Update README.

Check bit depth when saving image as PNG.

README.md

@@ -7,6 +7,8 @@ If you are looking for old, C++03 version, please use `devel-picojson` branch.
 
 ## Status
 
+v2.2.0 release(Support loading 16bit PNG)
+v2.1.0 release(Draco support)
 v2.0.0 release(22 Aug, 2018)!
 
 ## Builds
@@ -38,14 +40,15 @@ v2.0.0 release(22 Aug, 2018)!
 * Image(Using stb_image)
   * [x] Parse BASE64 encoded embedded image data(DataURI).
   * [x] Load external image file.
-  * [x] PNG(8bit only)
-  * [x] JPEG(8bit only)
-  * [x] BMP
-  * [x] GIF
+  * [x] Load PNG(8bit and 16bit)
+  * [x] Load JPEG(8bit only)
+  * [x] Load BMP
+  * [x] Load GIF
   * [x] Custom Image decoder callback(e.g. for decoding OpenEXR image)
 * Load from memory
 * Custom callback handler
   * [x] Image load
+  * [x] Image save
 * Extensions
   * [x] Draco mesh decoding
 
@@ -69,9 +72,11 @@ v2.0.0 release(22 Aug, 2018)!
 * [ ] Mesh Compression/decompression(Open3DGC, etc)
   * [x] Load Draco compressed mesh
   * [x] Save Draco compressed mesh
+  * [ ] Open3DGC?
 * [ ] Support `extensions` and `extras` property
 * [ ] HDR image?
   * [ ] OpenEXR extension through TinyEXR.
+* [ ] 16bit PNG support in Serialization
 * [ ] Write example and tests for `animation` and `skin`
   * [ ] Skinning
   * [ ] Morph targets

tiny_gltf.h

@@ -26,6 +26,7 @@
 // THE SOFTWARE.
 
 // Version:
+//  - v2.2.0 Add loading 16bit PNG support.
 //  - v2.1.0 Add draco compression.
 //  - v2.0.1 Add comparsion feature(Thanks to @Selmar).
 //  - v2.0.0 glTF 2.0!.
@@ -1772,6 +1773,11 @@ bool WriteImageData(const std::string *basepath, const std::string *filename,
   std::vector<unsigned char> data;
 
   if (ext == "png") {
+    if ((image->bits != 8) || (image->pixel_type != TINYGLTF_COMPONENT_TYPE_UNSIGNED_BYTE)) {
+      // Unsupported pixel format
+      return false;
+    }
+
     if (!stbi_write_png_to_func(WriteToMemory_stbi, &data, image->width,
                                 image->height, image->component,
                                 &image->image[0], 0)) {