# Copyright 2025 The HuggingFace Team. All rights reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import inspect from typing import Any, List, Optional, Tuple, Union import numpy as np import torch from ...models import AutoencoderKL from ...schedulers import FlowMatchEulerDiscreteScheduler from ...utils import logging from ...utils.torch_utils import randn_tensor from ..modular_pipeline import ModularPipelineBlocks, PipelineState from ..modular_pipeline_utils import ComponentSpec, InputParam, OutputParam from .modular_pipeline import FluxModularPipeline logger = logging.get_logger(__name__) # pylint: disable=invalid-name # Copied from diffusers.pipelines.stable_diffusion.pipeline_stable_diffusion.retrieve_timesteps def retrieve_timesteps( scheduler, num_inference_steps: Optional[int] = None, device: Optional[Union[str, torch.device]] = None, timesteps: Optional[List[int]] = None, sigmas: Optional[List[float]] = None, **kwargs, ): r""" Calls the scheduler's `set_timesteps` method and retrieves timesteps from the scheduler after the call. Handles custom timesteps. Any kwargs will be supplied to `scheduler.set_timesteps`. Args: scheduler (`SchedulerMixin`): The scheduler to get timesteps from. num_inference_steps (`int`): The number of diffusion steps used when generating samples with a pre-trained model. If used, `timesteps` must be `None`. device (`str` or `torch.device`, *optional*): The device to which the timesteps should be moved to. If `None`, the timesteps are not moved. timesteps (`List[int]`, *optional*): Custom timesteps used to override the timestep spacing strategy of the scheduler. If `timesteps` is passed, `num_inference_steps` and `sigmas` must be `None`. sigmas (`List[float]`, *optional*): Custom sigmas used to override the timestep spacing strategy of the scheduler. If `sigmas` is passed, `num_inference_steps` and `timesteps` must be `None`. Returns: `Tuple[torch.Tensor, int]`: A tuple where the first element is the timestep schedule from the scheduler and the second element is the number of inference steps. """ if timesteps is not None and sigmas is not None: raise ValueError("Only one of `timesteps` or `sigmas` can be passed. Please choose one to set custom values") if timesteps is not None: accepts_timesteps = "timesteps" in set(inspect.signature(scheduler.set_timesteps).parameters.keys()) if not accepts_timesteps: raise ValueError( f"The current scheduler class {scheduler.__class__}'s `set_timesteps` does not support custom" f" timestep schedules. Please check whether you are using the correct scheduler." ) scheduler.set_timesteps(timesteps=timesteps, device=device, **kwargs) timesteps = scheduler.timesteps num_inference_steps = len(timesteps) elif sigmas is not None: accept_sigmas = "sigmas" in set(inspect.signature(scheduler.set_timesteps).parameters.keys()) if not accept_sigmas: raise ValueError( f"The current scheduler class {scheduler.__class__}'s `set_timesteps` does not support custom" f" sigmas schedules. Please check whether you are using the correct scheduler." ) scheduler.set_timesteps(sigmas=sigmas, device=device, **kwargs) timesteps = scheduler.timesteps num_inference_steps = len(timesteps) else: scheduler.set_timesteps(num_inference_steps, device=device, **kwargs) timesteps = scheduler.timesteps return timesteps, num_inference_steps # Copied from diffusers.pipelines.flux.pipeline_flux.calculate_shift def calculate_shift( image_seq_len, base_seq_len: int = 256, max_seq_len: int = 4096, base_shift: float = 0.5, max_shift: float = 1.15, ): m = (max_shift - base_shift) / (max_seq_len - base_seq_len) b = base_shift - m * base_seq_len mu = image_seq_len * m + b return mu # Adapted from the original implementation. def prepare_latents_img2img( vae, scheduler, image, timestep, batch_size, num_channels_latents, height, width, dtype, device, generator ): 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." ) vae_scale_factor = 2 ** (len(vae.config.block_out_channels) - 1) latent_channels = vae.config.latent_channels # VAE applies 8x compression on images but we