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Merge pull request #28227 from dheeraj25406:docs-moments-degenerate

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docs(imgproc): clarify cv::moments behavior for degenerate contours #28227

relates to https://github.com/opencv/opencv/issues/28222
Clarifies that for degenerate contours (single point or collinear points),
cv::moments() returns m00 == 0 and centroid is undefined.
Documents common workarounds such as boundingRect center or point averaging.
This commit is contained in:
Dheeraj Alamuri
2025-12-23 23:23:43 +05:30
committed by GitHub
parent 4705320496
commit d3c539bf71
2 changed files with 27 additions and 0 deletions
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12
modules/imgproc/include/opencv2/imgproc.hpp
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@@ -3876,6 +3876,18 @@ used for images only.
@note Only applicable to contour moments calculations from Python bindings: Note that the numpy
type for the input array should be either np.int32 or np.float32.
@note For contour-based moments, the zeroth-order moment \c m00 represents
the contour area.
If the input contour is degenerate (for example, a single point or all points
are collinear), the area is zero and therefore \c m00 == 0.
In this case, the centroid coordinates (\c m10/m00, \c m01/m00) are undefined
and must be handled explicitly by the caller.
A common workaround is to compute the center using cv::boundingRect() or by
averaging the input points.
@sa contourArea, arcLength
*/
CV_EXPORTS_W Moments moments( InputArray array, bool binaryImage = false );

15
modules/imgproc/test/test_contours.cpp
View File

@@ -593,5 +593,20 @@ TEST(Imgproc_PointPolygonTest, regression_10222)
EXPECT_GT(result, 0) << "Desired result: point is inside polygon - actual result: point is not inside polygon";
}
TEST(Imgproc_Moments, degenerateContours)
{
std::vector<cv::Point> c1;
c1.push_back(cv::Point(10,10));
cv::Moments m1 = cv::moments(c1, false);
EXPECT_EQ(m1.m00, 0);
std::vector<cv::Point> c2;
c2.push_back(cv::Point(0,0));
c2.push_back(cv::Point(5,5));
c2.push_back(cv::Point(10,10));
cv::Moments m2 = cv::moments(c2, false);
EXPECT_EQ(m2.m00, 0);
}
}} // namespace
/* End of file. */