# Uncategorized **URL:** https://forum.opencv.org/c/uncategorized/1.md [Latest](https://forum.opencv.org/latest.md) · [Categories](https://forum.opencv.org/categories.md) · [Tags](https://forum.opencv.org/tags.md) --- ## [Useful Links (Read First!)](https://forum.opencv.org/t/useful-links-read-first/1842)
**Author:** [@tim](https://forum.opencv.org/u/tim)\ **Replies:** 0\ **Last updated:** [February 26, 2021, 4:17pm UTC](https://forum.opencv.org/t/useful-links-read-first/1842 "2021-02-26T16:17:41Z")
Before asking a question in the forum, check out some of these resources and see if you can find a common answer. Documentation Tutorials Super Helpful Wiki Bugs and Issues Here are some additional useful links. Of… --- ## [Old Askbot Forum Link](https://forum.opencv.org/t/old-askbot-forum-link/69)
**Author:** [@tim](https://forum.opencv.org/u/tim)\ **Replies:** 0\ **Last updated:** [December 3, 2020, 3:28pm UTC](https://forum.opencv.org/t/old-askbot-forum-link/69 "2020-12-03T15:28:00Z")
This forum replaces the Askbot answers section. Please use this forum for any new topics, discussions, or questions. If you need to access answers from the previous forum before posting a new question, you can find that… --- ## [Welcome to OpenCV Forum!](https://forum.opencv.org/t/welcome-to-opencv-forum/7)
**Author:** [@system](https://forum.opencv.org/u/system)\ **Replies:** 33\ **Last updated:** [February 10, 2024, 6:18pm UTC](https://forum.opencv.org/t/welcome-to-opencv-forum/7 "2024-02-10T18:18:47Z")
Welcome to the new and improved OpenCV Forum! We’re excited to finally have a better option for discussion, questions, and answers that can be used from multiple platforms including mobile devices and tablets. OpenCV (O… --- ## [Opencv 5 with onnx qustions](https://forum.opencv.org/t/opencv-5-with-onnx-qustions/24734)
**Author:** [@turner](https://forum.opencv.org/u/turner)\ **Replies:** 0\ **Last updated:** [October 2, 2026, 7:28am UTC](https://forum.opencv.org/t/opencv-5-with-onnx-qustions/24734 "2026-10-02T07:28:07Z")
Hi I have some questions regarding opencv5: Is the module dnn still maintained? I have exported a yolov4-tiny from darknet https://darknetcv.ai/ can I be advised me if this will be supported with opencv5/dnn? I want to… --- ## [How reliable is image matching after compression and resizing?](https://forum.opencv.org/t/how-reliable-is-image-matching-after-compression-and-resizing/24733)
**Author:** [@Copyseeker](https://forum.opencv.org/u/Copyseeker)\ **Replies:** 0\ **Last updated:** [October 1, 2026, 5:41am UTC](https://forum.opencv.org/t/how-reliable-is-image-matching-after-compression-and-resizing/24733 "2026-10-01T05:41:31Z")
How reliable is image matching after compression, resizing, and cropping? I’m looking into image matching for reverse image search, especially when an image has been resized, compressed, screenshotted, or slightly cropp… --- ## [Why is the operation \`S0 \>\> 4\` performed when the \`resize\` function takes \`u8\` input and a scalar for the V-direction? Since \`int32\` would not overflow in the scalar case, why is this operation still necessary?](https://forum.opencv.org/t/why-is-the-operation-s0-4-performed-when-the-resize-function-takes-u8-input-and-a-scalar-for-the-v-direction-since-int32-would-not-overflow-in-the-scalar-case-why-is-this-operation-still-necessary/24714)
**Author:** [@penghuihe](https://forum.opencv.org/u/penghuihe)\ **Replies:** 4\ **Last updated:** [September 25, 2026, 7:57am UTC](https://forum.opencv.org/t/why-is-the-operation-s0-4-performed-when-the-resize-function-takes-u8-input-and-a-scalar-for-the-v-direction-since-int32-would-not-overflow-in-the-scalar-case-why-is-this-operation-still-necessary/24714 "2026-09-25T07:57:54Z")
template\<\> struct VResizeLinear\, VResizeLinearVec\_32s8u\> { typedef uchar value\_type; typedef int buf\_type; typedef short alpha\_type; void operato… --- ## [PSA: CascadeClassifier with a missing file does not raise, it fails later in detectMultiScale](https://forum.opencv.org/t/psa-cascadeclassifier-with-a-missing-file-does-not-raise-it-fails-later-in-detectmultiscale/24719)