must also account for packing which requires # latent height and width to be divisible by 2. height = 2 * (int(height) // (vae_scale_factor * 2)) width = 2 * (int(width) // (vae_scale_factor * 2)) shape = (batch_size, num_channels_latents, height, width) latent_image_ids = _prepare_latent_image_ids(batch_size, height // 2, width // 2, device, dtype) image = image.to(device=device, dtype=dtype) if image.shape[1] != latent_channels: image_latents = _encode_vae_image(image=image, generator=generator) else: image_latents = image if batch_size > image_latents.shape[0] and batch_size % image_latents.shape[0] == 0: # expand init_latents for batch_size additional_image_per_prompt = batch_size // image_latents.shape[0] image_latents = torch.cat([image_latents] * additional_image_per_prompt, dim=0) elif batch_size > image_latents.shape[0] and batch_size % image_latents.shape[0] != 0: raise ValueError( f"Cannot duplicate `image` of batch size {image_latents.shape[0]} to {batch_size} text prompts." ) else: image_latents = torch.cat([image_latents], dim=0) noise = randn_tensor(shape, generator=generator, device=device, dtype=dtype) latents = scheduler.scale_noise(image_latents, timestep, noise) latents = _pack_latents(latents, batch_size, num_channels_latents, height, width) return latents, latent_image_ids # Copied from diffusers.pipelines.stable_diffusion.pipeline_stable_diffusion_img2img.retrieve_latents def retrieve_latents( encoder_output: torch.Tensor, generator: Optional[torch.Generator] = None, sample_mode: str = "sample" ): if hasattr(encoder_output, "latent_dist") and sample_mode == "sample": return encoder_output.latent_dist.sample(generator) elif hasattr(encoder_output, "latent_dist") and sample_mode == "argmax": return encoder_output.latent_dist.mode() elif hasattr(encoder_output, "latents"): return encoder_output.latents else: raise AttributeError("Could not access latents of provided encoder_output") def _pack_latents(latents, batch_size, num_channels_latents, height, width): latents = latents.view(batch_size, num_channels_latents, height // 2, 2, width // 2, 2) latents = latents.permute(0, 2, 4, 1, 3, 5) latents = latents.reshape(batch_size, (height // 2) * (width // 2), num_channels_latents * 4) return latents def _prepare_latent_image_ids(batch_size, height, width, device, dtype): latent_image_ids = torch.zeros(height, width, 3) latent_image_ids[..., 1] = latent_image_ids[..., 1] + torch.arange(height)[:, None] latent_image_ids[..., 2] = latent_image_ids[..., 2] + torch.arange(width)[None, :] latent_image_id_height, latent_image_id_width, latent_image_id_channels = latent_image_ids.shape latent_image_ids = latent_image_ids.reshape( latent_image_id_height * latent_image_id_width, latent_image_id_channels ) return latent_image_ids.to(device=device, dtype=dtype) # Cannot use "# Copied from" because it introduces weird indentation errors. def _encode_vae_image(vae, image: torch.Tensor, generator: torch.Generator): if isinstance(generator, list): image_latents = [ retrieve_latents(vae.encode(image[i : i + 1]), generator=generator[i]) for i in range(image.shape[0]) ] image_latents = torch.cat(image_latents, dim=0) else: image_latents = retrieve_latents(vae.encode(image), generator=generator) image_latents = (image_latents - vae.config.shift_factor) * vae.config.scaling_factor return image_latents def _get_initial_timesteps_and_optionals( transformer, scheduler, batch_size, height, width, vae_scale_factor, num_inference_steps, guidance_scale, sigmas, device, ): image_seq_len = (int(height) // vae_scale_factor // 2) * (int(width) // vae_scale_factor // 2) sigmas = np.linspace(1.0, 1 / num_inference_steps, num_inference_steps) if sigmas is None else sigmas if hasattr(scheduler.config, "use_flow_sigmas") and scheduler.config.use_flow_sigmas: sigmas = None mu = calculate_shift( image_seq_len, scheduler.config.get("base_image_seq_len", 256), scheduler.config.get("max_image_seq_len", 4096), scheduler.config.get("base_shift", 0.5), scheduler.config.get("max_shift", 1.15), ) timesteps, num_inference_steps = retrieve_timesteps(scheduler, num_inference_steps, device, sigmas=sigmas, mu=mu) if transformer.config.guidance_embeds: guidance = torch.full([1], guidance_scale, device=device, dtype=torch.float32) guidance = guidance.expand(batch_size) else: guidance = None return timesteps, num_inference_steps, sigmas, guidance class FluxInputStep(ModularPipelineBlocks): model_name = "flux" @property def description(self) -> str: return ( "Input processing step that:\n" " 1. Determines `batch_size` and `dtype` based on `prompt_embeds`\n" " 2. Adjusts input tensor shapes based on `batch_size` (number of prompts) and `num_images_per_prompt`\n\n" "All input tensors are expected to have either batch_size=1 or match the batch_size\n" "of prompt_embeds. The tensors will be duplicated across the batch dimension to\n" "have a final batch_size of batch_size * num_images_per_prompt." ) @property def inputs(self) -> List[InputParam]: return [ InputParam("num_images_per_prompt", default=1), InputParam( "prompt_embeds", required=True, type_hint=torch.Tensor, description="Pre-generated text embeddings. Can be generated from text_encoder step.", ), InputParam( "pooled_prompt_embeds", type_hint=torch.Tensor, description="Pre-generated pooled text embeddings. Can be generated from text_encoder step.", ), # TODO: support negative embeddings? ] @property def intermediate_outputs(self) -> List[str]: return [ OutputParam( "batch_size", type_hint=int, description="Number of prompts, the final batch size of model inputs should be batch_size * num_images_per_prompt", ), OutputParam( "dtype", type_hint=torch.dtype, description="Data type of model tensor inputs (determined by `prompt_embeds`)", ), OutputParam( "prompt_embeds", type_hint=torch.Tensor, description="text embeddings used to guide the image generation", ), OutputParam( "pooled_prompt_embeds", type_hint=torch.Tensor, description="pooled text embeddings used to guide the image generation", ), # TODO: support negative embeddings? ] def check_inputs(self, components, block_state): if block_state.prompt_embeds is not None and block_state.pooled_prompt_embeds is not None: if block_state.prompt_embeds.shape[0] != block_state.pooled_prompt_embeds.shape[0]: raise ValueError( "`prompt_embeds` and `pooled_prompt_embeds` must have the same batch size when passed directly, but" f" got: `prompt_embeds` {block_state.prompt_embeds.shape} != `pooled_prompt_embeds`" f" {block_state.pooled_prompt_embeds.shape}." ) @torch.no_grad() def __call__(self, components: FluxModularPipeline, state: PipelineState) -> PipelineState: # TODO: consider adding negative embeddings? block_state = self.get_block_state(state) self.check_inputs(components, block_state) block_state.batch_size = block_state.prompt_embeds.shape[0] block_state.dtype = block_state.prompt_embeds.dtype _, seq_len, _ = block_state.prompt_embeds.shape block_state.prompt_embeds = block_state.prompt_embeds.repeat(1, block_state.num_images_per_prompt, 1) block_state.prompt_embeds = block_state.prompt_embeds.view( block_state.batch_size * block_state.num_images_per_prompt, seq_len, -1 ) self.set_block_state(state, block_state) return components, state class FluxSetTimestepsStep(ModularPipelineBlocks): model_name = "flux" @property def expected_components(self) -> List[ComponentSpec]: return [ComponentSpec("scheduler", FlowMatchEulerDiscreteScheduler)] @property def description(self) -> str: return "Step that sets the scheduler's timesteps for inference" @property def inputs(self) -> List[InputParam]: return [ InputParam("num_inference_steps", default=50), InputParam("timesteps"), InputParam("sigmas"), InputParam("guidance_scale", default=3.5), InputParam("latents", type_hint=torch.Tensor), InputParam("num_images_per_prompt", default=1), InputParam("height", type_hint=int), InputParam("width", type_hint=int), InputParam( "batch_size", required=True, type_hint=int, description="Number of prompts, the final batch size of model inputs should be `batch_size * num_images_per_prompt`. Can be generated in input step.", ), ] @property def