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from typing import List, Optional, Tuple, Union
import torch
from diffusers import DiffusionPipeline
from diffusers.configuration_utils import ConfigMixin
from diffusers.pipeline_utils import ImagePipelineOutput
from diffusers.schedulers.scheduling_utils import SchedulerMixin
class IADBScheduler(SchedulerMixin, ConfigMixin):
"""
IADBScheduler is a scheduler for the Iterative α-(de)Blending denoising method. It is simple and minimalist.
For more details, see the original paper: https://arxiv.org/abs/2305.03486 and the blog post: https://ggx-research.github.io/publication/2023/05/10/publication-iadb.html
"""
def step(
self,
model_output: torch.FloatTensor,
timestep: int,
x_alpha: torch.FloatTensor,
) -> torch.FloatTensor:
"""
Predict the sample at the previous timestep by reversing the ODE. Core function to propagate the diffusion
process from the learned model outputs (most often the predicted noise).
Args:
model_output (`torch.FloatTensor`): direct output from learned diffusion model. It is the direction from x0 to x1.
timestep (`float`): current timestep in the diffusion chain.
x_alpha (`torch.FloatTensor`): x_alpha sample for the current timestep
Returns:
`torch.FloatTensor`: the sample at the previous timestep
"""
if self.num_inference_steps is None:
raise ValueError(
"Number of inference steps is 'None', you need to run 'set_timesteps' after creating the scheduler"
)
alpha = timestep / self.num_inference_steps
alpha_next = (timestep + 1) / self.num_inference_steps
d = model_output
x_alpha = x_alpha + (alpha_next - alpha) * d
return x_alpha
def set_timesteps(self, num_inference_steps: int):
self.num_inference_steps = num_inference_steps
def add_noise(
self,
original_samples: torch.FloatTensor,
noise: torch.FloatTensor,
alpha: torch.FloatTensor,
) -> torch.FloatTensor:
return original_samples * alpha + noise * (1 - alpha)
def __len__(self):
return self.config.num_train_timesteps
class IADBPipeline(DiffusionPipeline):
r"""
This model inherits from [`DiffusionPipeline`]. Check the superclass documentation for the generic methods the
library implements for all the pipelines (such as downloading or saving, running on a particular device, etc.)
Parameters:
unet ([`UNet2DModel`]): U-Net architecture to denoise the encoded image.
scheduler ([`SchedulerMixin`]):
A scheduler to be used in combination with `unet` to denoise the encoded image. Can be one of
[`DDPMScheduler`], or [`DDIMScheduler`].
"""
def __init__(self, unet, scheduler):
super().__init__()
self.register_modules(unet=unet, scheduler=scheduler)
@torch.no_grad()
def __call__(
self,
batch_size: int = 1,
generator: Optional[Union[torch.Generator, List[torch.Generator]]] = None,
num_inference_steps: int = 50,
output_type: Optional[str] = "pil",
return_dict: bool = True,
) -> Union[ImagePipelineOutput, Tuple]:
r"""
Args:
batch_size (`int`, *optional*, defaults to 1):
The number of images to generate.
num_inference_steps (`int`, *optional*, defaults to 50):
The number of denoising steps. More denoising steps usually lead to a higher quality image at the
expense of slower inference.
output_type (`str`, *optional*, defaults to `"pil"`):
The output format of the generate image. Choose between
[PIL](https://pillow.readthedocs.io/en/stable/): `PIL.Image.Image` or `np.array`.
return_dict (`bool`, *optional*, defaults to `True`):
Whether or not to return a [`~pipelines.ImagePipelineOutput`] instead of a plain tuple.
Returns:
[`~pipelines.ImagePipelineOutput`] or `tuple`: [`~pipelines.utils.ImagePipelineOutput`] if `return_dict` is
True, otherwise a `tuple. When returning a tuple, the first element is a list with the generated images.
"""
# Sample gaussian noise to begin loop
if isinstance(self.unet.config.sample_size, int):
image_shape = (
batch_size,
self.unet.config.in_channels,
self.unet.config.sample_size,
self.unet.config.sample_size,
)
else:
image_shape = (batch_size, self.unet.config.in_channels, *self.unet.config.sample_size)
if isinstance(generator, list) and len(generator) != batch_size:
raise ValueError(
f"You have passed a list of generators of length {len(generator)}, but requested an effective batch"
f" size of {batch_size}. Make sure the batch size matches the length of the generators."
)
image = torch.randn(image_shape, generator=generator, device=self.device, dtype=self.unet.dtype)
# set step values
self.scheduler.set_timesteps(num_inference_steps)
x_alpha = image.clone()
for t in self.progress_bar(range(num_inference_steps)):
alpha = t / num_inference_steps
# 1. predict noise model_output
model_output = self.unet(x_alpha, torch.tensor(alpha, device=x_alpha.device)).sample
# 2. step
x_alpha = self.scheduler.step(model_output, t, x_alpha)
image = (x_alpha * 0.5 + 0.5).clamp(0, 1)
image = image.cpu().permute(0, 2, 3, 1).numpy()
if output_type == "pil":
image = self.numpy_to_pil(image)
if not return_dict:
return (image,)
return ImagePipelineOutput(images=image)
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