# \#opencvjs **URL:** https://forum.opencv.org/tag/opencvjs/65.md [Latest](https://forum.opencv.org/latest.md) · [Categories](https://forum.opencv.org/categories.md) · [Tags](https://forum.opencv.org/tags.md) --- ## [Introduction: Aspiring GSoC 2026 Contributor | Web Dev & Data Science](https://forum.opencv.org/t/introduction-aspiring-gsoc-2026-contributor-web-dev-data-science/24288)
**Author:** [@Yash\_Tajane](https://forum.opencv.org/u/Yash_Tajane)\ **Replies:** 0\ **Last updated:** [January 1, 2026, 4:54am UTC](https://forum.opencv.org/t/introduction-aspiring-gsoc-2026-contributor-web-dev-data-science/24288 "2026-01-01T04:54:46Z")
Hello OpenCV Community, My name is Yash Tajane. I am a student developer currently learning Web Development and Data Science. I am very interested in contributing to OpenCV for GSoC 2026. I am particularly fascinated b… --- ## [SIFT algorithm in opencvjs is undefined](https://forum.opencv.org/t/sift-algorithm-in-opencvjs-is-undefined/23973)
**Author:** [@2297098619pcz](https://forum.opencv.org/u/2297098619pcz)\ **Replies:** 5\ **Last updated:** [September 11, 2025, 10:03am UTC](https://forum.opencv.org/t/sift-algorithm-in-opencvjs-is-undefined/23973 "2025-09-11T10:03:50Z")
OpenCV version: 4.12.0 I added “‘SIFT’: \[‘create’\],” to features2d in opencv\_js.config.py. However, after building, references to cv.SIFT are still undefined. I also added the opencv\_contrib add-on module and enabled --… --- ## [Limitations of OpenCV on the browser?](https://forum.opencv.org/t/limitations-of-opencv-on-the-browser/23898)
**Author:** [@Recta\_al\_borween](https://forum.opencv.org/u/Recta_al_borween)\ **Replies:** 0\ **Last updated:** [August 25, 2025, 8:05am UTC](https://forum.opencv.org/t/limitations-of-opencv-on-the-browser/23898 "2025-08-25T08:05:09Z")
The official documentation writes OpenCV.js is a JavaScript binding for selected subset of OpenCV functions for the web platform. It allows emerging web applications with multimedia processing to benefit from the wide v… --- ## [Opencv.js cannot be compiled on Windows systems](https://forum.opencv.org/t/opencv-js-cannot-be-compiled-on-windows-systems/23334)
**Author:** [@jianxingyaoyjjwxy](https://forum.opencv.org/u/jianxingyaoyjjwxy)\ **Replies:** 2\ **Last updated:** [July 30, 2025, 11:39pm UTC](https://forum.opencv.org/t/opencv-js-cannot-be-compiled-on-windows-systems/23334 "2025-07-30T23:39:46Z")
I downloaded the latest versions of Emscripten, Python, Ninja, CMake, and OpenCV, and ran the following command emcmake python ./opencv/platforms/js/build\_js.py build\_js Error configure: python ./opencv/platforms/js/b… --- ## [How to pass parameters to Flann base matcher using Opencv JS](https://forum.opencv.org/t/how-to-pass-parameters-to-flann-base-matcher-using-opencv-js/21029)
**Author:** [@Borja\_Cano\_Barredo](https://forum.opencv.org/u/Borja_Cano_Barredo)\ **Replies:** 0\ **Last updated:** [May 16, 2025, 8:36am UTC](https://forum.opencv.org/t/how-to-pass-parameters-to-flann-base-matcher-using-opencv-js/21029 "2025-05-16T08:36:29Z")
Hi, After a lot of work trying to make flann matcher and sift to work on OpencvJS i finally have it working. Problem is i am trying to do feature matching for a streaming live cam in real-time and sift and flann are not… --- ## [\[OpenCV.js\] Getting SIFT and FLANN to work](https://forum.opencv.org/t/opencv-js-getting-sift-and-flann-to-work/9987)
