kandi X-RAY | OpenCV-android Summary
kandi X-RAY | OpenCV-android Summary
【开发中】OpenCV Android 实现人脸识别、图片处理、图片相似度检测、物体识别功能。（基于OpenCV Library v3.2.0）
Top functions reviewed by kandi - BETA
- Delivers the camera frame
- Measure the frame
- Initialize the ticker
- Converts an image into Android bitmap
- Sets the camera preview size
- Initialize camera preview
- Calculate the size of the acc preview
- Sets this matrix to the given values
- Completes state
- Opens camera
- Calculate the values of a camera matrix
- Called when the view is loaded
- Rectify 3 matrices
- Convert a vector to a Matcher
- Convert a vector vector to a matrix
- Initializes OpenCV libs
- Creates a hash code
- Compares two matrices
- Decomposes homography matrices
- Calculates the hash code
- Set the camera preview size
- Register a new package
- Create cascade classifier
- Opens a camera
- Initializes the view
- Convert a vector to a Matrix
OpenCV-android Key Features
OpenCV-android Examples and Code Snippets
Trending Discussions on OpenCV-android
I was trying to build and execute a cpp code that links few opencv shared libraries that I had cross compiled for android but while trying to utilize the namespace cv or trying to use a function of opencv, it says undeclared identifier. I did try this documentation here: https://developer.android.com/ndk/guides/prebuilts but was unable to get it working. Also I referred to another stackoverflow question for reference here: OpenCV with Android NDK Undefined References as well. Any guidance on how to link them and import opencv functions properly which I am probably missing out here would be really helpful.
ANSWERAnswered 2022-Feb-17 at 12:30
I've fixed the issue myself, it was a linking issue along with modifying the Android.mk file accordingly. For others who may encounter the issue: My Android.Mk file after the fix looks like
I am integrating existing C++ code that uses OpenCV to an Android app, using Android studio. For this purpose, I have installed the package
OpenCV-android-sdk and added it as a module to Android studio. I have also created a simple Kotlin app.
So far I have managed to integrate my C++ code into the project. After adding the paths to the OpenCV includes by means of an
include_directories statement, the code compiles successfully.
My next step would be to link against the precompiled OpenCV library, to resolve the "undefined symbol" errors. I have no idea how to achieve this/where to specify it. I have tried to find resources on the web, but not two resources tell the same and the solutions seem overly complicated. I am lost in the jungle....
ANSWERAnswered 2022-Jan-04 at 11:08
I finally managed. Here comes the recipe (validated under Windows).
Make sure to download the
OpenCV Android SDK and copy it somewhere.
The project must be created as a
Native C++ app (Phone and tablet). A
cpp folder is automatically created with a
native-lib.cpp source file and a
Add the following lines to the
CMakeLists file, after the
I tried to compile a .so library using Visual Studio 2019 along with OpenCV Android in order to use this library in Unity. There are some answers on how to configure Visual Studio to use OpenCV Android (here or here) but none of these work for me. Below you can see my configurations.
Visual Studio 2019 (running on Windows 10)
android-ndk-r21e // also tried with android-ndk-r15c android-ndk-r16b and android-ndk-r17c
OpenCV Android 4.5.2 // also tried with OpenCV Android 4.0.0, 4.0.1 and 4.1.0
My settings in Visual Studio 2019 look as follows:
Platform Toolset Clang 5.0 (also tried Clang 3.8 or GCC 4.9)
Configuration Type Dynamic Library (.so)
Target API Level Nougat 7.0 (android-24) (also tried different versions)
Use STL LLVM libc++ static library (c++_static) (also tried "GNU STL static library (gnustl_static)")
Additional Include Directories "Path to OpenCV_4_5_2_Android\sdk\native\jni\include"
Code Generation Enable C++ Exceptions "Yes(-fexceptions)"
Precompiled Headers Not using Precompiled Headers
- Additional Library Directories Path to OpenCV_4_5_2_Android\sdk\native\libs\armeabi-v7a
- Additional Dependencies Path to OpenCV_4_5_2_Android\sdk\native\libs\armeabi-v7a\libopencv_java4.so
My Source.cpp I try to compile is just a single function for testing purposes...
ANSWERAnswered 2021-Jun-10 at 16:27
I had the exact same issue as you (though I used c++ 11) with the exact same setup, and struggled for days. I believe the errors you're seeing (like me) are from arm_neon.h. Very oddly, I was able to just build (not run) the .so successfully, even with those errors (I say "errors" because if you look at arm_neon.h, others pop up), so try it. Maybe it's some kind of IntelliJ/Intellisense mistake more than anything else where it's catching false negatives from some other toolchain setup.
