findContours() [1/2]
void cv::findContours (
InputArray image,
OutputArrayOfArrays contours, //輪廓
OutputArray hierarchy,//輪廓的拓撲結構
int mode, //
int method, //
Point offset = Point()
)
Python:
contours, hierarchy =cv.findContours(image, mode, method[, contours[, hierarchy[, offset]]])
#include <opencv2/imgproc.hpp>
Finds contours in a binary image.
The function retrieves contours from the binary image using the algorithm [216] . The contours are a useful tool for shape analysis and object detection and recognition. See squares.cpp in the OpenCV sample directory.
Note
Since opencv 3.2 source image is not modified by this function.
Parameters
image Source, an 8-bit single-channel image. Non-zero pixels are treated as 1’s. Zero pixels remain 0’s, so the image is treated as binary . You can use compare, inRange, threshold , adaptiveThreshold, Canny, and others to create a binary image out of a grayscale or color one. If mode equals to RETR_CCOMP or RETR_FLOODFILL, the input can also be a 32-bit integer image of labels (CV_32SC1).
contours Detected contours. Each contour is stored as a vector of points (e.g. std::vector<std::vectorcv::Point >).
hierarchy Optional output vector (e.g. std::vectorcv::Vec4i), containing information about the image topology. It has as many elements as the number of contours. For each i-th contour contours[i], the elements hierarchy[i][0] , hierarchy[i][1] , hierarchy[i][2] , and hierarchy[i][3] are set to 0-based indices in
contours of the next and previous contours at the same hierarchical level, the first child contour and the parent contour（在同一層級的下一個輪廓/上一個輪廓，第一個子輪廓，父輪廓）, respectively. If for the contour i there are no next, previous, parent, or nested contours, the corresponding elements of hierarchy[i] will be negative.
mode Contour retrieval mode, see RetrievalModes
method Contour approximation method, see ContourApproximationModes
offset Optional offset by which every contour point is shifted. This is useful if the contours are extracted from the image ROI and then they should be analyzed in the whole image context.
