macOS+homebrew : C++でopencv4

ビルドできなくてえらい苦労したのでメモ

導入

brew install opencv

> brew info opencv
opencv: stable 4.0.1 (bottled)
Open source computer vision library
https://opencv.org/
/usr/local/Cellar/opencv/4.0.1 (679 files, 226MB) *
  Poured from bottle on 2019-03-07 at 12:11:25
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/opencv.rb
==> Dependencies
Build: cmake ✔, pkg-config ✔
Required: eigen ✔, ffmpeg ✔, jpeg ✔, libpng ✔, libtiff ✔, numpy ✔, openexr ✔, python ✔, python@2 ✔, tbb ✔
==> Analytics
install: 13,231 (30 days), 53,429 (90 days), 231,530 (365 days)
install_on_request: 12,353 (30 days), 48,865 (90 days), 212,007 (365 days)
build_error: 0 (30 days)

ソース

sample1.cc

#include <opencv2/opencv.hpp>

int main(int argc, char* argv[])
{
  //cv::Mat image = cv::Mat::zeros(100, 100, CV_8UC3);
  cv::Mat image = cv::imread("sample.jpg");
  cv::imshow("sample1", image);
  cv::waitKey(0);
  return 0;
}

ビルドオプションに -std=c++11を付けること。

CXX=g++
CXXFLAGS= -Wall -std=c++11 `pkg-config opencv4 --cflags`
OPENCV_LIBS= `pkg-config opencv4 --libs`

all: sample1

sample1: sample1.o
    $(CXX) -g -o $@ $^ $(OPENCV_LIBS)

clean:
    rm -f sample1 *.o *~

.PHONY: all clean

cmakeで書くならこう

CMakeLists.txt

cmake_minimum_required(VERSION 3.10)
find_package(PkgConfig)

project(SampleProject)

pkg_check_modules(OPENCV4 REQUIRED opencv4)

#
# sample1
#

add_executable(sample1
  sample1.cc)

target_include_directories(sample1
  PUBLIC
  ${OPENCV4_INCLUDE_DIRS})

target_link_libraries(sample1
  PUBLIC
  ${OPENCV4_LDFLAGS}
)

target_compile_features(sample1
  PUBLIC
  cxx_std_11)

target_compile_options(sample1
  PUBLIC
  -Wall
  )