Check Checkerboard Corners by thewoz · Pull Request #24546 · opencv/opencv

thewoz · 2023-11-15T12:46:13Z

What I did was get you to pull out of findChessboardCorners cornres the whole part that "checks" and sorts the corners of the checkerboard if present.
The main reason for this is that findChessboardCorners is often very slow to find the corners and this depends in that the size the contrast etc of the checkerboards can be very different from each other and writing a function that works on all kinds of images is complicated.
So I find it very useful to have the ability to write your own code to process the image and then have a function that controls or orders the corners.

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

I agree to contribute to the project under Apache 2 License.
To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
The PR is proposed to the proper branch
There is a reference to the original bug report and related work
There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
The feature is well documented and sample code can be built with the project CMake

asmorkalov · 2023-11-16T05:38:36Z

Some test is required for the new function.

thewoz · 2023-11-16T06:59:23Z

sure what kind of test do you think would be good? But do you mean a permanent test to put in the opencv tests or a test just to check that it works?

asmorkalov · 2023-11-16T14:24:03Z

I mean regular unit test. You can re-use some images from findChessboardCorners tests. Also checkChessboardCorners sounds misleading. I propose something like findChessboardCornersSimple, because, it's not chessboard validation.

thewoz · 2023-11-16T14:50:56Z

ok sound good for me.

thewoz · 2023-11-16T21:16:58Z

sorry but I'm not able to find the images used in the findChessboardCornes test

AleksandrPanov · 2023-11-17T07:17:28Z

may relate to "cv2.findChessboardCorners() running endlessly on certain images #23558" issue

thewoz · 2023-11-17T12:03:02Z

Hi, I may as well test on image #23558 but the result will depend on how I binarize the image before calling the proposed function.
Aren't there already some checkerboard images I can use as a test? If I can add some.

thewoz · 2023-11-20T15:35:36Z

@asmorkalov sorry where I can find the findChessboardCorners test images?

asmorkalov · 2023-11-20T19:35:50Z

https://github.com/opencv/opencv_extra/tree/4.x/testdata/cv/cameracalibration

thewoz · 2023-11-20T22:24:53Z

Hi,
I have test the pull request against the images:
BoardStereoL1-6.png BoardStereoR1-6.png and chess1-6.png

in

https://github.com/opencv/opencv_extra/tree/4.x/testdata/cv/cameracalibration

and the chessboard was found in each of them.

asmorkalov · 2023-11-21T06:23:11Z

Hello @thewoz . Thanks a lot for the contribution! The PR and API change was discussed on OpenCV Core team meeting. Team members propose to not introduce the new function, but add flag to findChessboardCorners and presume single entry point. As alternative, it could be a combination of existing flags and some new one. For example, if you introduce some new flag to force max_dilations=0 and disable CALIB_CB_FAST_CHECK, CALIB_CB_NORMALIZE_IMAGE, CALIB_CB_ADAPTIVE_THRESH you get almost the same you what.

This reverts commit 0911e2f.

thewoz · 2023-11-21T13:06:03Z

Hi @asmorkalov thanks to you and to all the team.
I understand your point and have proceeded to add a new flag.
I have named it CALIB_CB_PLAIN. What it actually does is to ignore the other flags and set max_dilations to zero as suggested.

thewoz · 2023-12-01T10:45:53Z

Hi there is anything else I can do ?

asmorkalov

👍

asmorkalov · 2023-12-01T10:48:06Z

@vpisarev @mshabunin Please take a look too.

modules/calib3d/src/calibinit.cpp

modules/calib3d/include/opencv2/calib3d.hpp

modules/calib3d/src/calibinit.cpp

mshabunin

I think we need a test for this new flag, something simple - load one of the test images with QR code, manually do threshold, dilate and other preparations, call function and expect detection result. Also a test for exception for BGR image input.

mshabunin · 2023-12-01T18:36:48Z

modules/calib3d/src/calibinit.cpp

    SHOW("New binarization", thresh_img_new);

-    if (flags & CALIB_CB_FAST_CHECK)
+    if (flags & CALIB_CB_FAST_CHECK && !(flags & CALIB_CB_PLAIN))


Suggested change

if (flags & CALIB_CB_FAST_CHECK && !(flags & CALIB_CB_PLAIN))

if (flags & CALIB_CB_FAST_CHECK && !is_plain)

BTW, wouldn't it be useful to have both PLAIN and FAST_CHECK flags enabled?

Hi mshabunin I'm not so sure about the idea of having both CALIB_CB_PLAIN and CALIB_CB_FAST_CHECK active at the same time.
The basic idea with CALIB_CB_PLAIN is to have a function that in fact does "nothing" in the sense that all image processing (binarization) is done externally

modules/calib3d/src/calibinit.cpp

thewoz · 2023-12-01T21:20:56Z

I think we need a test for this new flag, something simple - load one of the test images with QR code, manually do threshold, dilate and other preparations, call function and expect detection result. Also a test for exception for BGR image input.

Where do you think is the best place to put these tests?

mshabunin · 2023-12-02T15:17:35Z

Perhaps here: https://github.com/opencv/opencv/blob/4.x/modules/calib3d/test/test_chesscorners.cpp or in one of neighbour files.

thewoz · 2023-12-04T10:59:28Z

I added the first test.
I relied on an existing one.
I did not run all the tests because for each one you would have to do a different binarization.
I think anyway they can be enough

thewoz · 2023-12-14T08:37:53Z

is there anything else i can do?

modules/calib3d/src/calibinit.cpp

asmorkalov · 2023-12-20T12:58:09Z

@vpisarev @mshabunin May I merge the patch?

Check Checkerboard Corners opencv#24546 What I did was get you to pull out of findChessboardCorners cornres the whole part that "checks" and sorts the corners of the checkerboard if present. The main reason for this is that findChessboardCorners is often very slow to find the corners and this depends in that the size the contrast etc of the checkerboards can be very different from each other and writing a function that works on all kinds of images is complicated. So I find it very useful to have the ability to write your own code to process the image and then have a function that controls or orders the corners. See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request - [x] I agree to contribute to the project under Apache 2 License. - [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV - [x] The PR is proposed to the proper branch - [ ] There is a reference to the original bug report and related work - [ ] There is accuracy test, performance test and test data in opencv_extra repository, if applicable Patch to opencv_extra has the same branch name. - [ ] The feature is well documented and sample code can be built with the project CMake

thewoz added 2 commits November 15, 2023 13:38

update

e063758

Update calibinit.cpp

f5ec9b1

asmorkalov added feature category: calib3d pr: needs test New functionality requires minimal tests set labels Nov 16, 2023

rename

afb6afe

fix issue 23558

0911e2f

thewoz added 2 commits November 21, 2023 13:14

Revert "fix issue 23558"

12ebe1f

This reverts commit 0911e2f.

remove findChessboardCornersSimple() and add flag CALIB_CB_PLAIN

e68178b

remove trailing whitespace

26933f6

asmorkalov approved these changes Dec 1, 2023

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asmorkalov requested review from mshabunin and vpisarev December 1, 2023 10:48

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asmorkalov merged commit e64c5dc into opencv:4.x Dec 20, 2023

asmorkalov mentioned this pull request Jan 19, 2024

5.x merge 4.x #24862

Merged

	if (flags & CALIB_CB_FAST_CHECK && !(flags & CALIB_CB_PLAIN))
	if (flags & CALIB_CB_FAST_CHECK && !is_plain)

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