**Author:** [@Digizard](https://forum.opencv.org/u/Digizard)\ **Replies:** 7\ **Last updated:** [May 14, 2025, 9:26am UTC](https://forum.opencv.org/t/opencv-js-getting-sift-and-flann-to-work/9987 "2025-05-14T09:26:11Z")
Hi, all! I’m looking for help on how to use SIFT and FLANN with OpenCV.js. I basically want to translate this code from Python: needle = cv.imread('needle.png', 0) haystack = cv.imread('haystack.png', 0) sift = cv.SIF… --- ## [ONNX Model with OpenCV.js](https://forum.opencv.org/t/onnx-model-with-opencv-js/14913)
**Author:** [@moritz](https://forum.opencv.org/u/moritz)\ **Replies:** 2\ **Last updated:** [February 10, 2025, 6:00am UTC](https://forum.opencv.org/t/onnx-model-with-opencv-js/14913 "2025-02-10T06:00:18Z")
Hey all, I have some issues using my ONNX model with OpenCV.js, which I trained with pytorch and then exported. The model runs fine with inference when I use the onnx runtime engine in python: import onnxruntime as or… --- ## [\[Opencv.js\] Loading tensorflow model into opencv.js](https://forum.opencv.org/t/opencv-js-loading-tensorflow-model-into-opencv-js/3422)
**Author:** [@eastemployeer](https://forum.opencv.org/u/eastemployeer)\ **Replies:** 6\ **Last updated:** [February 8, 2025, 6:55pm UTC](https://forum.opencv.org/t/opencv-js-loading-tensorflow-model-into-opencv-js/3422 "2025-02-08T18:55:26Z")
Hi there, I would like to ask whether there is any possibility to load tensorflow model (frozen\_inference\_graph.pb and corresponding .pbtxt file) into opencv.js? I’m struggling with it from several days. It appears that… --- ## [Building Opencv.js to include aruco and calib3d](https://forum.opencv.org/t/building-opencv-js-to-include-aruco-and-calib3d/19700)
**Author:** [@wanless](https://forum.opencv.org/u/wanless)\ **Replies:** 1\ **Last updated:** [January 6, 2025, 8:02pm UTC](https://forum.opencv.org/t/building-opencv-js-to-include-aruco-and-calib3d/19700 "2025-01-06T20:02:04Z")
Does anyone have a guild on how i can build Opencv.js to include aruco and calib3d when i try using cmake and emscripten im getting a dependency issue for ittnotify that i cant seem to get around. Any help is greatly ap… --- ## [ChArUco Calibration with OpenCV.js](https://forum.opencv.org/t/charuco-calibration-with-opencv-js/19527)
**Author:** [@sid220](https://forum.opencv.org/u/sid220)\ **Replies:** 1\ **Last updated:** [December 23, 2024, 11:34pm UTC](https://forum.opencv.org/t/charuco-calibration-with-opencv-js/19527 "2024-12-23T23:34:43Z")
I am trying to calibrate a camera with a ChArUco board in OpenCV.js. I can do the detection fine, but calibrateCameraCharuco does not exist in OpenCV.js. I tried adding it to platforms/js/opencv\_js.config.py like: objde… --- ## [How can avoid UMD header in opencv.js?](https://forum.opencv.org/t/how-can-avoid-umd-header-in-opencv-js/19433)
**Author:** [@kalwalt](https://forum.opencv.org/u/kalwalt)\ **Replies:** 0\ **Last updated:** [December 4, 2024, 9:07am UTC](https://forum.opencv.org/t/how-can-avoid-umd-header-in-opencv-js/19433 "2024-12-04T09:07:15Z")
As one of finale step in the opencv.js compilation, there is the make\_umd python script, that add this feature. But it’s possible to avoid this? --- ## [UndistortPoints() in opencv.js](https://forum.opencv.org/t/undistortpoints-in-opencv-js/19108)
**Author:** [@alxxn](https://forum.opencv.org/u/alxxn)\ **Replies:** 0\ **Last updated:** [October 24, 2024, 9:23pm UTC](https://forum.opencv.org/t/undistortpoints-in-opencv-js/19108 "2024-10-24T21:23:02Z")
Hi, I am wondering if anyone has a solution for undistorting points in opencv.js. From looking at this file opencv-js/src/types/opencv/calib3d.ts at main · TechStark/opencv-js · GitHub, I thought that cv.undistortPoints … --- ## [\[opencv.js\] support for findHomography()](https://forum.opencv.org/t/opencv-js-support-for-findhomography/1126)
