How to add ImageMagick/Magick++ to my c++ project with CMake?

Question

I am new to CMake. I was trying to use ImageMagick's c++ api Magick++ in my code.

This is my whole directory structure:

external/image_magick just contains the result of cloning the image magick library using: git submodule add https://github.com/ImageMagick/ImageMagick.git external/image_magick.

This is the top-level CMakeLists.txt ( the one in the pic above):

cmake_minimum_required (VERSION 3.22.1) project(DEMO) add_executable(${PROJECT_NAME} main.cpp)

This is main.cpp (it just crops the image magick image and saves it, just for the demo):

#include <iostream> #include <Magick++.h> using namespace std; using namespace Magick; int main() { cout << "Hello World!" << endl; // Construct the image object. Seperating image construction from the // the read operation ensures that a failure to read the image file // doesn't render the image object useless. Image image; try { // Read a file into image object image.read("logo:"); // Crop the image to specified size (width, height, xOffset, yOffset) image.crop(Geometry(100, 100, 100, 100)); // Write the image to a file image.write("logo.png"); printf("Image written to logo.png"); } catch (Exception &error_) { cout << "Caught exception: " << error_.what() << endl; printf("Error: %s", error_.what()); return 1; } return 0; }

If I compile and run the app like this (as per image magick docs):

c++ main.cpp -o main.out `Magick++-config --cppflags --cxxflags --ldflags --libs` ./main.out

Then all is good and image is generated.

But I can't use the CMakeLists.txt to build and run like this:

cmake -S . -B out/build cd out/build; make cd out/build ./DEMO

Because the external/image_magick directory I cloned does not contain CMakeLists.txt. I tried searching inside that directory for the library file (something like libmagic++??) to use it like below in my top level CMakeLists.txt but I didn't know how to do it:

add_subdirectory(external/image_magick/Magick++) target_include_directories(${PROJECT_NAME} PUBLIC external/image_magick/ ) target_link_directories(${PROJECT_NAME} PRIVATE external/image_magick/Magick++ ) target_link_libraries(${PROJECT_NAME} PUBLIC ${PROJECT_SOURCE_DIR}/Magick++ ) # DOES NOT WORK

So how to properly add this library to my app while keeping using CMAke?

So you have cloned ImageMagick sources. They do not contain the library, you need to build them first. CMake provides module ExternalProject for building external projects during the building of your one. There are many questions on Stack Overflow about using External Project functionality in CMake. See e.g. that one: stackoverflow.com/questions/6351609/… — Tsyvarev
– Tsyvarev, Commented Sep 23, 2022 at 15:21

Maimas2 · Accepted Answer · 2022-09-23 16:46:11Z

0

I have had a similar problem, and it was solved by instead of using link_libraries, using the set command like this:

set(CMAKE_CXX_FLAGS "-LlibraryPath -lMagick++ ${CMAKE_CXX_FLAGS}")

I understand this is not the intended use for this, but this was the way I got my project building.

Also, expect many problems with libraries with C/C++, as everyone has many, many, MANY questions that need asking.

edited Sep 23, 2022 at 16:46

answered Sep 23, 2022 at 15:36

Maimas2

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4 Comments

Tsyvarev Over a year ago

Setting -l options in CMAKE_CXX_FLAGS will never work with gcc, which is sensitive to the order of libraries in the command line. Resulting command line for the linker will firstly has all options from CMAKE_CXX_FLAGS variable and only then all object files. So when the linker will process those object files the libraries from -l options will already be forgotten.

Haidar Over a year ago

didn't work, I am still getting the same error: fatal error: Magick++.h: No such file or directory 3 | #include <Magick++.h> | ^~~~~~~~~~~~ compilation terminated. So do you suggest to use something else instead?

Maimas2 Over a year ago

Sorry, I misunderstood the question, my bad. You should include the ImageMagick++ include directory using the include_directories command. You can learn more here: cmake.org/cmake/help/latest/command/include_directories.html

Haidar Over a year ago

@cs1349459 I already tried this,but here is the problem, if you look at the ImageMagick library repo at github, you can see they don't have an include directory ,they have an Include.h file inside the Magick++ folder, but no include/ directory.

Haidar · Accepted Answer · 2022-10-07 21:43:03Z

According to this answer, the solution was to add the following to CMakeLists.txt:

#ImageMagick add_definitions( -DMAGICKCORE_QUANTUM_DEPTH=16 ) add_definitions( -DMAGICKCORE_HDRI_ENABLE=0 ) find_package(ImageMagick COMPONENTS Magick++) include_directories(${ImageMagick_INCLUDE_DIRS}) target_link_libraries(demo ${ImageMagick_LIBRARIES})

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