glTF exporter: less naive file format detection for textures

1 files changed, 11 insertions, 2 deletions

diff --git a/io_scene_gltf2/blender/exp/gltf2_blender_image.py b/io_scene_gltf2/blender/exp/gltf2_blender_image.py
index 145e1ed9..e9db7e66 100644
--- a/io_scene_gltf2/blender/exp/gltf2_blender_image.py
+++ b/io_scene_gltf2/blender/exp/gltf2_blender_image.py
@@ -272,15 +272,24 @@ class ExportImage:
 
     def __encode_from_image(self, image: bpy.types.Image) -> bytes:
         # See if there is an existing file we can use.
+        data = None
         if image.source == 'FILE' and image.file_format == self.file_format and \
                 not image.is_dirty:
             if image.packed_file is not None:
-                return image.packed_file.data
+                data = image.packed_file.data
             else:
                 src_path = bpy.path.abspath(image.filepath_raw)
                 if os.path.isfile(src_path):
                     with open(src_path, 'rb') as f:
-                        return f.read()
+                        data = f.read()
+        # Check magic number is right
+        if data:
+            if self.file_format == 'PNG':
+                if data.startswith(b'\x89PNG'):
+                    return data
+            elif self.file_format == 'JPEG':
+                if data.startswith(b'\xff\xd8\xff'):
+                    return data
 
         # Copy to a temp image and save.
         tmp_image = None