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from typing import Union
import torch
from PIL import Image
from torchvision import transforms as tfms
from tqdm.auto import tqdm
from transformers import CLIPTextModel, CLIPTokenizer
from diffusers import (
AutoencoderKL,
DDIMScheduler,
DiffusionPipeline,
LMSDiscreteScheduler,
PNDMScheduler,
UNet2DConditionModel,
)
class MagicMixPipeline(DiffusionPipeline):
def __init__(
self,
vae: AutoencoderKL,
text_encoder: CLIPTextModel,
tokenizer: CLIPTokenizer,
unet: UNet2DConditionModel,
scheduler: Union[PNDMScheduler, LMSDiscreteScheduler, DDIMScheduler],
):
super().__init__()
self.register_modules(vae=vae, text_encoder=text_encoder, tokenizer=tokenizer, unet=unet, scheduler=scheduler)
# convert PIL image to latents
def encode(self, img):
with torch.no_grad():
latent = self.vae.encode(tfms.ToTensor()(img).unsqueeze(0).to(self.device) * 2 - 1)
latent = 0.18215 * latent.latent_dist.sample()
return latent
# convert latents to PIL image
def decode(self, latent):
latent = (1 / 0.18215) * latent
with torch.no_grad():
img = self.vae.decode(latent).sample
img = (img / 2 + 0.5).clamp(0, 1)
img = img.detach().cpu().permute(0, 2, 3, 1).numpy()
img = (img * 255).round().astype("uint8")
return Image.fromarray(img[0])
# convert prompt into text embeddings, also unconditional embeddings
def prep_text(self, prompt):
text_input = self.tokenizer(
prompt,
padding="max_length",
max_length=self.tokenizer.model_max_length,
truncation=True,
return_tensors="pt",
)
text_embedding = self.text_encoder(text_input.input_ids.to(self.device))[0]
uncond_input = self.tokenizer(
"",
padding="max_length",
max_length=self.tokenizer.model_max_length,
truncation=True,
return_tensors="pt",
)
uncond_embedding = self.text_encoder(uncond_input.input_ids.to(self.device))[0]
return torch.cat([uncond_embedding, text_embedding])
def __call__(
self,
img: Image.Image,
prompt: str,
kmin: float = 0.3,
kmax: float = 0.6,
mix_factor: float = 0.5,
seed: int = 42,
steps: int = 50,
guidance_scale: float = 7.5,
) -> Image.Image:
tmin = steps - int(kmin * steps)
tmax = steps - int(kmax * steps)
text_embeddings = self.prep_text(prompt)
self.scheduler.set_timesteps(steps)
width, height = img.size
encoded = self.encode(img)
torch.manual_seed(seed)
noise = torch.randn(
(1, self.unet.config.in_channels, height // 8, width // 8),
).to(self.device)
latents = self.scheduler.add_noise(
encoded,
noise,
timesteps=self.scheduler.timesteps[tmax],
)
input = torch.cat([latents] * 2)
input = self.scheduler.scale_model_input(input, self.scheduler.timesteps[tmax])
with torch.no_grad():
pred = self.unet(
input,
self.scheduler.timesteps[tmax],
encoder_hidden_states=text_embeddings,
).sample
pred_uncond, pred_text = pred.chunk(2)
pred = pred_uncond + guidance_scale * (pred_text - pred_uncond)
latents = self.scheduler.step(pred, self.scheduler.timesteps[tmax], latents).prev_sample
for i, t in enumerate(tqdm(self.scheduler.timesteps)):
if i > tmax:
if i < tmin: # layout generation phase
orig_latents = self.scheduler.add_noise(
encoded,
noise,
timesteps=t,
)
input = (
(mix_factor * latents) + (1 - mix_factor) * orig_latents
) # interpolating between layout noise and conditionally generated noise to preserve layout sematics
input = torch.cat([input] * 2)
else: # content generation phase
input = torch.cat([latents] * 2)
input = self.scheduler.scale_model_input(input, t)
with torch.no_grad():
pred = self.unet(
input,
t,
encoder_hidden_states=text_embeddings,
).sample
pred_uncond, pred_text = pred.chunk(2)
pred = pred_uncond + guidance_scale * (pred_text - pred_uncond)
latents = self.scheduler.step(pred, t, latents).prev_sample
return self.decode(latents)
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