chore: import upstream snapshot with attribution

invokeai/backend/stable_diffusion/extensions/preview.py

@@ -0,0 +1,63 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Callable, Optional
+
+import torch
+
+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.backend.stable_diffusion.denoise_context import DenoiseContext
+
+
+# TODO: change event to accept image instead of latents
+@dataclass
+class PipelineIntermediateState:
+    step: int
+    order: int
+    total_steps: int
+    timestep: int
+    latents: torch.Tensor
+    predicted_original: Optional[torch.Tensor] = None
+
+
+class PreviewExt(ExtensionBase):
+    def __init__(self, callback: Callable[[PipelineIntermediateState], None]):
+        super().__init__()
+        self.callback = callback
+
+    # do last so that all other changes shown
+    @callback(ExtensionCallbackType.PRE_DENOISE_LOOP, order=1000)
+    def initial_preview(self, ctx: DenoiseContext):
+        self.callback(
+            PipelineIntermediateState(
+                step=0,
+                order=ctx.scheduler.order,
+                total_steps=len(ctx.inputs.timesteps),
+                timestep=int(ctx.scheduler.config.num_train_timesteps),  # TODO: is there any code which uses it?
+                latents=ctx.latents,
+            )
+        )
+
+    # do last so that all other changes shown
+    @callback(ExtensionCallbackType.POST_STEP, order=1000)
+    def step_preview(self, ctx: DenoiseContext):
+        if hasattr(ctx.step_output, "denoised"):
+            predicted_original = ctx.step_output.denoised
+        elif hasattr(ctx.step_output, "pred_original_sample"):
+            predicted_original = ctx.step_output.pred_original_sample
+        else:
+            predicted_original = ctx.step_output.prev_sample
+
+        self.callback(
+            PipelineIntermediateState(
+                step=ctx.step_index,
+                order=ctx.scheduler.order,
+                total_steps=len(ctx.inputs.timesteps),
+                timestep=int(ctx.timestep),  # TODO: is there any code which uses it?
+                latents=ctx.step_output.prev_sample,
+                predicted_original=predicted_original,  # TODO: is there any reason for additional field?
+            )
+        )