At the same time, I'm not 100% sure I was always able to build with that issue, so try these steps as well if you can't:
- use OpenCV 4.0.1 with Android NDK 16rb. The NDK matters when it comes to OpenCV builds, and this is the only supposed match that I know of.
- follow this tutorial from scratch: https://amin-ahmadi.com/2019/06/03/how-to-use-opencv-in-unity-for-android/
- if the downloaded OpenCV android SDK is still giving trouble, build OpenCV from the source using his other tutorial here: https://amin-ahmadi.com/2019/02/03/how-to-build-opencv-4-x-for-native-android-development/ and then repeat step 2.
MAJOR EDIT: OpenCV 4.5.2 needs to be treated differently because it no longer uses toolchains with gnu c++. -When you build OpenCV from CMake, build with Android NDK 21e, and do not use the toolchain in OpenCV 4.5.2. Use the one inside the Android NDK's build folder (android-ndk-r21e\build\cmake). -When you build your .so from Visual Studio 2019, do not use the GNU STL, use the LLVM. GNU c++ is no longer part of Android NDKs, and you need to cut it out of the process entirely. -In the Linker Input, put the names of your library files (or file, if it's just the world one) in the Library Dependencies field, not the Additional Dependencies field. -Everything else is the same as in those common tutorials.
I'm trying to setup OpenCv 3.4.14 on Android Studio (4.0.0) project which has c++ support from the beginning, (Native project). I'm getting this error over and over again. I searched the web and didn't found any useful solution for that problem, please help.
I followed this video for setting up OpenCv on Android Studio. It works well in the video, but for some reason it doesn't work for me.
I've tried to setup OpenCv on projects that don't include c++, and it worked without any problem. What makes me think that the problem here is somewhere in the CMakeLists.txt file.
So i will share here all what i have (after following the video above):
ANSWERAnswered 2021-Apr-20 at 23:27
To anyone who struggle configuring OpenCV in a native c++ Android projects, I've found this video useful, it is the best guide for setting up OpenCV on Android. All the work is done only by the CMake file. It worked for me.
I am working with CMakeList.txt file and need to set a path to my lib. Currently I do it this way:...
ANSWERAnswered 2020-Nov-01 at 11:50
What am I doing wrong?
You are reading cmake variable and expecting it to expand to the value of the environment variable.
how to convert env var value from key to actual value.
I had used openCV for android from this repo https://github.com/quickbirdstudios/opencv-android. its worked and also camera was running. But there is a issue with camera orientation in this repo. So I just forked and published mine using https://jitpack.io/ without any changes (just to check if its working).
ANSWERAnswered 2020-Sep-26 at 13:07
Good morning everyone. I am currently working on a project in which I have to detect object coordinates within an image with high precision. I have tried using a normal chessboard for camera calibration but the reprojection error was too high so I decided to use the Charuco calibration pattern. I am working with OpenCv 3.4 and Java (project constraint). Since the Aruco function are not included in OpenCv for Java I created a new package in my project which includes the necessary classes. The Aruco code is the one that you can find in the following link : Aruco Code Github
The code that I'm executing is the following:...
ANSWERAnswered 2020-Jul-23 at 15:07
The error indicates that you have opencv package without special module you're using;
In order to fix that you'd need to either find a prebuilt opencv with module you need (in your exactly case it's lcoated in contrib library, so this probably helps.
In case you want to build it from sources - you should enable the module you want in cmake properties. For contrib - you'd need to cmake contrib project first & then enable contrib in main opencv makefile. For building opencv & contirb - please follow official documentation.
ANSWERAnswered 2020-Jul-16 at 13:50
In HSV color space, Hue represents the traditional colors which we perceive. Another main difference is that when RGB color space represented as a cube, HSV is a cylinder so the range of Hue is actually
0 to 360 degrees. Hue represents Green values between
~121 to ~180 degrees and when we rescale that to the input range of Opencv functions (0-255) the value of green should be between
85 to 128. If you are looking for a visual representation this page has a nice interactive model for both RGB and HSV color spaces.
I have been trying to do this from past few days. Aim is to access android camera and stream frames on the screen using opencv library....
ANSWERAnswered 2020-May-07 at 23:14
I just have followed this with the latest(like you) version of everything. And it's working! Enjoy!
I am giving my version of instructions thinking about if the link ever gets broken.
- Download opencv sdk for android at: https://opencv.org/releases.html
Unzip opencv sdk and place it in the same root of sample project folder
No vulnerabilities reported
You can use OpenCV-android like any standard Java library. Please include the the jar files in your classpath. You can also use any IDE and you can run and debug the OpenCV-android component as you would do with any other Java program. Best practice is to use a build tool that supports dependency management such as Maven or Gradle. For Maven installation, please refer maven.apache.org. For Gradle installation, please refer gradle.org .
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