Modular backend - T2I Adapter (#6662)

## Summary

T2I Adapter code from #6577.

## Related Issues / Discussions

#6606 

https://invokeai.notion.site/Modular-Stable-Diffusion-Backend-Design-Document-e8952daab5d5472faecdc4a72d377b0d

## QA Instructions

Run with and without set `USE_MODULAR_DENOISE` environment.

## Merge Plan

Nope.
If you think that there should be some kind of tests - feel free to add.

## Checklist

- [x] _The PR has a short but descriptive title, suitable for a
changelog_
- [ ] _Tests added / updated (if applicable)_
- [ ] _Documentation added / updated (if applicable)_

invokeai/app/invocations/denoise_latents.py

@@ -63,6 +63,7 @@
 from invokeai.backend.stable_diffusion.extensions.preview import PreviewExt
 from invokeai.backend.stable_diffusion.extensions.rescale_cfg import RescaleCFGExt
 from invokeai.backend.stable_diffusion.extensions.seamless import SeamlessExt
+from invokeai.backend.stable_diffusion.extensions.t2i_adapter import T2IAdapterExt
 from invokeai.backend.stable_diffusion.extensions_manager import ExtensionsManager
 from invokeai.backend.stable_diffusion.schedulers import SCHEDULER_MAP
 from invokeai.backend.stable_diffusion.schedulers.schedulers import SCHEDULER_NAME_VALUES
@@ -499,6 +500,33 @@ def parse_controlnet_field(
                 )
             )
 
+    @staticmethod
+    def parse_t2i_adapter_field(
+        exit_stack: ExitStack,
+        context: InvocationContext,
+        t2i_adapters: Optional[Union[T2IAdapterField, list[T2IAdapterField]]],
+        ext_manager: ExtensionsManager,
+    ) -> None:
+        if t2i_adapters is None:
+            return
+
+        # Handle the possibility that t2i_adapters could be a list or a single T2IAdapterField.
+        if isinstance(t2i_adapters, T2IAdapterField):
+            t2i_adapters = [t2i_adapters]
+
+        for t2i_adapter_field in t2i_adapters:
+            ext_manager.add_extension(
+                T2IAdapterExt(
+                    node_context=context,
+                    model_id=t2i_adapter_field.t2i_adapter_model,
+                    image=context.images.get_pil(t2i_adapter_field.image.image_name),
+                    weight=t2i_adapter_field.weight,
+                    begin_step_percent=t2i_adapter_field.begin_step_percent,
+                    end_step_percent=t2i_adapter_field.end_step_percent,
+                    resize_mode=t2i_adapter_field.resize_mode,
+                )
+            )
+
     def prep_ip_adapter_image_prompts(
         self,
         context: InvocationContext,
@@ -845,6 +873,7 @@ def step_callback(state: PipelineIntermediateState) -> None:
             #    ext = extension_field.to_extension(exit_stack, context, ext_manager)
             #    ext_manager.add_extension(ext)
             self.parse_controlnet_field(exit_stack, context, self.control, ext_manager)
+            self.parse_t2i_adapter_field(exit_stack, context, self.t2i_adapter, ext_manager)
 