**Author:** [@Scott\_Suhy](https://forum.opencv.org/u/Scott_Suhy)\ **Replies:** 22\ **Last updated:** [October 22, 2024, 2:56pm UTC](https://forum.opencv.org/t/opencv-js-support-for-findhomography/1126 "2024-10-22T14:56:05Z")
can anyone point me to a working example of calling findHomography() using opencv.js? I believe it is part of the subset. --- ## [OpenCV NodeJS API needed](https://forum.opencv.org/t/opencv-nodejs-api-needed/19024)
**Author:** [@Kevin\_Sun](https://forum.opencv.org/u/Kevin_Sun)\ **Replies:** 2\ **Last updated:** [October 20, 2024, 9:16am UTC](https://forum.opencv.org/t/opencv-nodejs-api-needed/19024 "2024-10-20T09:16:27Z")
OpenCV should definitely provide NodeJS APIs, since a lot popular webapp and desktop app frameworks relies on NodeJS. --- ## [\[OpenCV.js\] Cannot use the TrackerKCF update function](https://forum.opencv.org/t/opencv-js-cannot-use-the-trackerkcf-update-function/18959)
**Author:** [@nguy\_n\_ly](https://forum.opencv.org/u/nguy_n_ly)\ **Replies:** 0\ **Last updated:** [October 14, 2024, 4:07am UTC](https://forum.opencv.org/t/opencv-js-cannot-use-the-trackerkcf-update-function/18959 "2024-10-14T04:07:54Z")
Hi there, I’ve built OpenCV.js from OpenCV and opencv-contrib. I can initialize a tracker using new cv.TrackerKCF, but I’m encountering issues when updating the tracker. It shows an error like in image. Has anyone tried… --- ## [Building Stitcher to OpenCV.js](https://forum.opencv.org/t/building-stitcher-to-opencv-js/18850)
**Author:** [@Leandro\_Goncalves](https://forum.opencv.org/u/Leandro_Goncalves)\ **Replies:** 2\ **Last updated:** [September 30, 2024, 12:14am UTC](https://forum.opencv.org/t/building-stitcher-to-opencv-js/18850 "2024-09-30T00:14:45Z")
What files do I need to change to build Stitcher and the stitching module to OpenCV.js? Is there any guide on editing the opencv\_js.config.py file or other files needed for a custom build like this? --- ## [Having trouble downloading the opencv.js library](https://forum.opencv.org/t/having-trouble-downloading-the-opencv-js-library/18469)
**Author:** [@Dossbromahu](https://forum.opencv.org/u/Dossbromahu)\ **Replies:** 2\ **Last updated:** [August 11, 2024, 11:47am UTC](https://forum.opencv.org/t/having-trouble-downloading-the-opencv-js-library/18469 "2024-08-11T11:47:53Z")
all my greetings to you and all my respects in fact. I would like to ask you for a grievance. I’m having trouble downloading the opencv.js library that works with facial recognition. --- ## [Unable to build ximgproc module from contrib for opencv\_js](https://forum.opencv.org/t/unable-to-build-ximgproc-module-from-contrib-for-opencv-js/18464)
**Author:** [@ceniei](https://forum.opencv.org/u/ceniei)\ **Replies:** 0\ **Last updated:** [August 9, 2024, 1:24pm UTC](https://forum.opencv.org/t/unable-to-build-ximgproc-module-from-contrib-for-opencv-js/18464 "2024-08-09T13:24:49Z")
I am trying to use the procedure at (OpenCV: Build OpenCV.js) to build opencv\_js with the opencv\_contrib modules, but I am not able to do so successfully. I noticed that the imgcodecs module is disabled by default in th… --- ## [OpenCV and ReactNative](https://forum.opencv.org/t/opencv-and-reactnative/251)
**Author:** [@iuri](https://forum.opencv.org/u/iuri)\ **Replies:** 6\ **Last updated:** [December 13, 2020, 2:05pm UTC](https://forum.opencv.org/t/opencv-and-reactnative/251 "2020-12-13T14:05:15Z")
Hello OpenCVees! I’ve been working with openCV in the backend server, using Python, and now I’d like to install openCV as a component in React Native to implement Face’s SignIn/SignUp feature. The goal isn’t to heavily… --- ## [OpenCV.js does not work from a web worker if WASM threads are enabled](https://forum.opencv.org/t/opencv-js-does-not-work-from-a-web-worker-if-wasm-threads-are-enabled/18010)
**Author:** [@andynewman](https://forum.opencv.org/u/andynewman)\ **Replies:** 1\ **Last updated:** [June 20, 2024, 7:53am UTC](https://forum.opencv.org/t/opencv-js-does-not-work-from-a-web-worker-if-wasm-threads-are-enabled/18010 "2024-06-20T07:53:23Z")
OpenCV.js does not work for me when built with WASM threads enabled (--threads option active) and used in a web worker. The problem occurs when using OpenCV.js compiled with emscripten (3.1.57, or latest) $ git clone h… --- ## [OpenCV.js built file not working](https://forum.opencv.org/t/opencv-js-built-file-not-working/14866)
**Author:** [@tarek](https://forum.opencv.org/u/tarek)\ **Replies:** 2\ **Last updated:** [June 17, 2024, 2:36pm UTC](https://forum.opencv.org/t/opencv-js-built-file-not-working/14866 "2024-06-17T14:36:02Z")
Hey, I’ve been brawling this setup process forever and am hoping someone can help. I built opencv.js from source using this command: emcmake python3 opencv/platforms/js/build\_js.py build\_asm --disable\_wasm --emscripten… --- ## [Building WASM Opencv.js: 'cv' is a Promise, not an Object](https://forum.opencv.org/t/building-wasm-opencv-js-cv-is-a-promise-not-an-object/17952)
**Author:** [@andynewman](https://forum.opencv.org/u/andynewman)\ **Replies:** 0\ **Last updated:** [June 15, 2024, 6:19pm UTC](https://forum.opencv.org/t/building-wasm-opencv-js-cv-is-a-promise-not-an-object/17952 "2024-06-15T18:19:07Z")
I am currently successfully using OpenCV.js from a web worker. The procedure I have been using so far is importScripts(“https://docs.opencv.org/4.9.0/opencv.js”). This works just fine. More recently, I built OpenCV.js u… --- ## [Markerless tracking and pose estimation](https://forum.opencv.org/t/markerless-tracking-and-pose-estimation/17930)
**Author:** [@ghjrw4](https://forum.opencv.org/u/ghjrw4)\ **Replies:** 1\ **Last updated:** [June 14, 2024, 4:50am UTC](https://forum.opencv.org/t/markerless-tracking-and-pose-estimation/17930 "2024-06-14T04:50:08Z")
Hello everyone, We’re in the process of developing a web application that displays an MJPEG stream. Our goal is to identify specific objects in the video in real-time and perform pose estimation. Ideally, we’d like it t… --- ## [Build the opencv wasm version, and there is no wasm file after the construction](https://forum.opencv.org/t/build-the-opencv-wasm-version-and-there-is-no-wasm-file-after-the-construction/7791)
**Author:** [@ying\_chang](https://forum.opencv.org/u/ying_chang)\ **Replies:** 1\ **Last updated:** [May 20, 2024, 6:29pm UTC](https://forum.opencv.org/t/build-the-opencv-wasm-version-and-there-is-no-wasm-file-after-the-construction/7791 "2024-05-20T18:29:17Z")
Execute command：python3 ./platforms/js/build\_js.py build\_wasm --build\_wasm build\_wasm/bin directory does not exist opencv.wasm file --- ## [Qr detector Opencv.js Polylines from points](https://forum.opencv.org/t/qr-detector-opencv-js-polylines-from-points/17270)