**Author:** [@ColinGPT9](https://forum.opencv.org/u/ColinGPT9)\ **Replies:** 1\ **Last updated:** [September 22, 2026, 7:14am UTC](https://forum.opencv.org/t/psa-cascadeclassifier-with-a-missing-file-does-not-raise-it-fails-later-in-detectmultiscale/24719 "2026-09-22T07:14:34Z")
Posting this because it cost me a release and the failure mode points nowhere near the cause. cv2.CascadeClassifier given a path that does not exist does NOT raise. You get back an empty classifier, everything looks f… --- ## [Toolbar Definition](https://forum.opencv.org/t/toolbar-definition/24720)
**Author:** [@danielc](https://forum.opencv.org/u/danielc)\ **Replies:** 0\ **Last updated:** [September 21, 2026, 11:55pm UTC](https://forum.opencv.org/t/toolbar-definition/24720 "2026-09-21T23:55:20Z")
Hello all, I am using Opencv V5 C++ and Qt6 cv::imshow(“Display Window”, image); How do I setup/modify toolbar? or opencv qt toolbar Definition? in source code. Thank you. --- ## [Image preprocessing for OCR on glossy, curved and unevenly illuminated packaging](https://forum.opencv.org/t/image-preprocessing-for-ocr-on-glossy-curved-and-unevenly-illuminated-packaging/24711)
**Author:** [@Suraj\_Singh](https://forum.opencv.org/u/Suraj_Singh)\ **Replies:** 2\ **Last updated:** [September 18, 2026, 1:36pm UTC](https://forum.opencv.org/t/image-preprocessing-for-ocr-on-glossy-curved-and-unevenly-illuminated-packaging/24711 "2026-09-18T13:36:34Z")
I’m trying to preprocess smartphone photographs of consumer-product packaging before sending them to PaddleOCR. The challenging images contain combinations of specular highlights, curved surfaces, perspective distortion… --- ## [Computer Vision Task](https://forum.opencv.org/t/computer-vision-task/24508)
**Author:** [@Vijaya\_Raghava](https://forum.opencv.org/u/Vijaya_Raghava)\ **Replies:** 1\ **Last updated:** [September 18, 2026, 2:29am UTC](https://forum.opencv.org/t/computer-vision-task/24508 "2026-09-18T02:29:16Z")
Currently I’m working on a computer vision project in which object detection module is there. When I’m scanning in a super market shelf, it has to show the product name below. Tell me is that possible? If yes, please sug… --- ## [How are world coordinates and extrinsic parameters defined in camera\_calibration.cpp?](https://forum.opencv.org/t/how-are-world-coordinates-and-extrinsic-parameters-defined-in-camera-calibration-cpp/24712)
**Author:** [@imabata](https://forum.opencv.org/u/imabata)\ **Replies:** 1\ **Last updated:** [September 11, 2026, 5:40am UTC](https://forum.opencv.org/t/how-are-world-coordinates-and-extrinsic-parameters-defined-in-camera-calibration-cpp/24712 "2026-09-11T05:40:42Z")
I am using OpenCV’s camera\_calibration.cpp sample for camera calibration with a CIRCLES\_GRID. I am trying to understand how the world (object) coordinate system and the extrinsic parameters are determined in this sample… --- ## [Question regarding GSoC](https://forum.opencv.org/t/question-regarding-gsoc/24698)
**Author:** [@Gamma.rays](https://forum.opencv.org/u/Gamma.rays)\ **Replies:** 0\ **Last updated:** [September 6, 2026, 5:21am UTC](https://forum.opencv.org/t/question-regarding-gsoc/24698 "2026-09-06T05:21:07Z")
Hello! Does anyone know where Google Summer of Code (GSoC) coordination and discussions for 2027 will take place? I just learned that it doesn’t take place on the main OpenCV community forum. Any help would be appreciate… --- ## [Microscope/Telephoto Camera Calibration](https://forum.opencv.org/t/microscope-telephoto-camera-calibration/24695)
