Merge pull request #45 from Squareys/custom-image-loaders

Allow custom image loaders

README.md

@@ -101,6 +101,7 @@ if (!ret) {
 ## Compile options
 
 * `TINYGLTF_NOEXCEPTION` : Disable C++ exception in JSON parsing. You can use `-fno-exceptions` or by defining the symbol `JSON_NOEXCEPTION` and `TINYGLTF_NOEXCEPTION`  to fully remove C++ exception codes when compiling TinyGLTF.
+* `TINYGLTF_NO_STB_IMAGE` : Do not load images with stb_image. Instead use `TinyGLTF::SetImageLoader(LoadimageDataFunction LoadImageData, void *user_data)` to set a callback for loading images.
 
 ### Saving gltTF 2.0 model
 

tiny_gltf.h

@@ -450,7 +450,7 @@ struct Image {
   std::vector<unsigned char> image;
   int bufferView;        // (required if no uri)
   std::string mimeType;  // (required if no uri) ["image/jpeg", "image/png", "image/bmp", "image/gif"]
-  std::string uri;       // (reqiored if no mimeType)
+  std::string uri;       // (required if no mimeType)
   Value extras;
 
   Image() { bufferView = -1; }
@@ -725,6 +725,17 @@ enum SectionCheck {
   REQUIRE_ALL = 0x3f
 };
 
+///
+/// LoadImageDataFunction type. Signature for custom image loading callbacks.
+///
+typedef bool (*LoadImageDataFunction)(Image *, std::string *, int, int, const unsigned char *, int, void *);
+
+#ifndef TINYGLTF_NO_STB_IMAGE
+// Declaration of default image loader callback
+static bool LoadImageData(Image *image, std::string *err, int req_width,
+                          int req_height, const unsigned char *bytes,
+                          int size, void*);
+#endif
 
 class TinyGLTF {
  public:
@@ -788,6 +799,11 @@ class TinyGLTF {
       const std::string &
           filename /*, bool embedImages, bool embedBuffers, bool writeBinary*/);
 
+  ///
+  /// Set callback to use for loading image data
+  ///
+  void SetImageLoader(LoadImageDataFunction LoadImageData, void *user_data);
+
  private:
   ///
   /// Loads glTF asset from string(memory).
@@ -801,6 +817,14 @@ class TinyGLTF {
   const unsigned char *bin_data_;
   size_t bin_size_;
   bool is_binary_;
+
+  LoadImageDataFunction LoadImageData =
+#ifndef TINYGLTF_NO_STB_IMAGE
+      &tinygltf::LoadImageData;
+#else
+      nullptr;
+#endif
+  void *load_image_user_data_ = nullptr;
 };
 
 #ifdef __clang__
@@ -847,7 +871,11 @@ class TinyGLTF {
 #endif
 
 #include "./json.hpp"
+
+#ifndef TINYGLTF_NO_STB_IMAGE
 #include "./stb_image.h"
+#endif
+
 #ifdef __clang__
 #pragma clang diagnostic pop
 #endif
@@ -1159,11 +1187,15 @@ static bool LoadExternalFile(std::vector<unsigned char> *out, std::string *err,
   return true;
 }
 
+void TinyGLTF::SetImageLoader(LoadImageDataFunction func, void *user_data) {
+    LoadImageData = func;
+    load_image_user_data_ = user_data;
+}
+
+#ifndef TINYGLTF_NO_STB_IMAGE
 static bool LoadImageData(Image *image, std::string *err, int req_width,
                           int req_height, const unsigned char *bytes,
-                          int size) {
-  //std::cout << "size " << size << std::endl;
-
+                          int size, void*) {
   int w, h, comp;
   // if image cannot be decoded, ignore parsing and keep it by its path
   // don't break in this case
@@ -1217,6 +1249,7 @@ static bool LoadImageData(Image *image, std::string *err, int req_width,
 
   return true;
 }
+#endif
 
 static bool IsDataURI(const std::string &in) {
   std::string header = "data:application/octet-stream;base64,";
@@ -1611,7 +1644,8 @@ static bool ParseAsset(Asset *asset, std::string *err,
 static bool ParseImage(Image *image, std::string *err,
                        const json &o, const std::string &basedir,
                        bool is_binary, const unsigned char *bin_data,
-                       size_t bin_size) {
+                       size_t bin_size, LoadImageDataFunction* LoadImageData = nullptr,
+                       void *user_data = nullptr) {
   // A glTF image must either reference a bufferView or an image uri
   double bufferView = -1;
   bool isEmbedded =
@@ -1703,8 +1737,14 @@ static bool ParseImage(Image *image, std::string *err,
     }
   }
 
-  return LoadImageData(image, err, 0, 0, &img.at(0),
-                       static_cast<int>(img.size()));
+  if (*LoadImageData == nullptr) {
+    if (err) {
+      (*err) += "No LoadImageData callback specified.\n";
+    }
+    return false;
+  }
+  return (*LoadImageData)(image, err, 0, 0, &img.at(0),
+                       static_cast<int>(img.size()), user_data);
 }
 
 static bool ParseTexture(Texture *texture, std::string *err,
@@ -2877,7 +2917,7 @@ bool TinyGLTF::LoadFromString(Model *model, std::string *err, const char *str,
         }
         Image image;
         if (!ParseImage(&image, err, it.value(), base_dir,
-                        is_binary_, bin_data_, bin_size_)) {
+                        is_binary_, bin_data_, bin_size_, &this->LoadImageData, load_image_user_data_)) {
           return false;
         }
 
@@ -2897,9 +2937,15 @@ bool TinyGLTF::LoadFromString(Model *model, std::string *err, const char *str,
               model->bufferViews[size_t(image.bufferView)];
           const Buffer &buffer = model->buffers[size_t(bufferView.buffer)];
 
+          if (*LoadImageData == nullptr) {
+            if (err) {
+              (*err) += "No LoadImageData callback specified.\n";
+            }
+            return false;
+          }
           bool ret = LoadImageData(&image, err, image.width, image.height,
                                    &buffer.data[bufferView.byteOffset],
-                                   static_cast<int>(bufferView.byteLength));
+                                   static_cast<int>(bufferView.byteLength), load_image_user_data_);
           if (!ret) {
             return false;
           }