samples: add color-coded bounding boxes for multi QR code detection #29281
Improves the existing qrcode.py sample by adding color-coded bounding boxes when multiple QR codes are detected simultaneously.
Previously all QR codes were drawn with the same green color, making it hard to distinguish between them visually.
This change adds a QR_COLORS palette so each detected QR code gets a unique color, improving visual clarity for multi-QR detection.
Co-authored-by: Ayush Gupta <gupta.ayushg@gmail.com>
Enable collectContours in detect_blob.cpp and draw the per-blob
contours returned by getBlobContours(), so the sample exercises the
public contour-collection API added in #21942.
Refs #25904
Update ArUco doc #28824
See https://github.com/opencv/opencv/pull/28823
Update of the ArUco doc but targeted for OpenCV 4.
### Pull Request Readiness Checklist
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Fix regex escape warning in _coverage.py by using raw string #2819
while i am running '_coverage.py' I noticed there is a syntax warning:"\." It is an invalid escape sequence
The regex was written as a normal string with '\.' which is not valid escape in string literals and give problems and error in a new python versions.
To fix this switch to raw string(r'cv2?\.\w+') which can passes the backslashes directly to the regex engine. This removes the warning and keeps the code and pattern working properly.
This is a small fix but important for future compatibilities.
docs(js): Fix Mat.clone() documentation to use mat_clone() for deep copy #27985
- Update code example to use ```mat_clone()``` instead of ```clone()```
- Add explanatory note about shallow copy issue due to Emscripten embind
Problem
- OpenCV.js documentation shows ```Mat.clone()``` usage, but this method performs shallow copy instead of deep copy due to Emscripten embind limitations, causing unexpected behavior where modifications to cloned matrices affect the original.
Related Issues and PRs
- Fixes documentation aspect of issue #27572
- Related to PR #26643 (js_clone_fix)
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2025-10-14T05:53:31.5387050Z C:\GHA-OCV-1\_work\ci-gha-workflow\ci-gha-workflow\opencv\modules\imgcodecs\src\bitstrm.cpp(156,57): warning C4244: 'argument': conversion from 'int64_t' to 'ptrdiff_t', possible loss of data [C:\GHA-OCV-1\_work\ci-gha-workflow\ci-gha-workflow\build\modules\imgcodecs\opencv_imgcodecs.vcxproj]
### Pull Request Readiness Checklist
Optional Known Foreground Mask for Background Subtractors #27810
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request
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### Description
This adds an optional foreground input mask parameter to the MOG2 and KNN background subtractors, in line with issue https://github.com/opencv/opencv/issues/26476
4 tests are added under test_bgfg2.cpp:
2 for each subtractor type (1 with shadow detection and 1 without)
A demo shows the feature with only 3 parameters and with a 4th optional foreground mask for both core subtractor types.
Note: To patch contrib inheritance of the background subtraction class, empty apply method which throws a not implemented error is added to contrib subclasses. This is done to keep the overloaded apply function as pure virtual. Contrib PR to be made and linked shortly.
Contrib Repo Paired Pull Request: https://github.com/opencv/opencv_contrib/pull/4017
Add Raspberry Pi 4 and 5 V4L2 Stateless HEVC Hardware Acceleration with FFmpeg #27453
This PR enables V4L2 stateless HEVC hardware acceleration for Raspberry Pi 5 within OpenCV's videoio module. It leverages FFmpeg's drm acceleration ([FFmpeg API changes](https://github.com/FFmpeg/FFmpeg/blob/ee1f79b0fa4c82da9c19328b049b593c71611402/doc/APIchanges#L1529)), significantly improving HEVC decoding performance on RPi5 for robotics and embedded vision applications.
I have a working proof-of-concept with local benchmarks showing clear gains.
Checklist Status:
Ready: License, branch (4.x), FFmpeg reference, and (linked) related issue (#27452).
Seeking Guidance: Need help with formal C++ performance/accuracy tests, opencv_extra integration, and full documentation/examples.
As a Python developer, I welcome C++ best practice feedback and assistance with testing setup.
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The Kullback-Leibler divergence works with histogram that have integral = 1,
otherwise it can return negative values. The normalization of the histograms
have been changed accordingly, and all the six comparison methods have been
used in the histogram comparison tutorial.
Fix Typos in Comments and Documentation #27455
Description:
This pull request corrects minor typos in comments and documentation within the codebase:
- Replaces "representitive" with "representative" in kmeans.cpp.
- Replaces "indices" with the correct spelling in a comment in main.cu.
Fix Typos in Comments and Error Messages Across Multiple Files #27434
Description:
This pull request corrects several typographical errors in comments and error messages in the following files:
- `samples/directx/d3d11_interop.cpp`: Fixed typo in the error message ("betweem" → "between").
- `samples/dnn/yolo_detector.cpp`: Fixed typo in a comment ("elemets" → "elements").
- `samples/winrt/ImageManipulations/MediaExtensions/OcvTransform.cpp`: Fixed typo in a comment ("peferred" → "preferred").
These changes improve code readability and maintain consistency in documentation and error reporting. No functional code was modified.
Fix NaNs in HDR Triangle Weights and Tonemapping and Update LDR Ground Truth in tutorial #27396
The PR closes#27392
Updated the triangle weights to use a small epsilon value instead of zero to prevent NaN issues in HDR processing.
Also fixed a float-to-double division issue by explicitly casting double values to float, which was previously producing garbage values and leading to NaNs in tonemapping.
The current LDR ground truth image used in the tutorial [ldr.png](https://github.com/opencv/opencv/blob/4.x/doc/tutorials/others/images/ldr.png) was originally generated using TonemapDurand (check this commit https://github.com/opencv/opencv/commit/833f8d16fab5e57c5e800a55fa0fb08c7a31c3b1), which was moved to opencv_contrib a long time ago in this commit: https://github.com/opencv/opencv/commit/742f22c09bd0c27b450f141bc984f280c8cde98e. However, the current Tonemap implementation in OpenCV main only performs normalization and gamma correction, which produces noticeably different results. This PR updates the LDR grouth truth image in tutorial with the result of TonemapDrago, and tutorials to use TonemapDrago as Tonemap gives a darker image.
Tonemap output:
TonemapDrago output:
### Pull Request Readiness Checklist
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Replaced sprintf with snprintf #26815
Fixes : #26814
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Feature: weighted Hough Transform #21407
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AndroidMediaNdkVideoWriter pixel format enhancement #26698
* videoio(Android): Add source pixel formats RGBA and GRAY to AndroidMediaNdkVideoWriter
Let AndroidMediaNdkVideoWriter::write() deduce source pixel format from matrix type:
CV_8UC3 -> BGR (as before)
CV_8UC4 -> RGBA (use in conjunction with CvCameraViewFrame)
CV_8UC1 -> GRAY
* samples/android/video-recorder: Send images to VideoWriter in RGBA format
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AndroidMediaNdkCapture pixel format enhancement #26656
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Animated WebP Support #25608
related issues #24855#22569
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Alexander Smorkalov
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