mingw cannot find png.h for libpng on Windows

I am working on a project that requires me to use CImg which in turn needs libpng. I am using CLion and cmake with MinGW-W64 GCC-8.1.0. I have been following this answer - https://stackoverflow.com/a/41956016/11382155 to get it set up.

This is how my CMakeLists.txt looks

cmake_minimum_required(VERSION 3.15)
project(CImgProject)

set(CMAKE_CXX_STANDARD 14)

set(SOURCE_FILES main.cpp)
add_executable(CImgProject ${SOURCE_FILES})

# You can alter these according to your needs, e.g if you don't need to display images - set(YOU_NEED_X11 0)
set(YOU_NEED_X11 1)
set(YOU_NEED_PNG 1)

if(${YOU_NEED_X11} EQUAL 1)
    message(STATUS "Looking for X11...")
    find_package(X11 REQUIRED)
    include_directories(${X11_INCLUDE_DIR})
    target_link_libraries(CImgProject ${X11_LIBRARIES})
else()
    target_compile_definitions(CImgProject PRIVATE cimg_display=0)
endif()

if(${YOU_NEED_PNG} EQUAL 1)
    message(STATUS "Looking for libpng...")
    set(ZLIB_ROOT "CImg283/zlib-1.2.11")
    set(ZLIB_LIBRARY "CImg283/zlib-1.2.11")
    set(PNG_ROOT "CImg283/lpng1637")
    set(PNG_LIBRARY "CImg283/lpng1637")
    find_package(PNG REQUIRED)
    include_directories(${PNG_INCLUDE_DIR})
    target_link_libraries (CImgProject ${PNG_LIBRARY})
    target_compile_definitions(CImgProject PRIVATE cimg_use_png=1)
endif()

This is my main.cpp

#include "CImg283/CImg.h"

using namespace cimg_library;

int main() {
    CImg<unsigned char> img(640,400,1,3);         // Define a 640x400 color image with 8 bits per color component.
    img.fill(0);                                  // Set pixel values to 0 (color : black)
    unsigned char purple[] = { 255,0,255 };       // Define a purple color
    img.draw_text(100,100,"Hello World",purple);  // Draw a purple "Hello world" at coordinates (100,100).
    img.display("Window Title");                  // Display the image in a display window.
    img.save_png("test.png");                     // Save as PNG to prove we linked correctly
    return 0;
}

The problem I have is that when I hit build, I get the following error

====================[ Build | CImgProject | Debug ]=============================
"C:\Program Files\JetBrains\CLion 2019.1\bin\cmake\win\bin\cmake.exe" --build C:\Users\bhave\OneDrive\Desktop\untitled\cmake-build-debug --target CImgProject -- -j 6
Scanning dependencies of target CImgProject
[ 50%] Building CXX object CMakeFiles/CImgProject.dir/main.cpp.obj
In file included from C:\Users\bhave\OneDrive\Desktop\untitled\main.cpp:3:
C:\Users\bhave\OneDrive\Desktop\untitled\CImg283/CImg.h:447:10: fatal error: png.h: No such file or directory
 #include "png.h"
          ^~~~~~~
compilation terminated.
mingw32-make.exe[3]: *** [CMakeFiles\CImgProject.dir\build.make:63: CMakeFiles/CImgProject.dir/main.cpp.obj] Error 1
mingw32-make.exe[2]: *** [CMakeFiles\Makefile2:75: CMakeFiles/CImgProject.dir/all] Error 2
mingw32-make.exe[1]: *** [CMakeFiles\Makefile2:82: CMakeFiles/CImgProject.dir/rule] Error 2
mingw32-make.exe: *** [Makefile:117: CImgProject] Error 2

I don't know why this error is popping up when cmake is able to find libpng and I checked that png.h definitely exists.

I resolved the problem by getting rid of

set(ZLIB_ROOT "CImg283/zlib-1.2.11")
set(ZLIB_LIBRARY "CImg283/zlib-1.2.11")
set(PNG_ROOT "CImg283/lpng1637")
set(PNG_LIBRARY "CImg283/lpng1637")

and just grabbing the mingw-64 library distribution from https://packages.msys2.org/package/mingw-w64-x86_64-libpng and putting the files in the correct location inside my mingw distribution. Be sure to put it in both mingw folders inside the 64 bit installation.