             # ext: t2i/ip adapter
             ext_manager.run_callback(ExtensionCallbackType.SETUP, denoise_ctx)

invokeai/backend/stable_diffusion/extensions/t2i_adapter.py

@@ -0,0 +1,120 @@
+from __future__ import annotations
+
+import math
+from typing import TYPE_CHECKING, List, Optional, Union
+
+import torch
+from diffusers import T2IAdapter
+from PIL.Image import Image
+
+from invokeai.app.util.controlnet_utils import prepare_control_image
+from invokeai.backend.model_manager import BaseModelType
+from invokeai.backend.stable_diffusion.diffusion.conditioning_data import ConditioningMode
+from invokeai.backend.stable_diffusion.extension_callback_type import ExtensionCallbackType
+from invokeai.backend.stable_diffusion.extensions.base import ExtensionBase, callback
+
+if TYPE_CHECKING:
+    from invokeai.app.invocations.model import ModelIdentifierField
+    from invokeai.app.services.shared.invocation_context import InvocationContext
+    from invokeai.app.util.controlnet_utils import CONTROLNET_RESIZE_VALUES
+    from invokeai.backend.stable_diffusion.denoise_context import DenoiseContext
+
+
+class T2IAdapterExt(ExtensionBase):
+    def __init__(
+        self,
+        node_context: InvocationContext,
+        model_id: ModelIdentifierField,
+        image: Image,
+        weight: Union[float, List[float]],
+        begin_step_percent: float,
+        end_step_percent: float,
+        resize_mode: CONTROLNET_RESIZE_VALUES,
+    ):
+        super().__init__()
+        self._node_context = node_context
+        self._model_id = model_id
+        self._image = image
+        self._weight = weight
+        self._resize_mode = resize_mode
+        self._begin_step_percent = begin_step_percent
+        self._end_step_percent = end_step_percent
+
+        self._adapter_state: Optional[List[torch.Tensor]] = None
+
+        # The max_unet_downscale is the maximum amount that the UNet model downscales the latent image internally.
+        model_config = self._node_context.models.get_config(self._model_id.key)
+        if model_config.base == BaseModelType.StableDiffusion1:
+            self._max_unet_downscale = 8
+        elif model_config.base == BaseModelType.StableDiffusionXL:
+            self._max_unet_downscale = 4
+        else:
+            raise ValueError(f"Unexpected T2I-Adapter base model type: '{model_config.base}'.")
+
+    @callback(ExtensionCallbackType.SETUP)
+    def setup(self, ctx: DenoiseContext):
+        t2i_model: T2IAdapter
+        with self._node_context.models.load(self._model_id) as t2i_model:
+            _, _, latents_height, latents_width = ctx.inputs.orig_latents.shape
+
+            self._adapter_state = self._run_model(
+                model=t2i_model,
+                image=self._image,
+                latents_height=latents_height,
+                latents_width=latents_width,
+            )
+
+    def _run_model(
+        self,
+        model: T2IAdapter,
+        image: Image,
+        latents_height: int,
+        latents_width: int,
+    ):
+        # Resize the T2I-Adapter input image.
+        # We select the resize dimensions so that after the T2I-Adapter's total_downscale_factor is applied, the
+        # result will match the latent image's dimensions after max_unet_downscale is applied.
+        input_height = latents_height // self._max_unet_downscale * model.total_downscale_factor
+        input_width = latents_width // self._max_unet_downscale * model.total_downscale_factor
+
+        # Note: We have hard-coded `do_classifier_free_guidance=False`. This is because we only want to prepare
+        # a single image. If CFG is enabled, we will duplicate the resultant tensor after applying the
+        # T2I-Adapter model.
+        #
+        # Note: We re-use the `prepare_control_image(...)` from ControlNet for T2I-Adapter, because it has many
+        # of the same requirements (e.g. preserving binary masks during resize).
+        t2i_image = prepare_control_image(
+            image=image,
+            do_classifier_free_guidance=False,
+            width=input_width,
+            height=input_height,
+            num_channels=model.config["in_channels"],
+            device=model.device,
+            dtype=model.dtype,
+            resize_mode=self._resize_mode,
+        )
+
+        return model(t2i_image)
+
+    @callback(ExtensionCallbackType.PRE_UNET)
+    def pre_unet_step(self, ctx: DenoiseContext):
+        # skip if model not active in current step
+        total_steps = len(ctx.inputs.timesteps)
+        first_step = math.floor(self._begin_step_percent * total_steps)
+        last_step = math.ceil(self._end_step_percent * total_steps)
+        if ctx.step_index < first_step or ctx.step_index > last_step:
+            return
+
+        weight = self._weight
+        if isinstance(weight, list):
+            weight = weight[ctx.step_index]
+
+        adapter_state = self._adapter_state
+        if ctx.conditioning_mode == ConditioningMode.Both:
+            adapter_state = [torch.cat([v] * 2) for v in adapter_state]
+
+        if ctx.unet_kwargs.down_intrablock_additional_residuals is None:
+            ctx.unet_kwargs.down_intrablock_additional_residuals = [v * weight for v in adapter_state]
+        else:
+            for i, value in enumerate(adapter_state):
+                ctx.unet_kwargs.down_intrablock_additional_residuals[i] += value * weight