OpenCV on Xcode

Setting up Xcode for OpenCV project

OpenCV is one of the best if not the best computer vision library to use and therefore, many people with various backgrounds get their hands dirty trying it out. Developers using macOS as their primary operating system may use Xcode IDE since it is a key development environment to creating applications for Apple products. If you are interested in using OpenCV in your Xcode project, the following steps might help you.

Install OpenCV on macOS

Because you are a macOS user, you probably already use homebrew for package management. Then the easiest way to install OpenCV libary is

brew install opencv

It will install all dependencies on the fly as well.

Install pkg-config

pkg-config is a very handy tool to ask for package information to use in your projects. To install it, use

brew install pkg-config

Since you want to use OpenCV library in your project and want to know all the flags to pass to compiler, you need to do

pkg-config --cflags --libs opencv4

It will give something like this:

-I/usr/local/Cellar/opencv/4.2.0_1/include/opencv4/opencv -I/usr/local/Cellar/opencv/4.2.0_1/include/opencv4 -L/usr/local/Cellar/opencv/4.2.0_1/lib -lopencv_gapi -lopencv_stitching -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_dnn_objdetect -lopencv_dnn_superres -lopencv_dpm -lopencv_highgui -lopencv_face -lopencv_freetype -lopencv_fuzzy -lopencv_hfs -lopencv_img_hash -lopencv_line_descriptor -lopencv_quality -lopencv_reg -lopencv_rgbd -lopencv_saliency -lopencv_sfm -lopencv_stereo -lopencv_structured_light -lopencv_phase_unwrapping -lopencv_superres -lopencv_optflow -lopencv_surface_matching -lopencv_tracking -lopencv_datasets -lopencv_text -lopencv_dnn -lopencv_plot -lopencv_videostab -lopencv_videoio -lopencv_xfeatures2d -lopencv_shape -lopencv_ml -lopencv_ximgproc -lopencv_video -lopencv_xobjdetect -lopencv_objdetect -lopencv_calib3d -lopencv_imgcodecs -lopencv_features2d -lopencv_flann -lopencv_xphoto -lopencv_photo -lopencv_imgproc -lopencv_core

Xcode Build Settings

Once the OpenCV is successfully installed, create a new Xcode project for macOS as a Command Line Tool and go to the Build Settings. Search with "Search Path" phrase and modify Include Search Path and Library Search Path variables. You need to find where the library is installed. If installed via homebrew, then it is most likely under /usr/local/Cellar/. When modify them, you will see a non-recursive option on the right side of the entry, make it recursive. See example below:

Next is to add linker options. Remember using pkg-config tool? Basically, we will take that entire output and add them to Other Linker Flags variable. Notice that there will be -I/usr/local/Cellar/opencv/4.2.0_1/include/opencv4/opencv -I/usr/local/Cellar/opencv/4.2.0_1/include/opencv4 and -L/usr/local/Cellar/opencv/4.2.0_1/lib in the results. This is potentially what you have done for the Include and Library search path variables but for some reason Xcode does not find <opencv2/core.hpp> if you do not modify these variables. Anyways, search for Other Linker Flags and add the entire results of pkg-config --cflags --libs opencv4 to your linker flags variable.

And that is it.

Xcode OpenCV project Template

I have not been able to create a template for macOS Command Line Tool projects but looks like you can create an Xcode project template for other projects (iOS app, watchOS app, etc.) You can easily find the details on google.

Have fun.