Make lodepng optional.

README.md

@@ -130,7 +130,7 @@ if (!ret) {
 * `TINYGLTF_NO_STB_IMAGE_WRITE` : Do not write images with stb_image_write. Instead use `TinyGLTF::SetImageWriter(WriteimageDataFunction WriteImageData, void *user_data)` to set a callback for writing images.
 * `TINYGLTF_NO_EXTERNAL_IMAGE` : Do not try to load external image file. This option woulde be helpful if you do not want load image file during glTF parsing.
 * `TINYGLTF_ANDROID_LOAD_FROM_ASSETS`: Load all files from packaged app assets instead of the regular file system. **Note:** You must pass a valid asset manager from your android app to `tinygltf::asset_manager` beforehand.
-* `TINYGLTF_NO_LODEPNG` : Do not load 16bit PNG image with lodepng. Instead use `TinyGLTF::SetImageLoader(LoadimageDataFunction LoadImageData, void *user_data)` to set a callback for loading images(You'll also need to disable stb image with `TINYGLTF_NO_STB_IMAGE`).
+* `TINYGLTF_USE_LODEPNG` : Load 16bit PNG image with lodepng(Valid when `TINYGLTF_NO_STB_IMAGE` was **not** defined). Must defined `LODEPNG_IMPLEMENTATION` in one .cc.
 
 ### Saving gltTF 2.0 model
 * [ ] Buffers.

examples/raytrace/image-impl.cc

@@ -0,0 +1,6 @@
+
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
+#define LODEPNG_IMPLEMENTATION
+#include "lodepng.h"

tiny_gltf.h

@@ -1075,7 +1075,7 @@ class TinyGLTF {
 #include "./stb_image_write.h"
 #endif
 
-#ifndef TINYGLTF_NO_LODEPNG
+#if defined(TINYGLTF_USE_LODEPNG)
 #include "./lodepng.h"
 #endif
 
@@ -1621,7 +1621,7 @@ bool LoadImageData(Image *image, const int image_idx, std::string *err, std::str
   unsigned char *data =
       stbi_load_from_memory(bytes, size, &w, &h, &comp, req_comp);
   if (!data) {
-#if !defined(TINYGLTF_NO_LODEPNG)
+#if defined(TINYGLTF_USE_LODEPNG)
     // try to load as 16bit PNG RGBA
     unsigned ret = lodepng_decode_memory(&data, reinterpret_cast<unsigned *>(&w), reinterpret_cast<unsigned *>(&h), bytes, size, LCT_RGBA, /* bitdepth*/16);