Makefile to Compile OpenCV Code in C++ on Ubuntu/Linux

Question

I am learning OpenCV using Learning OpenCV book.

One problem I am facing while compiling the code is that I have to write a long command to compile and get the executabl

Answer 1

You can create a file called Makefile in you working directory like this:

CFLAGS = `pkg-config --cflags opencv`
LIBS = `pkg-config --libs opencv`

% : %.cpp
        g++ $(CFLAGS) $(LIBS) -o $@ $<

then you can use this file for all your single-file programms. Just call make with the basename of the file you want to compile. For facedetect.cpp that would be

make facedetect

Here some more details:

The general format of a makefile is like this:

target : dependecy1 dependenc2 ...
    command that generates the target

So for your example you could write:

facedetect : facedetect.cpp
    g++  $(CFLAGS) $(LIBS) -o facedetect facedetect.cpp

For each new example you can now create a new target. But you can also make it more general:

% : %.cpp
    g++  $(CFLAGS) $(LIBS) -o $@ $<

Here % matches any nonempty substring. The automatic variables $@ and $< substitute the names of the target file and the source file. For more information you can consult the make documentation.

Answer 2

GNU Make is pretty smart and the Makefile you need for this doesn't need to be as verbose as in the other answers given so far. Here is a simple Makefile which you can use to compile the OpenCV examples:

CPPFLAGS = $(shell pkg-config --cflags opencv)
LDLIBS = $(shell pkg-config --libs opencv)

That's it. The Makefile can be this short thanks to Make's implicit rules.

Then run make as usual:

make facedetect

This assumes there is a facedetect.c or facedetect.cpp in the same directory.

I recommend the following (free!) book if you want to learn Make: http://oreilly.com/catalog/make3/book/index.csp

Answer 3

Create a file named makefile in your working directory that contains the following:

CFLAGS = $SHELL(pkg-config --cflags opencv)
LIBS = $SHELL(pkg-config --libs opencv)

facedetect : facedetect.cpp
    g++ $(CFLAGS) $(LIBS) -o $@ $<

Then when you want to compile you just type:

$ make

(To answer your PS - note that CMake is very different from make - for now you should probaby just use make.)