cpiger / qml-cvcamera

QML plugin wrapper for fast OpenCV camera access on desktop & Android

qml-cvcamera

CVCamera is a QML wrapper for fast camera access using OpenCV. It works on desktop and Android.

The following is required for CVCamera to work:

• Ubuntu 14.04
• Qt 5.3.2 (also tested on 5.3.1)
• OpenCV 3.0.0-alpha(master build should also just work)

QML API

The QML API consists of the following:

• device : int - ID of the camera that will be opened, usually goes like 0, 1, ...
• size : QSize - Size of the camera image
• deviceList : QStringList - Names of the detected cameras, indices corresponding to IDs
• cvImage : QVariant - Contains the camera image as a cv::Mat

The full API (API above + non-user parts) can be seen in cvcamera.types.

CVCamera can be used in one or both of two ways:

• Set a CVCamera object as the source property of a VideoOutput in order to display in on the screen
• Set a CVCamera object's cvImage property as some property of a QML object to export the camera image as a cv::Mat. The format of this image is usually RGB in desktop and YUV420sp (a.k.a YUV NV21) on Android.

Desktop Build

1. Install libv4l-dev.

2. Build and install OpenCV:

cd platforms
mkdir build-desktop
cd build-desktop
cmake ../.. -DCMAKE_INSTALL_PREFIX=/usr

At this point, OpenCV components other than calib3d, core, features2d, flann, highgui, imgcodecs, imgproc, video and videoio are not needed and can be disabled. Note: I had to disable WITH_GSTREAMER manually for it to compile without errors. It is not needed and can be disabled. These options can be accessed with ccmake ../...

make -j 5
make install

3. Build and install CVCamera:

mkdir build-desktop
cd build-desktop
/qt/install/root/5.3/gcc_64/bin/qmake ..
make -j 5
make install

Now the CVCamera QML plugin is installed alongside Qt's QML plugins and can be used similar to any other plugin.

Android Build

In addition to the OS, Qt and OpenCV requirements, you need:

• Android SDK and Android API 14 (Android version 4.0)

• Android NDK r9d

These instructions assume armv7-a target architecture. For other architectures, adapt the instructions to your liking.

1. Export a standalone NDK toolchain:

cd /path-to-android-ndk-r9d
./build/tools/make-standalone-toolchain.sh \
    --platform=android-14 \
    --install-dir=/desired/path/to/android/standalone/toolchain \
    --toolchain=arm-linux-androideabi-4.8

Be aware that if you don't have write access to /desired/path/to/android/standalone/toolchain, the script fails silently.

2. Set up the following environment variables:

export ANDROID_HOME=/path/to/android/sdk/linux
export ANDROID_SDK_ROOT=$ANDROID_HOME
export ANDROID_SDK=$ANDROID_SDK_ROOT
export ANDROID_NDK_ROOT=/path-to-android-ndk-r9d
export ANDROID_NDK=$ANDROID_NDK_ROOT
export ANDROID_NDK_STANDALONE_TOOLCHAIN=/path/to/android/standalone/toolchain
export ANDROID_STANDALONE_TOOLCHAIN=$ANDROID_NDK_STANDALONE_TOOLCHAIN
export ANDROID_ABI=armeabi-v7a
export ANDROID_NATIVE_API_LEVEL=14
export ANDROID_TOOLCHAIN_NAME=arm-linux-androideabi-4.8

3. Build and install OpenCV:

cd platforms
mkdir build-android
cd build-android
cmake ../.. \
    -DCMAKE_TOOLCHAIN_FILE=../android/android.toolchain.cmake \
    -DCMAKE_INSTALL_PREFIX=$ANDROID_STANDALONE_TOOLCHAIN/sysroot/usr/share/opencv/

At this point, enable BUILD_SHARED_LIBS.

OpenCV components other than calib3d, core, features2d, flann, highgui, imgcodecs, imgproc, video and videoio are not needed and can be disabled. Leave these options untouched if you are unsure what to do.

The options can be accessed with ccmake ../.. after running cmake.

make -j 5
make install

4. Build and install CVCamera:

mkdir build-android
cd build-android
/qt/install/root/5.3/android_armv7/bin/qmake ..
make -j 5
make install

Now the CVCamera QML plugin is installed alongside Qt's QML plugins and can be used similar to any other plugin.

Note that you still need to bundle the required OpenCV libraries with ANDROID_EXTRA_LIBS and give camera access to your app with ANDROID_PERMISSIONS and ANDROID_FEATURES in the project that uses CVCamera. See samples/preview/preview.pro for an example.

Running Samples

See samples/README.md.