**Author:** [@XYYY\_S](https://forum.opencv.org/u/XYYY_S)\ **Replies:** 4\ **Last updated:** [September 3, 2026, 7:37am UTC](https://forum.opencv.org/t/microscope-telephoto-camera-calibration/24695 "2026-09-03T07:37:57Z")
Some problems we’re encountering right now: even though the RMS is small in microscope calibration, the stability of each calibration is really poor. When calibrating two sets of data consecutively, the resulting focal l… --- ## [Multi-View CCTV Pallet Counting: Resolving Interlocking Layer Occlusion via Calibrated Ground Plane & Homography](https://forum.opencv.org/t/multi-view-cctv-pallet-counting-resolving-interlocking-layer-occlusion-via-calibrated-ground-plane-homography/24694)
**Author:** [@Muawiya\_Shakeel](https://forum.opencv.org/u/Muawiya_Shakeel)\ **Replies:** 0\ **Last updated:** [September 2, 2026, 5:53am UTC](https://forum.opencv.org/t/multi-view-cctv-pallet-counting-resolving-interlocking-layer-occlusion-via-calibrated-ground-plane-homography/24694 "2026-09-02T05:53:41Z")
Hello CV community, I am designing a warehouse pallet counting system using two opposing RTSP cameras (Godown4 and IPC, 1080p, ~15–20° tilt) monitoring an unloading bay. The cargo consists of white shrink-wrapped yarn b… --- ## [Using OpenCV with Embarcadero Delphi 10.3.3 (Object Pascal)](https://forum.opencv.org/t/using-opencv-with-embarcadero-delphi-10-3-3-object-pascal/2485)
**Author:** [@rob-1982](https://forum.opencv.org/u/rob-1982)\ **Replies:** 12\ **Last updated:** [August 22, 2026, 5:37pm UTC](https://forum.opencv.org/t/using-opencv-with-embarcadero-delphi-10-3-3-object-pascal/2485 "2026-08-22T17:37:05Z")
Hello to all forum members, I’m new to the forum and also a newbie to OpenCV. As a development system I almost exclusively use Embarcadero Delphi 10.3.3 (sometimes C++ Builder). So far I have already successfully integr… --- ## [Get a Point Cloud from only one Image](https://forum.opencv.org/t/get-a-point-cloud-from-only-one-image/24687)
**Author:** [@Xiangxing\_Xu](https://forum.opencv.org/u/Xiangxing_Xu)\ **Replies:** 0\ **Last updated:** [August 17, 2026, 6:29am UTC](https://forum.opencv.org/t/get-a-point-cloud-from-only-one-image/24687 "2026-08-17T06:29:14Z")
Single Camera + Cross-Line Laser: Dense 3D Point Cloud from One Image Hello everyone, I would like to share an experimental 3D reconstruction project and ask for technical feedback from people working in computer vision… --- ## [Looking to contribute to OpenCV — GSoC 2027 aspirant](https://forum.opencv.org/t/looking-to-contribute-to-opencv-gsoc-2027-aspirant/24670)
**Author:** [@sk\_inthiyaz](https://forum.opencv.org/u/sk_inthiyaz)\ **Replies:** 1\ **Last updated:** [August 7, 2026, 12:45pm UTC](https://forum.opencv.org/t/looking-to-contribute-to-opencv-gsoc-2027-aspirant/24670 "2026-08-07T12:45:43Z")
Hi, I’m Inthiyaz, a 4th-year CSE (AI/ML) student. I’m interested in contributing to OpenCV ahead of GSoC 2027 — looking for good-first-issue recommendations to get started. --- ## [Eye To Hand Calibration Using LeRobot](https://forum.opencv.org/t/eye-to-hand-calibration-using-lerobot/24195)
**Author:** [@Sergio\_Orozco](https://forum.opencv.org/u/Sergio_Orozco)\ **Replies:** 2\ **Last updated:** [July 15, 2026, 10:16pm UTC](https://forum.opencv.org/t/eye-to-hand-calibration-using-lerobot/24195 "2026-07-15T22:16:38Z")
Hello! I am trying to do Eye-to-Hand calibration using a LeRobot SO-101 and stationary Realsense camera. Here is a google drive link which links all the appropriate and necessary information. Link: Opencv Post - Google … --- ## [EU AI Act compliance](https://forum.opencv.org/t/eu-ai-act-compliance/24607)
