers); 
cv::rectangle(watershedMarkers, cv::Rect(0, 0, watershedMarkers.cols, watershedMarkers.rows), 1); //remove the outline 

//draw the boundary in red (for debugging) 
watershedMarkers.convertTo(watershedOutline, CV_16S); 
cv::threshold(watershedOutline, watershedOutline, 0, 255, CV_THRESH_BINARY_INV); 
watershedOutline.convertTo(watershedOutline, CV_8U); 
processed.setTo(cv::Scalar(CV_RGB(255, 0, 0)), watershedOutline); 

//convert computed labels back to mask (blob), less relevant but shows my ultimate goal 
watershedMarkers.convertTo(watershedMarkers, CV_8U); 
cv::threshold(watershedMarkers, watershedMarkers, 1, 0, CV_THRESH_TOZERO_INV); 
cv::bitwise_not(watershedMarkers * 255, result);

我的結果問題是，計算出的邊界是（幾乎）總是毗鄰常見的兩種斑點的面積。下面是圖片：

輸入標記（黑= 0，灰色= 1，白色= 2）

流域輸入圖像（距離變換結果）用得到的輪廓在紅色得出：

我期望邊界沿着輸入的最大強度區域（即沿着不同區域的中間）。相反（正如你所看到的），它主要圍繞標記爲2的區域，稍稍移動以觸摸背景（標記爲1）。我在這裏做錯了什麼，或者我誤解了分水嶺是如何工作的？

來源

2017-02-09 slawekwin

見[此]（http://stackoverflow.com/questions/31961240/opencv-watershed-segmentation-miss-some-objects?rq=1） –

@JeruLuke感謝，但不是這樣。我的背景具有標籤1和對象2. – slawekwin

反轉距離變換，使距離較遠的點具有較小的值。在'normalize'行之後加上'processed = 255 - processed'。 – Miki

從這一形象開始：

你可以得到正確的結果只是傳遞一個全零圖像分水嶺算法。所述「盆」然後同樣填充的「水」從每個開始「側面」（然後只記得，以除去其由缺省通過分水嶺算法設置爲-1外邊界）：

代碼：

#include <opencv2\opencv.hpp> 

using namespace cv; 
using namespace std; 

int main() 
{ 
    Mat1b img = imread("path_to_image", IMREAD_GRAYSCALE); 

    Mat1i markers(img.rows, img.cols, int(0)); 
    markers.setTo(1, img == 128); 
    markers.setTo(2, img == 255); 

    Mat3b image(markers.rows, markers.cols, Vec3b(0,0,0)); 
    markers.convertTo(markers, CV_32S); 
    watershed(image, markers); 

    Mat3b result; 
    cvtColor(img, result, COLOR_GRAY2BGR); 
    result.setTo(Scalar(0, 0, 255), markers == -1); 

    imshow("Result", result); 
    waitKey(); 

    return(0); 
}

來源

2017-02-09 13:52:16 Miki

流域邊界緊密圍繞一個區域

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