无法使用 stb_image

Question

I was working on a project and I was trying to get an image to load so I could use it as a texture, but I ran into an issue when I tried to include stb_image.

I put stb_image.h in src/vendor/stb_image/ , made a cpp file named stb_image.cpp with

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

in the file, and put the file in the src/vendor/stb_image/ directory. When I try to include #include "vendor/stb_image/stb_image.h" and use it, I get this error:

: && /usr/bin/c++  -Wall -Werror -std=c++14 -g   CMakeFiles/opengl-learning.dir/src/Debug.cpp.o CMakeFiles/opengl-learning.dir/src/IndexBuffer.cpp.o CMakeFiles/opengl-learning.dir/src/Renderer.cpp.o CMakeFiles/opengl-learning.dir/src/Shader.cpp.o CMakeFiles/opengl-learning.dir/src/Texture.cpp.o CMakeFiles/opengl-learning.dir/src/VertexArray.cpp.o CMakeFiles/opengl-learning.dir/src/VertexBuffer.cpp.o CMakeFiles/opengl-learning.dir/src/main.cpp.o  -o opengl-learning  -lglfw /usr/lib64/libGLEW.so /usr/lib/x86_64-linux-gnu/libOpenGL.so /usr/lib/x86_64-linux-gnu/libGLX.so /usr/lib/x86_64-linux-gnu/libGLU.so && :
/usr/bin/ld: CMakeFiles/opengl-learning.dir/src/Texture.cpp.o: in function `Texture::Texture(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
/home/user/Documents/CPP-Stuff/OpenGL-Learning/src/Texture.cpp:5: undefined reference to `stbi_set_flip_vertically_on_load'
/usr/bin/ld: /home/user/Documents/CPP-Stuff/OpenGL-Learning/src/Texture.cpp:6: undefined reference to `stbi_load'
/usr/bin/ld: /home/user/Documents/CPP-Stuff/OpenGL-Learning/src/Texture.cpp:23: undefined reference to `stbi_image_free'
collect2: error: ld returned 1 exit status

This is the code I am trying to run, that makes use of stb_image:

stbi_set_flip_vertically_on_load(1);                                        
m_LocalBuffer = stbi_load(path.c_str(), &m_Width, &m_Height, &m_BPP, 4);  

I've tried putting #define STB_IMAGE_IMPLEMENTATION in the file using stb_image and then including it, but that didn't work very well. It was better than before, but when I tried loading the images, nothing happened. I printed out some of the image data with

stbi_set_flip_vertically_on_load(1);                                        
m_LocalBuffer = stbi_load(path.c_str(), &m_Width, &m_Height, &m_BPP, 4);    
                                                              
std::cout << "m_BPP: " << m_BPP << " m_Width: " << m_Width << " m_Height: " << m_Height << std::endl;

It printed m_BPP: 0 m_Width: 0 m_Height: 0 (the default values, meaning that it didn't load anything). m_LocalBuffer was empty as well. I don't have any opengl errors, or compiler errors, so I have no idea what I'm doing wrong. I'm using cmake and ninja to build, if that's any help. The cmake file and the build.sh file I am using to build will be included below.

CMakeLists:

cmake_minimum_required (VERSION 3.5)

if(POLICY CMP0072)
    cmake_policy(SET CMP0072 NEW)
else(NOT POLICY CMP0072)
    message(STATUS "Error")
endif(POLICY CMP0072)

project (opengl-learning)

find_package(PkgConfig REQUIRED)
pkg_search_module(GLFW REQUIRED glfw3)
include_directories(${GLFW_INCLUDE_DIRS} ${OPENGL_INCLUDE_DIR})

set (GCC_COVERAGE_LINK_FLAGS "-lglfw3 -pthread -ldl -lGLU -lGL -lrt -lXrandr -lXxf86vm -lXi -lXinerama -lX11 -lGLEW -lGLU -lGL")

add_definitions(${GCC_COVERAGE_COMPILE_FLAGS})

set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Werror -std=c++14")
set (source_dir "${PROJECT_SOURCE_DIR}/src/")

file (GLOB source_files "${source_dir}/*.cpp")

add_executable (opengl-learning ${source_files})

find_package(OpenGL REQUIRED)
find_package(GLEW REQUIRED)

target_link_libraries(opengl-learning ${GLFW_LIBRARIES} ${GLEW_LIBRARIES} ${OPENGL_LIBRARIES})

build.sh:

#!/bin/sh

cmake -G "Ninja" -DCMAKE_BUILD_TYPE=Debug
ninja

I can put all of my code on github and send a link to the repo if necessary.

Answer 1

The file which contains the implementation of the stb methods ( src/vendor/stb_image/stb_image.cpp ) is not part of your compilation as can be seen by checking which cpp files are mentioned in your build command.

The reason for this is that the cmake file is set up to only compile files in the src folder, but not files in the src/vendor/stb_image/ folder. You have to add those files in order to get the implementation of the library into your project.