**Author:** [@Namrata\_Raina](https://forum.opencv.org/u/Namrata_Raina)\ **Replies:** 2\ **Last updated:** [July 10, 2026, 4:49am UTC](https://forum.opencv.org/t/eu-ai-act-compliance/24607 "2026-07-10T04:49:46Z")
@philnelson Does OpenCV 4.5.3 and OpenCV 4.13.0 comply with the EU AI Act? --- ## [Training data / provenance of the res10 SSD face detector](https://forum.opencv.org/t/training-data-provenance-of-the-res10-ssd-face-detector/24612)
**Author:** [@ritesh\_kumar](https://forum.opencv.org/u/ritesh_kumar)\ **Replies:** 0\ **Last updated:** [July 10, 2026, 3:58am UTC](https://forum.opencv.org/t/training-data-provenance-of-the-res10-ssd-face-detector/24612 "2026-07-10T03:58:14Z")
Hi all, We use OpenCV 4.5.3 (DNN module) with the bundled ResNet-10 SSD face detector — res10\_300x300\_ssd\_iter\_140000\_fp16.caffemodel + deploy.prototxt from samples/dnn/face\_detector. We run it for inference only (no tr… --- ## [Homography-based master/slave PTZ camera sync — is this the right approach?](https://forum.opencv.org/t/homography-based-master-slave-ptz-camera-sync-is-this-the-right-approach/24605)
**Author:** [@Gustavo\_Quevedo](https://forum.opencv.org/u/Gustavo_Quevedo)\ **Replies:** 1\ **Last updated:** [July 2, 2026, 7:30pm UTC](https://forum.opencv.org/t/homography-based-master-slave-ptz-camera-sync-is-this-the-right-approach/24605 "2026-07-02T19:30:35Z")
I’ve been experimenting with syncing two PTZ cameras and I’d love some guidance from people who’ve done this for real. The setup: two PTZ cameras pointed at a sports field. One I move around manually (call it the “maste… --- ## [Build OpenCV 5 with CMake failed](https://forum.opencv.org/t/build-opencv-5-with-cmake-failed/24592)
**Author:** [@Simon1](https://forum.opencv.org/u/Simon1)\ **Replies:** 3\ **Last updated:** [July 1, 2026, 6:59am UTC](https://forum.opencv.org/t/build-opencv-5-with-cmake-failed/24592 "2026-07-01T06:59:12Z")
I build opencv 5 with following command but failed cmake -G “Visual Studio 18 2026” -A x64 -S C:/Github/opencv-5.0.0 -B C:/Github/opencv-5-build -D CMAKE\_BUILD\_TYPE=RELEASE -D BUILD\_CUDA\_STUBS=ON -D BUILD\_JAVA=OFF … --- ## [Wide-baseline stereo on circles grid, enormous stereo RMS](https://forum.opencv.org/t/wide-baseline-stereo-on-circles-grid-enormous-stereo-rms/24595)
**Author:** [@marisano](https://forum.opencv.org/u/marisano)\ **Replies:** 11\ **Last updated:** [June 26, 2026, 11:48am UTC](https://forum.opencv.org/t/wide-baseline-stereo-on-circles-grid-enormous-stereo-rms/24595 "2026-06-26T11:48:29Z")
Thanks so much for providing this test code! I’ve used it as the basis of my own asymmetric circle grid stereo calibration code. Intrinsic camera parameter determination functions well (0.3 and 0.5 rms error), but when I… --- ## [Microsoft made std::mutex constexpr in the STL for VS17.10 and later](https://forum.opencv.org/t/microsoft-made-std-mutex-constexpr-in-the-stl-for-vs17-10-and-later/24597)
**Author:** [@Pragmataraxia](https://forum.opencv.org/u/Pragmataraxia)\ **Replies:** 1\ **Last updated:** [June 24, 2026, 11:29am UTC](https://forum.opencv.org/t/microsoft-made-std-mutex-constexpr-in-the-stl-for-vs17-10-and-later/24597 "2026-06-24T11:29:30Z")
If you try to build OpenCV 4 or 5 Release with Visual Studio 17.10 or later with dynamic C runtime, it will die on the first attempt to use a mutex (which will be during trace initialization, or logging initialization if… --- ## [Calculation of pipe dimensions, pipe geometry](https://forum.opencv.org/t/calculation-of-pipe-dimensions-pipe-geometry/24585)
