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search in two directions when try to add new quad in addOuterQuad#25807

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asmorkalov merged 2 commits intoopencv:4.xfrom
spdfghi:4.x
Jul 24, 2024
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search in two directions when try to add new quad in addOuterQuad#25807
asmorkalov merged 2 commits intoopencv:4.xfrom
spdfghi:4.x

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@spdfghi spdfghi commented Jun 23, 2024 •
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In ChessBoardDetector::addOuterQuad, previous code try to connect new quad with inner quad, if possible, but only search for one direction. I have made three test images, one is normal(a.jpg), one lossed an outer quad(b.jpg), and then i flipped it vertically(c.jpg). Only last one fails. I fixed it by check two directions and row/col.

Here is the test code and images:

Mat img;
vector<Point2f> corners;
auto size = cv::Size(6, 6);
img = imread("D:/tmp/a.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
img = imread("D:/tmp/b.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
img = imread("D:/tmp/c.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";

a
a
b
b
c
c

@spdfghi spdfghi changed the title fixed bug: wrong implemention of connecting neighbor quad and new qua… search in two directions when try to add new quad in addOuterQuad Jun 24, 2024
@asmorkalov asmorkalov requested review from AleksandrPanov and asmorkalov and removed request for AleksandrPanov June 24, 2024 06:30
@asmorkalov asmorkalov added this to the 4.11.0 milestone Jun 24, 2024
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spdfghi commented Jun 27, 2024 •
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Since it's not an usual algorithm, so i have made a simple note image to show how it happends:
IMG_0039
i noted the index of missed quad, the privous code try to get another quad connected to the missed quad by first search the index prev_i quad, and then get the index next_i quad of prev_i quad. It works sometime, for example, A to C. However, it failed with the opposite direction, i.e., C to A. Which depends on who was first searched by dfs previously. The line begin in 1155 i made was followed line 924

for (int i = 0; i < 4; i++)
{
    CV_DbgAssert(q);
    ChessBoardQuad* neighbor = q->neighbors[i];
    switch (i)   // adjust col, row for this quad
    {           // start at top left, go clockwise
    case 0:
        row--; col--; break;
    case 1:
        col += 2; break;
    case 2:
        row += 2;   break;
    case 3:
        col -= 2; break;
    }

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asmorkalov commented Jul 2, 2024

@MaximSmolskiy Could you take a look and try with your dataset?

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asmorkalov commented Jul 19, 2024

@MaximSmolskiy Could you take a look and try with your dataset?

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MaximSmolskiy commented Jul 21, 2024

@MaximSmolskiy Could you take a look and try with your dataset?

@asmorkalov I didn't deal with this function, so I amn't ready to review this pr.
These changes provide minor improvements on my 2 private datasets:

  1. 294 -> 296 detected chessboards
  2. 524 -> 527 detected chessboards

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asmorkalov commented Jul 22, 2024

@MaximSmolskiy Thanks a lot for the feedback. The patch does not change result of synthetic benchmark. Just want to get feedback for real images.

@asmorkalov asmorkalov self-assigned this Jul 24, 2024
@asmorkalov asmorkalov merged commit 160879c into opencv:4.x Jul 24, 2024
@asmorkalov asmorkalov mentioned this pull request Jul 25, 2024
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fengyuentau pushed a commit to fengyuentau/opencv that referenced this pull request Aug 15, 2024
@spdfghi @fengyuentau
Merge pull request opencv#25807 from spdfghi:4.x
80581d6 
Search in two directions when try to add new quad in addOuterQuad opencv#25807

In ChessBoardDetector::addOuterQuad, previous code try to connect new quad with inner quad, if possible, but only search for one direction. I have made  three test images, one is normal(a.jpg), one lossed an outer quad(b.jpg), and then i flipped it vertically(c.jpg). Only last one fails. I fixed it by check two directions and row/col.

Here is the test code and images:
```
Mat img;
vector<Point2f> corners;
auto size = cv::Size(6, 6);
img = imread("D:/tmp/a.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
img = imread("D:/tmp/b.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
img = imread("D:/tmp/c.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
```
![a](https://github.com/opencv/opencv/assets/92856207/0dc7f5bf-7637-4333-9a9f-ec4ede790027)
a
![b](https://github.com/opencv/opencv/assets/92856207/39793485-ca0c-44c0-b44d-a593d36c1888)
b
![c](https://github.com/opencv/opencv/assets/92856207/2e7789c8-cfa5-438c-9530-2862a8a3741f)
c
thewoz pushed a commit to CobbsLab/OPENCV that referenced this pull request Feb 13, 2025
@spdfghi @thewoz
Merge pull request opencv#25807 from spdfghi:4.x
9a10e56 
Search in two directions when try to add new quad in addOuterQuad opencv#25807

In ChessBoardDetector::addOuterQuad, previous code try to connect new quad with inner quad, if possible, but only search for one direction. I have made  three test images, one is normal(a.jpg), one lossed an outer quad(b.jpg), and then i flipped it vertically(c.jpg). Only last one fails. I fixed it by check two directions and row/col.

Here is the test code and images:
```
Mat img;
vector<Point2f> corners;
auto size = cv::Size(6, 6);
img = imread("D:/tmp/a.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
img = imread("D:/tmp/b.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
img = imread("D:/tmp/c.jpg", 0);
std::cout<<cv::findChessboardCorners(img, size, corners)<<"\n";
std::cout << corners.size() << "\n";
```
![a](https://github.com/opencv/opencv/assets/92856207/0dc7f5bf-7637-4333-9a9f-ec4ede790027)
a
![b](https://github.com/opencv/opencv/assets/92856207/39793485-ca0c-44c0-b44d-a593d36c1888)
b
![c](https://github.com/opencv/opencv/assets/92856207/2e7789c8-cfa5-438c-9530-2862a8a3741f)
c
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@spdfghi @asmorkalov @MaximSmolskiy