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from typing import Optional
import torch
from PIL import Image
from tqdm.auto import tqdm
from transformers import CLIPTextModel, CLIPTokenizer
from diffusers import AutoencoderKL, DDIMScheduler, DiffusionPipeline, UNet2DConditionModel
from diffusers.image_processor import VaeImageProcessor
from diffusers.utils import (
deprecate,
)
class EDICTPipeline(DiffusionPipeline):
def __init__(
self,
vae: AutoencoderKL,
text_encoder: CLIPTextModel,
tokenizer: CLIPTokenizer,
unet: UNet2DConditionModel,
scheduler: DDIMScheduler,
mixing_coeff: float = 0.93,
leapfrog_steps: bool = True,
):
self.mixing_coeff = mixing_coeff
self.leapfrog_steps = leapfrog_steps
super().__init__()
self.register_modules(
vae=vae,
text_encoder=text_encoder,
tokenizer=tokenizer,
unet=unet,
scheduler=scheduler,
)
self.vae_scale_factor = 2 ** (len(self.vae.config.block_out_channels) - 1)
self.image_processor = VaeImageProcessor(vae_scale_factor=self.vae_scale_factor)
def _encode_prompt(
self, prompt: str, negative_prompt: Optional[str] = None, do_classifier_free_guidance: bool = False
):
text_inputs = self.tokenizer(
prompt,
padding="max_length",
max_length=self.tokenizer.model_max_length,
truncation=True,
return_tensors="pt",
)
prompt_embeds = self.text_encoder(text_inputs.input_ids.to(self.device)).last_hidden_state
prompt_embeds = prompt_embeds.to(dtype=self.text_encoder.dtype, device=self.device)
if do_classifier_free_guidance:
uncond_tokens = "" if negative_prompt is None else negative_prompt
uncond_input = self.tokenizer(
uncond_tokens,
padding="max_length",
max_length=self.tokenizer.model_max_length,
truncation=True,
return_tensors="pt",
)
negative_prompt_embeds = self.text_encoder(uncond_input.input_ids.to(self.device)).last_hidden_state
prompt_embeds = torch.cat([negative_prompt_embeds, prompt_embeds])
return prompt_embeds
def denoise_mixing_layer(self, x: torch.Tensor, y: torch.Tensor):
x = self.mixing_coeff * x + (1 - self.mixing_coeff) * y
y = self.mixing_coeff * y + (1 - self.mixing_coeff) * x
return [x, y]
def noise_mixing_layer(self, x: torch.Tensor, y: torch.Tensor):
y = (y - (1 - self.mixing_coeff) * x) / self.mixing_coeff
x = (x - (1 - self.mixing_coeff) * y) / self.mixing_coeff
return [x, y]
def _get_alpha_and_beta(self, t: torch.Tensor):
# as self.alphas_cumprod is always in cpu
t = int(t)
alpha_prod = self.scheduler.alphas_cumprod[t] if t >= 0 else self.scheduler.final_alpha_cumprod
return alpha_prod, 1 - alpha_prod
def noise_step(
self,
base: torch.Tensor,
model_input: torch.Tensor,
model_output: torch.Tensor,
timestep: torch.Tensor,
):
prev_timestep = timestep - self.scheduler.config.num_train_timesteps / self.scheduler.num_inference_steps
alpha_prod_t, beta_prod_t = self._get_alpha_and_beta(timestep)
alpha_prod_t_prev, beta_prod_t_prev = self._get_alpha_and_beta(prev_timestep)
a_t = (alpha_prod_t_prev / alpha_prod_t) ** 0.5
b_t = -a_t * (beta_prod_t**0.5) + beta_prod_t_prev**0.5
next_model_input = (base - b_t * model_output) / a_t
return model_input, next_model_input.to(base.dtype)
def denoise_step(
self,
base: torch.Tensor,
model_input: torch.Tensor,
model_output: torch.Tensor,
timestep: torch.Tensor,
):
prev_timestep = timestep - self.scheduler.config.num_train_timesteps / self.scheduler.num_inference_steps
alpha_prod_t, beta_prod_t = self._get_alpha_and_beta(timestep)
alpha_prod_t_prev, beta_prod_t_prev = self._get_alpha_and_beta(prev_timestep)
a_t = (alpha_prod_t_prev / alpha_prod_t) ** 0.5
b_t = -a_t * (beta_prod_t**0.5) + beta_prod_t_prev**0.5
next_model_input = a_t * base + b_t * model_output
return model_input, next_model_input.to(base.dtype)
@torch.no_grad()
def decode_latents(self, latents: torch.Tensor):
latents = 1 / self.vae.config.scaling_factor * latents