**Author:** [@GANDA1F7](https://forum.opencv.org/u/GANDA1F7)\ **Replies:** 1\ **Last updated:** [June 17, 2026, 10:30pm UTC](https://forum.opencv.org/t/calculation-of-pipe-dimensions-pipe-geometry/24585 "2026-06-17T22:30:01Z")
We are using YOLO11 segmentation to detect inner and outer contours of a pipe cross-section. The goal is to measure inner diameter, outer diameter and wall thickness in millimeters. The challenge is that segmentation mas… --- ## [ArUco detection on macOS (AVFoundation → OpenCV 4) intermittently returns no markers — sanity check on params/pipeline?](https://forum.opencv.org/t/aruco-detection-on-macos-avfoundation-opencv-4-intermittently-returns-no-markers-sanity-check-on-params-pipeline/24590)
**Author:** [@jmachler](https://forum.opencv.org/u/jmachler)\ **Replies:** 4\ **Last updated:** [June 17, 2026, 3:19pm UTC](https://forum.opencv.org/t/aruco-detection-on-macos-avfoundation-opencv-4-intermittently-returns-no-markers-sanity-check-on-params-pipeline/24590 "2026-06-17T15:19:43Z")
ArUco detection on macOS (AVFoundation → OpenCV 4) intermittently returns no markers — sanity check on params/pipeline? Hi all — I’m running an ArUco detector on macOS using AVFoundation for capture and OpenCV 4 (Homebr… --- ## [Matchtemplate SQDIFF has minValue != 0 for identical image/template](https://forum.opencv.org/t/matchtemplate-sqdiff-has-minvalue-0-for-identical-image-template/24518)
**Author:** [@kinram](https://forum.opencv.org/u/kinram)\ **Replies:** 4\ **Last updated:** [May 29, 2026, 4:14pm UTC](https://forum.opencv.org/t/matchtemplate-sqdiff-has-minvalue-0-for-identical-image-template/24518 "2026-05-29T16:14:04Z")
Based on the SQDIFF formula: OpenCV: Object Detection I expected to get a minValue of 0 when the template and the image are identical, because the square difference is 0 for each pixel in each channel, so the sum must b… --- ## [Stereo Calibration: Very high radial distortion coefficients](https://forum.opencv.org/t/stereo-calibration-very-high-radial-distortion-coefficients/24517)
**Author:** [@rrahman1215](https://forum.opencv.org/u/rrahman1215)\ **Replies:** 3\ **Last updated:** [May 26, 2026, 9:19pm UTC](https://forum.opencv.org/t/stereo-calibration-very-high-radial-distortion-coefficients/24517 "2026-05-26T21:19:12Z")
I am getting very high radial distortion coefficients after calibration which is unusual for the type of lense I’m using. When I try to reconstruct speckled squares/rectangles I get ~10% compression in X (horizontal) dir… --- ## [Why doesn't OpenCV officially compile the OpenVINO version anymore?](https://forum.opencv.org/t/why-doesnt-opencv-officially-compile-the-openvino-version-anymore/24516)
**Author:** [@ZJD](https://forum.opencv.org/u/ZJD)\ **Replies:** 0\ **Last updated:** [May 25, 2026, 7:15am UTC](https://forum.opencv.org/t/why-doesnt-opencv-officially-compile-the-openvino-version-anymore/24516 "2026-05-25T07:15:12Z")
A little doubt,Why doesn’t OpenCV officially compile the OpenVINO version anymore? --- ## [How to distinguish exterior wall outline lines from hatch, dimension, and view-crop lines in architectural elevation PDFs?](https://forum.opencv.org/t/how-to-distinguish-exterior-wall-outline-lines-from-hatch-dimension-and-view-crop-lines-in-architectural-elevation-pdfs/24496)
**Author:** [@mta](https://forum.opencv.org/u/mta)\ **Replies:** 4\ **Last updated:** [May 11, 2026, 4:37pm UTC](https://forum.opencv.org/t/how-to-distinguish-exterior-wall-outline-lines-from-hatch-dimension-and-view-crop-lines-in-architectural-elevation-pdfs/24496 "2026-05-11T16:37:28Z")
Hi everyone, I’m building a construction plan takeoff pipeline for architectural drawings. I’m using Python and OpenCV to analyze architectural elevation PDFs that may be rasterized or converted to images. The specific… [Next page](https://forum.opencv.org/c/uncategorized/1.md?page=1)