Convert custom VAEs during legacy checkpoint loading (#3010)

- When a legacy checkpoint model is loaded via --convert_ckpt and its
models.yaml stanza refers to a custom VAE path (using the 'vae:' key),
the custom VAE will be converted and used within the diffusers model.
Otherwise the VAE contained within the legacy model will be used.
    
- Note that the checkpoint import functions in the CLI or Web UIs
continue to default to the standard stabilityai/sd-vae-ft-mse VAE. This
can be fixed after the fact by editing VAE key using either the CLI or
Web UI.
   
- Fixes issue #2917

invokeai/backend/model_management/convert_ckpt_to_diffusers.py

@@ -1036,6 +1036,15 @@ def convert_open_clip_checkpoint(checkpoint):
 
     return text_model
 
+def replace_checkpoint_vae(checkpoint, vae_path:str):
+    if vae_path.endswith(".safetensors"):
+        vae_ckpt = load_file(vae_path)
+    else:
+        vae_ckpt = torch.load(vae_path, map_location="cpu")
+    state_dict = vae_ckpt['state_dict'] if "state_dict" in vae_ckpt else vae_ckpt
+    for vae_key in state_dict:
+        new_key = f'first_stage_model.{vae_key}'
+        checkpoint[new_key] = state_dict[vae_key]
 
 def load_pipeline_from_original_stable_diffusion_ckpt(
     checkpoint_path: str,
@@ -1048,6 +1057,7 @@ def load_pipeline_from_original_stable_diffusion_ckpt(
     extract_ema: bool = True,
     upcast_attn: bool = False,
     vae: AutoencoderKL = None,
+    vae_path: str = None,
     precision: torch.dtype = torch.float32,
     return_generator_pipeline: bool = False,
     scan_needed:bool=True,
@@ -1078,6 +1088,8 @@ def load_pipeline_from_original_stable_diffusion_ckpt(
     :param precision: precision to use - torch.float16, torch.float32 or torch.autocast
     :param upcast_attention: Whether the attention computation should always be upcasted. This is necessary when
     running stable diffusion 2.1.
+    :param vae: A diffusers VAE to load into the pipeline.
+    :param vae_path: Path to a checkpoint VAE that will be converted into diffusers and loaded into the pipeline.
     """
 
     with warnings.catch_warnings():
@@ -1214,9 +1226,19 @@ def load_pipeline_from_original_stable_diffusion_ckpt(
 
         unet.load_state_dict(converted_unet_checkpoint)
 
-        # Convert the VAE model, or use the one passed
-        if not vae:
-            print("   | Using checkpoint model's original VAE")
+        # If a replacement VAE path was specified, we'll incorporate that into
+        # the checkpoint model and then convert it
+        if vae_path:
+            print(f"  | Converting VAE {vae_path}")
+            replace_checkpoint_vae(checkpoint,vae_path)
+        # otherwise we use the original VAE, provided that
+        # an externally loaded diffusers VAE was not passed
+        elif not vae:
+            print("  | Using checkpoint model's original VAE")
+
+        if vae:
+            print("  | Using replacement diffusers VAE")
+        else:  # convert the original or replacement VAE
             vae_config = create_vae_diffusers_config(
                 original_config, image_size=image_size
             )
@@ -1226,8 +1248,6 @@ def load_pipeline_from_original_stable_diffusion_ckpt(
 
             vae = AutoencoderKL(**vae_config)
             vae.load_state_dict(converted_vae_checkpoint)
-        else:
-            print("   | Using external VAE specified in config")
 
         # Convert the text model.
         model_type = pipeline_type

invokeai/backend/model_management/model_manager.py

@@ -45,9 +45,6 @@ class SDLegacyType(Enum):
     UNKNOWN = 99
 
 DEFAULT_MAX_MODELS = 2
-VAE_TO_REPO_ID = {  # hack, see note in convert_and_import()
-    "vae-ft-mse-840000-ema-pruned": "stabilityai/sd-vae-ft-mse",
-}
 
 class ModelManager(object):
     '''
@@ -457,15 +454,21 @@ class ModelManager(object):
 
         from . import load_pipeline_from_original_stable_diffusion_ckpt
 
-        self.offload_model(self.current_model)
-        if vae_config := self._choose_diffusers_vae(model_name):
-            vae = self._load_vae(vae_config)
+        try:
+            if self.list_models()[self.current_model]['status'] == 'active':
+                self.offload_model(self.current_model)
+        except Exception as e:
+            pass
+        
+        vae_path = None
+        if vae:
+            vae_path = vae if os.path.isabs(vae) else os.path.normpath(os.path.join(Globals.root, vae))
         if self._has_cuda():
             torch.cuda.empty_cache()
         pipeline = load_pipeline_from_original_stable_diffusion_ckpt(
             checkpoint_path=weights,
             original_config_file=config,
-            vae=vae,
+            vae_path=vae_path,
             return_generator_pipeline=True,
             precision=torch.float16 if self.precision == "float16" else torch.float32,
         )
@@ -512,6 +515,7 @@ class ModelManager(object):
         print(f">> Offloading {model_name} to CPU")
         model = self.models[model_name]["model"]
         model.offload_all()
+        self.current_model = None
 
