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This article will explain in detail how to achieve contour matching based on Hu moments in OpenCV. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

First, find the outline

Original drawing

Test pattern

VectorfindContour (Mat Image) {Mat gray; cvtColor (Image, gray, COLOR_BGR2GRAY); Mat thresh; threshold (gray, thresh, 0,255, THRESH_BINARY_INV | THRESH_OTSU); vectorcontours; findContours (thresh, contours, RETR_EXTERNAL, CHAIN_APPROX_NONE); vectorEffectConts; for (int I = 0; I

< contours.size(); i++) { double area = contourArea(contours[i]); if (area >

1000) {EffectConts.push_back (contours [I]);}} return EffectConts;}

As shown in the figure, this is the outermost outline found. Next, we match based on the contour.

Second, calculate the Hu moment

OpenCV provides moments API to calculate the center moment of the image; HuMoments API is used to calculate the Hu moment. Please find out the relevant knowledge about moments HuMoments by yourself.

Moments m_test = moments (test_contours [0]); Mat hu_test; HuMoments (m_test, hu_test); double MinDis = 1000; int MinIndex = 0; for (int I = 0; I

< src_contours.size(); i++) { Moments m_src = moments(src_contours[i]); Mat hu_src; HuMoments(m_src, hu_src); double dist = matchShapes(hu_test, hu_src, CONTOURS_MATCH_I1, 0); if (dist < MinDis) { MinDis = dist; MinIndex = i; } } 上面代码段大致思路是：首先计算测试图的Hu矩；然后使用一个for循环计算原图中所有轮廓的Hu矩，依次计算两Hu矩的相似程度。在这里使用matchShapes API计算两个Hu矩。函数返回值代表两Hu矩的相似程度。完全相同返回值为0。即这里通过计算两Hu矩的相似程度，找到返回值最小的那个作为成功匹配。 三、显示效果 drawContours(src, src_contours, MinIndex, Scalar(0, 255, 0), 2); Rect rect = boundingRect(src_contours[MinIndex]); rectangle(src, rect, Scalar(0, 0, 255), 2); 最终效果如图所示。 四、源码#include#includeusing namespace std;using namespace cv;vectorfindContour(Mat Image){ Mat gray; cvtColor(Image, gray, COLOR_BGR2GRAY); Mat thresh; threshold(gray, thresh, 0, 255, THRESH_BINARY_INV | THRESH_OTSU); vectorcontours; findContours(thresh, contours, RETR_EXTERNAL, CHAIN_APPROX_NONE); vectorEffectConts; for (int i = 0; i < contours.size(); i++) { double area = contourArea(contours[i]); if (area >

1000) {EffectConts.push_back (contours [I]);} return EffectConts;} int main () {Mat src = imread ("test/hand.jpg"); Mat test = imread ("test/test-3.jpg"); if (src.empty () | | test.empty ()) {cout

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