流域边界紧密围绕一个区域
问题描述:
我想在OpenCV中创建两个Blob的平均值。为了实现这一目标,我打算以下列方式预处理的图像上使用分水岭算法:流域边界紧密围绕一个区域
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);
我的结果问题是,计算出的边界是(几乎)总是毗邻常见的两种斑点的面积。下面是图片:
我期望边界沿着输入的最大强度区域(即沿着不同区域的中间)。相反(正如你所看到的),它主要围绕标记为2的区域,稍稍移动以触摸背景(标记为1)。我在这里做错了什么,或者我误解了分水岭是如何工作的?
答
从这一形象开始:
你可以得到正确的结果只是传递一个全零图像分水岭算法。所述“盆”然后同样填充的“水”从每个开始“侧面”(然后只记得,以除去其由缺省通过分水岭算法设置为-1
外边界):
代码:
#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);
}
见[此](http://*.com/questions/31961240/opencv-watershed-segmentation-miss-some-objects?rq=1) –
@JeruLuke感谢,但不是这样。我的背景具有标签1和对象2. – slawekwin
反转距离变换,使距离较远的点具有较小的值。在'normalize'行之后加上'processed = 255 - processed'。 – Miki