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It is the first time I worked with ArUco markers and was disappointed by weird distortion after perspective transformation based on recognized markers. I assumed that its because of camera calibration errors and decided to test with "ideal" markers.

I calibrated camera with pattern file (not printed and photographed, but just from a source file). Then I generated my marker and put it on JPG image without any distortions. My program found the marker, I generated new position for marked and warped the image:

    int side = 100;
    resultCorners.push_back(corners[0][0]);
    resultCorners.push_back(Point2f(corners[0][0].x + side, corners[0][0].y));
    resultCorners.push_back(Point2f(corners[0][0].x + side, corners[0][0].y + side));
    resultCorners.push_back(Point2f(corners[0][0].x, corners[0][0].y + side));
    Mat w = getPerspectiveTransform(corners[0], resultCorners);
    warpPerspective(img_copy, result, w, img_copy.size());

That worked OK: 1.PNG

Then I minimized source image with one pyrDown call and tried to recognize marker again:

2.PNG

Could you please explain, why this weird distortion happens?

It is the first time I worked with ArUco markers and was disappointed by weird distortion after perspective transformation based on recognized markers. I assumed that its because of camera calibration errors and decided to test with "ideal" markers.

I calibrated camera with pattern file (not printed and photographed, but just from a source file). Then I generated my marker and put it on JPG image without any distortions. My program found the marker, I generated new position for marked and warped the image:

    int side = 100;
    resultCorners.push_back(corners[0][0]);
    resultCorners.push_back(Point2f(corners[0][0].x + side, corners[0][0].y));
    resultCorners.push_back(Point2f(corners[0][0].x + side, corners[0][0].y + side));
    resultCorners.push_back(Point2f(corners[0][0].x, corners[0][0].y + side));
    Mat w = getPerspectiveTransform(corners[0], resultCorners);
    warpPerspective(img_copy, result, w, img_copy.size());

That worked OK: 1.PNG

Then I minimized source image with one pyrDown call and tried to recognize marker again:

2.PNG

Could you please explain, why this weird distortion happens?happens and how I can avoid it in real situation with photo or video stream?

It is the first time I worked with ArUco markers and was disappointed by weird distortion after perspective transformation based on recognized markers. I assumed that its because of camera calibration errors and decided to test with "ideal" markers.

I calibrated camera with pattern file (not printed and photographed, but just from a source file). Then I generated my marker and put it on JPG image without any distortions. My program found the marker, I generated new position for marked and warped the image:

    int side = 100;
    resultCorners.push_back(corners[0][0]);
    resultCorners.push_back(Point2f(corners[0][0].x + side, corners[0][0].y));
    resultCorners.push_back(Point2f(corners[0][0].x + side, corners[0][0].y + side));
    resultCorners.push_back(Point2f(corners[0][0].x, corners[0][0].y + side));
    Mat w = getPerspectiveTransform(corners[0], resultCorners);
    warpPerspective(img_copy, result, w, img_copy.size());

That worked OK: 1.PNG

Then I minimized source image with one pyrDown call and tried to recognize marker again:

2.PNG

Could you please explain, why this weird distortion happens and how I can avoid it in real situation with photo or video stream?