OpenCV drawMatches——queryIdx 和 trainIdx

问题描述

这是 OpenCV 的 drawMatches() 函数:p>

This is OpenCV's drawMatches() function:

void drawMatches(Mat img1, vector<KeyPoint> keypoints1,
                 Mat img2, vector<KeyPoint> keypoints2,
                 vector<DMatch> matches, 
                 Mat outImg) //want keypoints1[i] = keypoints2[matches[i]]

请注意，matches 属于 vector 类型.这是 DMatch 构造函数:

Notice that matches is of type vector<DMatch>. Here is the DMatch constructor:

DMatch(int queryIdx, int trainIdx, float distance)

据推测，queryIdx 是一组关键点的索引，trainIdx 是另一组关键点的索引.

Presumably, queryIdx is an index into one set of keypoints, and trainIdx is an index into the other set of keypoints.

问题:queryIdx 索引到 keypoints1 是否真的，而 trainIdx 索引到 keypoints2?或者，是否反过来?

The question: Is it true that queryIdx indexes into keypoints1, and trainIdx indexes into keypoints2? Or, is it the other way around?

推荐答案

这取决于你如何获得 matches.

That depends on how you get matches.

如果按顺序调用匹配函数:

If you call match function in the order:

match(descriptor_for_keypoints1, descriptor_for_keypoints2, matches)

那么queryIdx指keypoints1，trainIdx指keypoints2，反之亦然.

then queryIdx refers to keypoints1 and trainIdx refers to keypoints2, or vice versa.

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