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js: restore deep copy behavior for Mat.clone()#28216

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asmorkalov merged 2 commits intoopencv:4.xfrom
happy-capybara-man:4.x
Dec 22, 2025
Merged

js: restore deep copy behavior for Mat.clone()#28216
asmorkalov merged 2 commits intoopencv:4.xfrom
happy-capybara-man:4.x

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@happy-capybara-man happy-capybara-man commented Dec 17, 2025 •
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Problem

In OpenCV.js, cv.Mat.clone() may resolve to Embind ClassHandle.clone() (handle/shallow clone) instead of OpenCV deep copy.

Changes

  • modules/js/src/helpers.js: override cv.Mat.prototype.clone -> mat_clone after runtime init
  • modules/js/test/test_mat.js: update/extend tests to validate deep copy semantics of clone()

Fixes #27572
Related: PR #26643 (js_clone_fix), PR #27985 (documentation update)

Verification

  • Built OpenCV.js with Emscripten 2.0.10
  • QUnit: bin/tests.html
  • CoreMat: test_mat_creation (0 failures)
clone_fix

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

@happy-capybara-man
js: restore deep copy behavior for Mat.clone()
8ea50a7 
Emscripten 3.1.71+ introduced ClassHandle.clone() which performs a shallow copy.
This shadowed the original OpenCV clone() method which was intended for deep copying.

This patch:
1. Hooks into onRuntimeInitialized in helpers.js
2. Overrides cv.Mat.prototype.clone to point to mat_clone (deep copy)
3. Updates JS tests to use clone() to verify the fix
@asmorkalov asmorkalov requested a review from vrabaud December 18, 2025 06:59
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vrabaud commented Dec 18, 2025

I think it makes sense. Users will no more about OpenCV that emscripten and will therefore expect clone to behave like in C++. LGTM

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happy-capybara-man commented Dec 18, 2025

Thanks for the review! I've removed the extra blank line at the end of helpers.js

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happy-capybara-man commented Dec 20, 2025

@asmorkalov Hi, the CI seems to have failed due to network issues. Could you please help re-run the failed jobs? I'm hoping to include this in a report due this Tuesday. Thanks for your help!!

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happy-capybara-man commented Dec 22, 2025

@asmorkalov Apologies for the extra notification.

I just wanted to flag that the CI re-run unfortunately hit the same Windows infrastructure error (EBUSY).

Since this is blocking the merge and my reporting deadline is tomorrow (Tuesday), I wanted to bring this to your attention one last time. I hope it's okay to ask for a merge based on the existing approval, given the CI instability.

Thanks again for your patience and help!

@asmorkalov asmorkalov added this to the 4.13.0 milestone Dec 22, 2025
@asmorkalov asmorkalov self-assigned this Dec 22, 2025
@asmorkalov asmorkalov merged commit 165b464 into opencv:4.x Dec 22, 2025
67 of 76 checks passed
@happy-capybara-man happy-capybara-man mentioned this pull request Dec 22, 2025
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@asmorkalov asmorkalov mentioned this pull request Feb 11, 2026
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@vrabaud vrabaud Awaiting requested review from vrabaud

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@asmorkalov asmorkalov

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category: javascript (js)

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4.13.0

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Successfully merging this pull request may close these issues.

最新版本4.12.x中，clone似乎成了浅拷贝，我不得不使用copyTo

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