diff --git a/addons/io_scene_gltf2/__init__.py b/addons/io_scene_gltf2/__init__.py
index ad4969d2c..17a778cd2 100644
--- a/addons/io_scene_gltf2/__init__.py
+++ b/addons/io_scene_gltf2/__init__.py
@@ -113,18 +113,18 @@ def __init__(self):
 
     export_image_format = EnumProperty(
         name='Images',
-        items=(('NAME', 'Automatic',
-                'Determine the image format from the blender image name'),
+        items=(('AUTO', 'Automatic',
+                'Save PNGs as PNGs and JPEGs as JPEGs.\n'
+                'If neither one, use PNG'),
                 ('JPEG', 'JPEG Format (.jpg)',
-                'Encode and save textures as .jpg files. Be aware of a possible loss in quality'),
-               ('PNG', 'PNG Format (.png)',
-                'Encode and save textures as .png files')
+                'Save images as JPEGs. (Images that need alpha are saved as PNGs though.)\n'
+                'Be aware of a possible loss in quality'),
                ),
         description=(
             'Output format for images. PNG is lossless and generally preferred, but JPEG might be preferable for web '
             'applications due to the smaller file size'
         ),
-        default='NAME'
+        default='AUTO'
     )
 
     export_texture_dir = StringProperty(
diff --git a/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py b/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py
index 0f83a4c48..e99d71b13 100644
--- a/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py
+++ b/addons/io_scene_gltf2/blender/exp/gltf2_blender_gather_image.py
@@ -42,7 +42,7 @@ def gather_image(
         # The export image has no data
         return None
 
-    mime_type = __gather_mime_type(blender_shader_sockets_or_texture_slots, export_settings)
+    mime_type = __gather_mime_type(blender_shader_sockets_or_texture_slots, image_data, export_settings)
     name = __gather_name(blender_shader_sockets_or_texture_slots, export_settings)
 
     uri = __gather_uri(image_data, mime_type, name, export_settings)
@@ -95,27 +95,20 @@ def __gather_extras(sockets_or_slots, export_settings):
     return None
 
 
-def __gather_mime_type(sockets_or_slots, export_settings):
+def __gather_mime_type(sockets_or_slots, export_image, export_settings):
     # force png if Alpha contained so we can export alpha
     for socket in sockets_or_slots:
         if socket.name == "Alpha":
             return "image/png"
 
-    if export_settings["gltf_image_format"] == "NAME":
-        extension = __get_extension_from_slot(sockets_or_slots, export_settings)
-        extension = extension.lower()
-        if extension in [".jpeg", ".jpg", ".png"]:
-            return {
-                ".jpeg": "image/jpeg",
-                ".jpg": "image/jpeg",
-                ".png": "image/png",
-            }[extension]
+    if export_settings["gltf_image_format"] == "AUTO":
+        image = export_image.blender_image()
+        if image is not None and image.file_format == 'JPEG':
+            return "image/jpeg"
         return "image/png"
 
     elif export_settings["gltf_image_format"] == "JPEG":
         return "image/jpeg"
-    else:
-        return "image/png"
 
 
 def __gather_name(sockets_or_slots, export_settings):
@@ -245,23 +238,3 @@ def __get_texname_from_slot(sockets_or_slots, export_settings):
 
     elif isinstance(sockets_or_slots[0], bpy.types.MaterialTextureSlot):
         return sockets_or_slots[0].texture.image.name
-
-
-@cached
-def __get_extension_from_slot(sockets_or_slots, export_settings):
-    if __is_socket(sockets_or_slots):
-        for socket in sockets_or_slots:
-            node = __get_tex_from_socket(socket, export_settings)
-            if node is not None:
-                image_name = node.shader_node.image.name
-                filepath = bpy.data.images[image_name].filepath
-                name, extension = os.path.splitext(filepath)
-                if extension:
-                    return extension
-        return '.png'
-
-    elif isinstance(sockets_or_slots[0], bpy.types.MaterialTextureSlot):
-        image_name = sockets_or_slots[0].texture.image.name
-        filepath = bpy.data.images[image_name].filepath
-        name, extension = os.path.splitext(filepath)
-        return extension
diff --git a/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py b/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py
index 0a9fbc428..4011d6b09 100644
--- a/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py
+++ b/addons/io_scene_gltf2/blender/exp/gltf2_blender_image.py
@@ -86,15 +86,18 @@ def is_filled(self, chan: Channel) -> bool:
     def empty(self) -> bool:
         return not self.fills
 
+    def blender_image(self) -> Optional[bpy.types.Image]:
+        """If there's an existing Blender image we can use,
+        returns it. Otherwise (if channels need packing),
+        returns None.
+        """
+        if self.__on_happy_path():
+            for fill in self.fills.values():
+                return fill.image
+        return None
+
     def __on_happy_path(self) -> bool:
-        # Whether there is an existing Blender image we can use for this
-        # ExportImage because all the channels come from the matching
-        # channel of that image, eg.
-        #
-        #     self.fills = {
-        #         Channel.R: FillImage(image=im, src_chan=Channel.R),
-        #         Channel.G: FillImage(image=im, src_chan=Channel.G),
-        #     }
+        # All src_chans match their dst_chan and come from the same image
         return (
             all(isinstance(fill, FillImage) for fill in self.fills.values()) and
             all(dst_chan == fill.src_chan for dst_chan, fill in self.fills.items()) and
@@ -115,8 +118,7 @@ def encode(self, mime_type: Optional[str]) -> bytes:
         return self.__encode_unhappy()
 
     def __encode_happy(self) -> bytes:
-        for fill in self.fills.values():
-            return self.__encode_from_image(fill.image)
+        return self.__encode_from_image(self.blender_image())
 
     def __encode_unhappy(self) -> bytes:
         result = self.__encode_unhappy_with_compositor()