image = self.vae.decode(latents).sample
image = (image / 2 + 0.5).clamp(0, 1)
return image
@torch.no_grad()
def prepare_latents(
self,
image: Image.Image,
text_embeds: torch.Tensor,
timesteps: torch.Tensor,
guidance_scale: float,
generator: Optional[torch.Generator] = None,
):
do_classifier_free_guidance = guidance_scale > 1.0
image = image.to(device=self.device, dtype=text_embeds.dtype)
latent = self.vae.encode(image).latent_dist.sample(generator)
latent = self.vae.config.scaling_factor * latent
coupled_latents = [latent.clone(), latent.clone()]
for i, t in tqdm(enumerate(timesteps), total=len(timesteps)):
coupled_latents = self.noise_mixing_layer(x=coupled_latents[0], y=coupled_latents[1])
# j - model_input index, k - base index
for j in range(2):
k = j ^ 1
if self.leapfrog_steps:
if i % 2 == 0:
k, j = j, k
model_input = coupled_latents[j]
base = coupled_latents[k]
latent_model_input = torch.cat([model_input] * 2) if do_classifier_free_guidance else model_input
noise_pred = self.unet(latent_model_input, t, encoder_hidden_states=text_embeds).sample
if do_classifier_free_guidance:
noise_pred_uncond, noise_pred_text = noise_pred.chunk(2)
noise_pred = noise_pred_uncond + guidance_scale * (noise_pred_text - noise_pred_uncond)
base, model_input = self.noise_step(
base=base,
model_input=model_input,
model_output=noise_pred,
timestep=t,
)
coupled_latents[k] = model_input
return coupled_latents
@torch.no_grad()
def __call__(
self,
base_prompt: str,
target_prompt: str,
image: Image.Image,
guidance_scale: float = 3.0,
num_inference_steps: int = 50,
strength: float = 0.8,
negative_prompt: Optional[str] = None,
generator: Optional[torch.Generator] = None,
output_type: Optional[str] = "pil",
):
do_classifier_free_guidance = guidance_scale > 1.0
image = self.image_processor.preprocess(image)
base_embeds = self._encode_prompt(base_prompt, negative_prompt, do_classifier_free_guidance)
target_embeds = self._encode_prompt(target_prompt, negative_prompt, do_classifier_free_guidance)
self.scheduler.set_timesteps(num_inference_steps, self.device)
t_limit = num_inference_steps - int(num_inference_steps * strength)
fwd_timesteps = self.scheduler.timesteps[t_limit:]
bwd_timesteps = fwd_timesteps.flip(0)
coupled_latents = self.prepare_latents(image, base_embeds, bwd_timesteps, guidance_scale, generator)
for i, t in tqdm(enumerate(fwd_timesteps), total=len(fwd_timesteps)):
# j - model_input index, k - base index
for k in range(2):
j = k ^ 1
if self.leapfrog_steps:
if i % 2 == 1:
k, j = j, k
model_input = coupled_latents[j]
base = coupled_latents[k]
latent_model_input = torch.cat([model_input] * 2) if do_classifier_free_guidance else model_input
noise_pred = self.unet(latent_model_input, t, encoder_hidden_states=target_embeds).sample
if do_classifier_free_guidance:
noise_pred_uncond, noise_pred_text = noise_pred.chunk(2)
noise_pred = noise_pred_uncond + guidance_scale * (noise_pred_text - noise_pred_uncond)
base, model_input = self.denoise_step(
base=base,
model_input=model_input,
model_output=noise_pred,
timestep=t,
)
coupled_latents[k] = model_input
coupled_latents = self.denoise_mixing_layer(x=coupled_latents[0], y=coupled_latents[1])
# either one is fine
final_latent = coupled_latents[0]
if output_type not in ["latent", "pt", "np", "pil"]:
deprecation_message = (
f"the output_type {output_type} is outdated. Please make sure to set it to one of these instead: "
"`pil`, `np`, `pt`, `latent`"
)
deprecate("Unsupported output_type", "1.0.0", deprecation_message, standard_warn=False)
output_type = "np"
if output_type == "latent":
image = final_latent
else:
image = self.decode_latents(final_latent)
image = self.image_processor.postprocess(image, output_type=output_type)
return image
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