Stbi loading errors

Question

When I try to use stbi to load an image all I get is this error:

1>Renderer.obj : error LNK2005: "void __cdecl stbi__unpremultiply_on_load_thread(int)" (?stbi__unpremultiply_on_load_thread@@YAXH@Z) already defined in LoadFile.obj

1>Main.obj : error LNK2005: "void __cdecl stbi__unpremultiply_on_load_thread(int)" (?stbi__unpremultiply_on_load_thread@@YAXH@Z) already defined in LoadFile.obj

1>Shape.obj : error LNK2005: "void __cdecl stbi__unpremultiply_on_load_thread(int)" (?stbi__unpremultiply_on_load_thread@@YAXH@Z) already defined in LoadFile.obj

1>Texture.obj : error LNK2005: "void __cdecl stbi__unpremultiply_on_load_thread(int)" (?stbi__unpremultiply_on_load_thread@@YAXH@Z) already defined in LoadFile.obj

and I get about 180 of these errors for different functions.

I include the stbi in one header file and I use this define

#define STB_IMAGE_IMPLEMENTATION
#include <stb_image.h>

Answer 1

If you have multiple .cpp files that use the functions of stb_image.h, including main.cpp, put #define STB_IMAGE_IMPLEMENTATION in main.cpp before the header file that includes stb_image.h.

The structure will look like this:

header1.h

#pragma once
#include "some_header_file.h"
#include "stb_image.h"

void someFunction ();

source1.cpp

#include "header1.h"

void someFunction ()
{
    ...
    // code line which uses functions in stb_image.h, e.g.
    unsigned char* IMGpixels = stbi_load(imgFile, &IMGwidth, &IMGheight, &IMGchannels, 4);
}

main.cpp

#define STB_IMAGE_IMPLEMENTATION // should define this before include stb_image.h, 
#include "header1.h"

int main(int argc, char** argv)
{
    ...
    // code line which uses functions in stb_image.h, e.g.
    unsigned char* data = stbi_load(texFilename, &texWidth, &texHeight, &colorChannels, 0);
}