         gc.collect()
         if self._has_cuda():
@@ -795,15 +799,16 @@ class ModelManager(object):
         return model_name
 
     def convert_and_import(
-        self,
-        ckpt_path: Path,
-        diffusers_path: Path,
-        model_name=None,
-        model_description=None,
-        vae=None,
-        original_config_file: Path = None,
-        commit_to_conf: Path = None,
-        scan_needed: bool=True,
+            self,
+            ckpt_path: Path,
+            diffusers_path: Path,
+            model_name=None,
+            model_description=None,
+            vae:dict=None,
+            vae_path:Path=None,
+            original_config_file: Path = None,
+            commit_to_conf: Path = None,
+            scan_needed: bool=True,
     ) -> str:
         """
         Convert a legacy ckpt weights file to diffuser model and import
@@ -831,13 +836,17 @@ class ModelManager(object):
         try:
             # By passing the specified VAE to the conversion function, the autoencoder
             # will be built into the model rather than tacked on afterward via the config file
-            vae_model = self._load_vae(vae) if vae else None
+            vae_model=None
+            if vae:
+                vae_model=self._load_vae(vae)
+                vae_path=None
             convert_ckpt_to_diffusers(
                 ckpt_path,
                 diffusers_path,
                 extract_ema=True,
                 original_config_file=original_config_file,
                 vae=vae_model,
+                vae_path=vae_path,
                 scan_needed=scan_needed,
             )
             print(
@@ -884,36 +893,6 @@ class ModelManager(object):
 
         return search_folder, found_models
 
-    def _choose_diffusers_vae(
-        self, model_name: str, vae: str = None
-    ) -> Union[dict, str]:
-        # In the event that the original entry is using a custom ckpt VAE, we try to
-        # map that VAE onto a diffuser VAE using a hard-coded dictionary.
-        # I would prefer to do this differently: We load the ckpt model into memory, swap the
-        # VAE in memory, and then pass that to convert_ckpt_to_diffuser() so that the swapped
-        # VAE is built into the model. However, when I tried this I got obscure key errors.
-        if vae:
-            return vae
-        if model_name in self.config and (
-            vae_ckpt_path := self.model_info(model_name).get("vae", None)
-        ):
-            vae_basename = Path(vae_ckpt_path).stem
-            diffusers_vae = None
-            if diffusers_vae := VAE_TO_REPO_ID.get(vae_basename, None):
-                print(
-                    f">> {vae_basename} VAE corresponds to known {diffusers_vae} diffusers version"
-                )
-                vae = {"repo_id": diffusers_vae}
-            else:
-                print(
-                    f'** Custom VAE "{vae_basename}" found, but corresponding diffusers model unknown'
-                )
-                print(
-                    '** Using "stabilityai/sd-vae-ft-mse"; If this isn\'t right, please edit the model config'
-                )
-                vae = {"repo_id": "stabilityai/sd-vae-ft-mse"}
-        return vae
-
     def _make_cache_room(self) -> None:
         num_loaded_models = len(self.models)
         if num_loaded_models >= self.max_loaded_models:

invokeai/frontend/CLI/CLI.py

@@ -772,16 +772,10 @@ def convert_model(model_name_or_path: Union[Path, str], gen, opt, completer):
             original_config_file = Path(model_info["config"])
             model_name = model_name_or_path
             model_description = model_info["description"]
-            vae = model_info["vae"]
+            vae_path = model_info.get("vae")
         else:
             print(f"** {model_name_or_path} is not a legacy .ckpt weights file")
             return
-        if vae_repo := invokeai.backend.model_management.model_manager.VAE_TO_REPO_ID.get(
-            Path(vae).stem
-        ):
-            vae_repo = dict(repo_id=vae_repo)
-        else:
-            vae_repo = None
         model_name = manager.convert_and_import(
             ckpt_path,
             diffusers_path=Path(
@@ -790,7 +784,7 @@ def convert_model(model_name_or_path: Union[Path, str], gen, opt, completer):
             model_name=model_name,
             model_description=model_description,
             original_config_file=original_config_file,
-            vae=vae_repo,
+            vae_path=vae_path,
         )
     else:
         try: