Compiling OpenCV code on a 64-bit mac

Question

I recently inherited some OpenCV code. I installed openCV on my mac, built in in XCode, and then compiled and successfully ran my first openCV "hello world"-ish program.

Now I'm trying to run the code I was given, but I get errors that lead me to believe it's an issue with the original code being run on a 32-bit Windows system and mine being on a 64-bit Mac.

When I run the Makefile by entering "make"

CC = g++
CFLAGS =
LDFLAGS = -I/usr/local/include/opencv -lm -lopencv_core -lopencv_highgui -lopencv_video
ALL = vision

all: $(ALL)

vision: vision.o
    $(CC) $(LDFLAGS) -o $@ $^

vision.o: vision.cpp
    $(CC) $(LDFLAGS) -c $<

.PHONY: clean

clean:
    rm -rf *.o core* $(ALL)

I get the following output…

g++ -I/usr/local/include/opencv -lm -lopencv_core -lopencv_highgui -lopencv_video -o vision vision.o
Undefined symbols for architecture x86_64:
  "cv::equalizeHist(cv::Mat const&, cv::Mat&)", referenced from:
      _main in vision.o
  "cv::threshold(cv::Mat const&, cv::Mat&, double, double, int)", referenced from:
      _main in vision.o

ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
make: *** [vision] Error 1

I'm confused; does this mean my install of OpenCV is wrong, the code (those methods specifically) needs to be changed, or something else entirely?

Note: When I comment out the problem methods from the vision.cpp code, everything compiles just fine.

Answer 1

Add opencv_imgprocto your LDFLAGS:

LDFLAGS = -I/usr/local/include/opencv -lm -lopencv_core -lopencv_highgui -lopencv_video -lopencv_imgproc

Answer 2

Here is a working example:

CXX = g++

SOURCES = aaa.cpp bbb.cpp
OBJS = $(SOURCES:.cpp=.o)

CXXFLAGS = -I. -I/opt/local/include \
            -std=c++11 -stdlib=libc++ \
            -g3 -Wall -O0
            # -std=c++0x -arch x86_64 -stdlib=libc++ \

LDFLAGS = -L/opt/local/lib -L/usr/lib $(pkg-config --libs --cflags opencv) -lm -ljpeg
LDFLAGS = -L/opt/local/lib -L/usr/lib -I/opt/local/include/opencv -I/opt/local/include -L/opt/local/lib -lopencv_calib3d -lopencv_contrib -lopencv_core -lopencv_features2d -lopencv_flann -lopencv_gpu -lopencv_highgui -lopencv_imgproc -lopencv_legacy -lopencv_ml -lopencv_nonfree -lopencv_objdetect -lopencv_photo -lopencv_stitching -lopencv_superres -lopencv_ts -lopencv_video -lopencv_videostab -lm -ljpeg

.o:
    $(CXX) $(CXXFLAGS) -o $@ -c $^

all: $(OBJS)
    $(CXX) $(CXXFLAGS) $(LDFLAGS) -o out $(OBJS)

clean:
    rm -rf *.o

Answer 3

You can also have the computer guess you the libraries automatically:

CFLAGS = `pkg-config --cflags opencv` 
LDFLAGS = `pkg-config --libs opencv` -lm