**Author:** [@Rc1025](https://forum.opencv.org/u/Rc1025)\ **Replies:** 1\ **Last updated:** [April 13, 2024, 7:59pm UTC](https://forum.opencv.org/t/qr-detector-opencv-js-polylines-from-points/17270 "2024-04-13T19:59:06Z")
I’m trying to replicate some code from rust/python-bindings to html with js however the points (cv.Mat) seems to be different than the what is returned in these other bindings. For example: Python import cv2 cap = cv2.… --- ## [Image Classification tutorial openCV js](https://forum.opencv.org/t/image-classification-tutorial-opencv-js/17235)
**Author:** [@Gilbert\_Comeau](https://forum.opencv.org/u/Gilbert_Comeau)\ **Replies:** 1\ **Last updated:** [April 9, 2024, 8:26pm UTC](https://forum.opencv.org/t/image-classification-tutorial-opencv-js/17235 "2024-04-09T20:26:58Z")
I,m going though the image classification tutorial: https://docs.opencv.org/3.4/js\_image\_classification.html#appendix I’m trying to read the net file and config and it’s throwing a numerical error when doing so: try … --- ## [I am encountering an error while attempting to load the 'haarcascade\_eye.xml' file using OpenCV.js. The error message is as follows](https://forum.opencv.org/t/i-am-encountering-an-error-while-attempting-to-load-the-haarcascade-eye-xml-file-using-opencv-js-the-error-message-is-as-follows/14354)
**Author:** [@MTHappen\_Make\_Things](https://forum.opencv.org/u/MTHappen_Make_Things)\ **Replies:** 1\ **Last updated:** [March 21, 2024, 2:56pm UTC](https://forum.opencv.org/t/i-am-encountering-an-error-while-attempting-to-load-the-haarcascade-eye-xml-file-using-opencv-js-the-error-message-is-as-follows/14354 "2024-03-21T14:56:47Z")
I am encountering an error while attempting to load the ‘haarcascade\_eye.xml’ file using OpenCV.js. The error message is as follows A:\[ERROR:0@1.713\] global persistence.cpp:512 open Can’t open file: :‘haarcascade\_front… --- ## [Global persistence.cpp:505 open Can't open file in read mode](https://forum.opencv.org/t/global-persistence-cpp-505-open-cant-open-file-in-read-mode/12581)
**Author:** [@Mihail](https://forum.opencv.org/u/Mihail)\ **Replies:** 20\ **Last updated:** [March 21, 2024, 2:13pm UTC](https://forum.opencv.org/t/global-persistence-cpp-505-open-cant-open-file-in-read-mode/12581 "2024-03-21T14:13:10Z")
\[ERROR:0@3.179\] global persistence.cpp:505 open Can’t open file: ‘haarcascade\_frontalface\_default.xml’ in read mode put\_char @ opencv.js:30 opencv.js:30 \[ERROR:0@3.184\] global persistence.cpp:505 open Can’t open file:… --- ## [Trying to calculate field of view of smartphone camera using rotation sensors](https://forum.opencv.org/t/trying-to-calculate-field-of-view-of-smartphone-camera-using-rotation-sensors/16135)
**Author:** [@moritz](https://forum.opencv.org/u/moritz)\ **Replies:** 4\ **Last updated:** [January 12, 2024, 9:42pm UTC](https://forum.opencv.org/t/trying-to-calculate-field-of-view-of-smartphone-camera-using-rotation-sensors/16135 "2024-01-12T21:42:51Z")
Hey people, I am trying to calculate the field of view of my smartphone camera without taking a calibration photo but instead by rotating the phone taking images on the fly saving the phone orientation for each image … --- ## [Adding custom functions to opencvjs](https://forum.opencv.org/t/adding-custom-functions-to-opencvjs/16013)
**Author:** [@tarek](https://forum.opencv.org/u/tarek)\ **Replies:** 1\ **Last updated:** [December 30, 2023, 6:39pm UTC](https://forum.opencv.org/t/adding-custom-functions-to-opencvjs/16013 "2023-12-30T18:39:41Z")
How would I go about adding my own functions into the opencv source so that they will be usable by whatever includes my built opencv.js? [Next page](https://forum.opencv.org/tag/opencvjs/65.md?match_all_tags=true&page=1&tags%5B%5D=opencvjs)