merge and update all copies of stb_image.h

code/AssetLib/M3D/M3DWrapper.h

@@ -56,6 +56,10 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //#define ASSIMP_USE_M3D_READFILECB
 //#define M3D_ASCII
 
+// Share stb_image's PNG loader with other importers/exporters instead of bringing our own copy.
+#define STBI_ONLY_PNG
+#include <contrib/stb_image/stb_image.h>
+
 #include "m3d.h"
 
 namespace Assimp {

code/Common/Assimp.cpp

@@ -1251,3 +1251,36 @@ ASSIMP_API void aiQuaternionInterpolate(
     ai_assert(nullptr != end);
     aiQuaternion::Interpolate(*dst, *start, *end, factor);
 }
+
+
+// stb_image is a lightweight image loader. It is shared by:
+//  - M3D import
+//  - PBRT export
+// Since it's a header-only library, its implementation must be instantiated in some cpp file.
+// Don't scatter this task over multiple importers/exporters. Maintain it in a central place (here!).
+
+#define ASSIMP_HAS_PBRT_EXPORT (!ASSIMP_BUILD_NO_EXPORT && !ASSIMP_BUILD_NO_PBRT_EXPORTER)
+#define ASSIMP_HAS_M3D ((!ASSIMP_BUILD_NO_EXPORT && !ASSIMP_BUILD_NO_M3D_EXPORTER) || !ASSIMP_BUILD_NO_M3D_IMPORTER)
+
+#if ASSIMP_HAS_PBRT_EXPORT
+#   define ASSIMP_NEEDS_STB_IMAGE 1
+#elif ASSIMP_HAS_M3D
+#   define ASSIMP_NEEDS_STB_IMAGE 1
+#   define STBI_ONLY_PNG
+#endif
+
+#if ASSIMP_NEEDS_STB_IMAGE
+
+#   if _MSC_VER // "unreferenced function has been removed" (SSE2 detection routine in x64 builds)
+#       pragma warning(push)
+#       pragma warning(disable: 4505)
+#   endif
+
+#   define STB_IMAGE_IMPLEMENTATION
+#   include "../contrib/stb_image/stb_image.h"
+
+#   if _MSC_VER
+#       pragma warning(pop)
+#   endif
+
+#endif

code/Pbrt/PbrtExporter.cpp

@@ -83,8 +83,7 @@ Other:
 #include <sstream>
 #include <string>
 
-#define STB_IMAGE_IMPLEMENTATION
-#include "stb_image.h"
+#include "../contrib/stb_image/stb_image.h"
 
 using namespace Assimp;