DepthAI C++ Library

Core C++ library

Documentation

Documentation is available over at Luxonis DepthAI API

Disclaimer

DepthAI library doesn't yet provide API stability guarantees. While we take care to properly deprecate old functions, some changes might still be breaking. We expect to provide API stability from version 3.0.0 onwards.

Dependencies

• CMake >= 3.10
• C/C++14 compiler
• [optional] OpenCV 4 (required if building examples)

MacOS: Optional brew install opencv

Linux: Optional sudo apt install libopencv-dev

Building

Make sure submodules are updated

git submodule update --init --recursive

Then configure and build

cmake -S. -Bbuild
cmake --build build

ℹ️ To speed up build times, use cmake --build build --parallel [num CPU cores] (CMake >= 3.12). For older versions use: Linux/macOS: cmake --build build -- -j[num CPU cores], MSVC: cmake --build build -- /MP[num CPU cores]

⚠️ If any CMake commands error with CMake Error: The source directory "" does not exist. replace argument -S with -H

Dynamic library

To build dynamic version of library configure with following option added

cmake -S. -Bbuild -D'BUILD_SHARED_LIBS=ON'
cmake --build build

Android

Android is supported to some extent but not actively pursued nor tested. PRs with any improvements are welcome.

Steps:

• Install Android NDK (for example via Android Studio).
• Set the NDK path:

export ANDROID_HOME=$HOME/.local/lib/Android
export PATH=$PATH:$ANDROID_HOME/emulator:$ANDROID_HOME/platform-tools
export NDK=$ANDROID_HOME/ndk/23.1.7779620/ # Check version

• Ensure a recent version of cmake (apt version is outdated, install snap install cmake --classic)
• Run cmake, set your ABI and Platform as needed:

cmake -S. -Bbuild -DCMAKE_TOOLCHAIN_FILE=$NDK/build/cmake/android.toolchain.cmake -DANDROID_ABI=armeabi-v7a -DANDROID_PLATFORM=android-25
cmake --build build

Running examples

To build the examples configure with following option added

cmake -S. -Bbuild -D'DEPTHAI_BUILD_EXAMPLES=ON'
cmake --build build

Then navigate to build/examples folder and run a preferred example

cd build/examples
./MobileNet/rgb_mobilenet

ℹ️ Multi-Config generators (like Visual Studio on Windows) will have the examples built in build/examples/MobileNet/[Debug/Release/...]/rgb_mobilenet

Integration

Under releases you may find prebuilt library for Windows, for use in either integration method. See Releases

CMake

Targets available to link to are:

• depthai::core - Core library, without using opencv internally
• depthai::opencv - Core + support for opencv related helper functions (requires OpenCV4)

Using find_package

Build static or dynamic version of library (See: Building and optionally Installing)

Add find_package and target_link_libraries to your project

find_package(depthai CONFIG REQUIRED)
...
target_link_libraries([my-app] PRIVATE depthai::opencv)

And point CMake to either build directory or install directory:

-D'depthai_DIR=depthai-core/build'

or

-D'depthai_DIR=depthai-core/build/install/lib/cmake/depthai'

If library was installed to default search path like /usr/local on Linux, specifying depthai_DIR isn't necessary as CMake will find it automatically.

Using add_subdirectory

This method is more intrusive but simpler as it doesn't require building the library separately.

Add add_subdirectory which points to depthai-core folder before project command. Then link to any required targets.

add_subdirectory(${CMAKE_CURRENT_LIST_DIR}/depthai-core EXCLUDE_FROM_ALL)
...
project(my-app)
...
target_link_libraries([my-app] PRIVATE depthai::opencv)

Non-CMake integration (Visual Studio, Xcode, CodeBlocks, ...)

To integrate into a different build system than CMake, prefered way is compiling as dynamic library and setting correct build options.

1. First build as dynamic library: Building Dynamic library
2. Then install: Installing

In your non-CMake project (new Visual Studio project, ...)

1. Set needed library directories:
   • build/install/lib (for linking to either depthai-core or depthai-opencv)
   • build/install/bin (for .dll's)
2. And include directories
   • build/install/include (library headers)
   • build/install/include/depthai-shared/3rdparty (shared 3rdparty headers)
   • build/install/lib/cmake/depthai/dependencies/include (dependency headers)

ℹ️ Threading library might need to be linked to explicitly.

ℹ️ Check build/depthai-core-integration.txt or build/depthai-opencv-integration.txt for up to date define options. The generated integration file also specifies include paths without requiring installation.

Installing

To install specify optional prefix and build target install

cmake -S. -Bbuild -D'CMAKE_INSTALL_PREFIX=[path/to/install/dir]'
cmake --build build --target install

If CMAKE_INSTALL_PREFIX isn't specified, the library is installed under build folder install.

Environment variables

The following environment variables can be set to alter default behavior of the library without having to recompile

Running tests

To run the tests build the library with the following options

cmake -S. -Bbuild -D'DEPTHAI_TEST_EXAMPLES=ON' -D'DEPTHAI_BUILD_TESTS=ON' -D'DEPTHAI_BUILD_EXAMPLES=ON'
cmake --build build

Then navigate to build folder and run ctest with specified labels that denote device type to test on. Currently available labels:

• usb
• poe

cd build
# Run tests on USB devices
ctest -L usb
# Run tests on PoE devices
ctest -L poe

Style check

The library uses clang format to enforce a certain coding style. If a style check is failing, run the clangformat target, check the output and push changes.

To use this target clang format must be installed, preferably clang-format-10

sudo apt install clang-format-10

And to apply formatting

cmake --build build --target clangformat

Documentation generation

Doxygen is used to generate documentation. Follow doxygen download and install the required binaries for your platform.

After that specify CMake define -D'DEPTHAI_BUILD_DOCS=ON' and build the target doxygen

Debugging tips

Debugging can be done using Visual Studio Code and either GDB or LLDB (extension 'CodeLLDB'). LLDB in some cases was much faster to step with and resolved more incomplete_type variables than GDB. Your mileage may vary though.

If there is a need to step into Hunter libraries, that can be achieved by removing previous built artifacts

rm -r ~/.hunter

And configuring the project with the following CMake option set to ON

cmake . -D'HUNTER_KEEP_PACKAGE_SOURCES=ON'

This retains the libraries source code, so that debugger can step through it (the paths are already set up correctly)

Troubleshooting

Build fails with missing OpenCV dependency

If your build process happen to fail due to OpenCV library not being found, but you have the OpenCV installed, please run build with additional -D'OpenCV_DIR=...' flag (replacing default Ubuntu path /usr/lib/x86_64-linux-gnu/cmake/opencv4 with yours)

cmake -S. -Bbuild -D'OpenCV_DIR=/usr/lib/x86_64-linux-gnu/cmake/opencv4'

Now the build process should correctly discover your OpenCV installation

Hunter

Hunter is a CMake-only dependency manager for C/C++ projects.

If you are stuck with error message which mentions external libraries (subdirectory of .hunter) like the following:

/usr/bin/ld: /home/[user]/.hunter/_Base/062a19a/ccfed35/a84a713/Install/lib/liblzma.a(stream_flags_decoder.c.o): warning: relocation against `lzma_footer_magic' in read-only section `.text'

Try erasing the Hunter cache folder.

Linux/MacOS:

rm -r ~/.hunter

Windows:

del C:/.hunter

or

del C:/[user]/.hunter