intermediate_outputs(self) -> List[OutputParam]: return [ OutputParam("timesteps", type_hint=torch.Tensor, description="The timesteps to use for inference"), OutputParam( "num_inference_steps", type_hint=int, description="The number of denoising steps to perform at inference time", ), OutputParam("guidance", type_hint=torch.Tensor, description="Optional guidance to be used."), ] @torch.no_grad() def __call__(self, components: FluxModularPipeline, state: PipelineState) -> PipelineState: block_state = self.get_block_state(state) block_state.device = components._execution_device scheduler = components.scheduler transformer = components.transformer batch_size = block_state.batch_size * block_state.num_images_per_prompt timesteps, num_inference_steps, sigmas, guidance = _get_initial_timesteps_and_optionals( transformer, scheduler, batch_size, block_state.height, block_state.width, components.vae_scale_factor, block_state.num_inference_steps, block_state.guidance_scale, block_state.sigmas, block_state.device, ) block_state.timesteps = timesteps block_state.num_inference_steps = num_inference_steps block_state.sigmas = sigmas block_state.guidance = guidance self.set_block_state(state, block_state) return components, state class FluxImg2ImgSetTimestepsStep(ModularPipelineBlocks): model_name = "flux" @property def expected_components(self) -> List[ComponentSpec]: return [ComponentSpec("scheduler", FlowMatchEulerDiscreteScheduler)] @property def description(self) -> str: return "Step that sets the scheduler's timesteps for inference" @property def inputs(self) -> List[InputParam]: return [ InputParam("num_inference_steps", default=50), InputParam("timesteps"), InputParam("sigmas"), InputParam("strength", default=0.6), InputParam("guidance_scale", default=3.5), InputParam("num_images_per_prompt", default=1), InputParam("height", type_hint=int), InputParam("width", type_hint=int), InputParam( "batch_size", required=True, type_hint=int, description="Number of prompts, the final batch size of model inputs should be `batch_size * num_images_per_prompt`. Can be generated in input step.", ), ] @property def intermediate_outputs(self) -> List[OutputParam]: return [ OutputParam("timesteps", type_hint=torch.Tensor, description="The timesteps to use for inference"), OutputParam( "num_inference_steps", type_hint=int, description="The number of denoising steps to perform at inference time", ), OutputParam( "latent_timestep", type_hint=torch.Tensor, description="The timestep that represents the initial noise level for image-to-image generation", ), OutputParam("guidance", type_hint=torch.Tensor, description="Optional guidance to be used."), ] @staticmethod # Copied from diffusers.pipelines.stable_diffusion_3.pipeline_stable_diffusion_3_img2img.StableDiffusion3Img2ImgPipeline.get_timesteps with self.scheduler->scheduler def get_timesteps(scheduler, num_inference_steps, strength, device): # get the original timestep using init_timestep init_timestep = min(num_inference_steps * strength, num_inference_steps) t_start = int(max(num_inference_steps - init_timestep, 0)) timesteps = scheduler.timesteps[t_start * scheduler.order :] if hasattr(scheduler, "set_begin_index"): scheduler.set_begin_index(t_start * scheduler.order) return timesteps, num_inference_steps - t_start @torch.no_grad() def __call__(self, components: FluxModularPipeline, state: PipelineState) -> PipelineState: block_state = self.get_block_state(state) block_state.device = components._execution_device block_state.height = block_state.height or components.default_height block_state.width = block_state.width or components.default_width scheduler = components.scheduler transformer = components.transformer batch_size = block_state.batch_size * block_state.num_images_per_prompt timesteps, num_inference_steps, sigmas, guidance = _get_initial_timesteps_and_optionals( transformer, scheduler, batch_size, block_state.height, block_state.width, components.vae_scale_factor, block_state.num_inference_steps, block_state.guidance_scale, block_state.sigmas, block_state.device, ) timesteps, num_inference_steps = self.get_timesteps( scheduler, num_inference_steps, block_state.strength, block_state.device ) block_state.timesteps = timesteps block_state.num_inference_steps = num_inference_steps block_state.sigmas = sigmas block_state.guidance = guidance block_state.latent_timestep = timesteps[:1].repeat(batch_size) self.set_block_state(state, block_state) return components, state class FluxPrepareLatentsStep(ModularPipelineBlocks): model_name = "flux" @property def expected_components(self) -> List[ComponentSpec]: return [] @property def description(self) -> str: return "Prepare latents step that prepares the latents for the text-to-image generation process" @property def inputs(self) -> List[InputParam]: return [ InputParam("height", type_hint=int), InputParam("width", type_hint=int), InputParam("latents", type_hint=Optional[torch.Tensor]), InputParam("num_images_per_prompt", type_hint=int, default=1), InputParam("generator"), InputParam( "batch_size", required=True, type_hint=int, description="Number of prompts, the final batch size of model inputs should be `batch_size * num_images_per_prompt`. Can be generated in input step.", ), InputParam("dtype", type_hint=torch.dtype, description="The dtype of the model inputs"), ] @property def intermediate_outputs(self) -> List[OutputParam]: return [ OutputParam( "latents", type_hint=torch.Tensor, description="The initial latents to use for the denoising process" ), OutputParam( "latent_image_ids", type_hint=torch.Tensor, description="IDs computed from the image sequence needed for RoPE", ), ] @staticmethod def check_inputs(components, block_state): if (block_state.height is not None and block_state.height % (components.vae_scale_factor * 2) != 0) or ( block_state.width is not None and block_state.width % (components.vae_scale_factor * 2) != 0 ): logger.warning( f"`height` and `width` have to be divisible by {components.vae_scale_factor} but are {block_state.height} and {block_state.width}." ) @staticmethod def prepare_latents( comp, batch_size, num_channels_latents, height, width, dtype, device, generator, latents=None, ): # Couldn't use the `prepare_latents` method directly from Flux because I decided to copy over # the packing methods here. So, for example, `comp._pack_latents()` won't work if we were # to go with the "# Copied from ..." approach. Or maybe there's a way? # VAE applies 8x compression on images but we must also account for packing which requires # latent height and width to be divisible by 2. height = 2 * (int(height) // (comp.vae_scale_factor * 2)) width = 2 * (int(width) // (comp.vae_scale_factor * 2)) shape = (batch_size, num_channels_latents, height, width) if latents is not None: latent_image_ids = _prepare_latent_image_ids(batch_size, height // 2, width // 2, device, dtype) return latents.to(device=device, dtype=dtype), latent_image_ids 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." ) latents = randn_tensor(shape, generator=generator, device=device, dtype=dtype) latents = _pack_latents(latents, batch_size, num_channels_latents, height, width) latent_image_ids = _prepare_latent_image_ids(batch_size, height // 2, width // 2, device, dtype) return latents, latent_image_ids @torch.no_grad() def __call__(self, components: FluxModularPipeline, state: PipelineState) -> PipelineState: block_state = self.get_block_state(state) block_state.height = block_state.height or components.default_height block_state.width = block_state.width or components.default_width block_state.device = components._execution_device block_state.dtype = torch.bfloat16 # TODO: okay to hardcode this? block_state.num_channels_latents = components.num_channels_latents self.check_inputs(components, block_state) batch_size = block_state.batch_size * block_state.num_images_per_prompt block_state.latents, block_state.latent_image_ids = self.prepare_latents( components, batch_size, block_state.num_channels_latents, block_state.height, block_state.width, block_state.dtype, block_state.device, block_state.generator, block_state.latents, ) self.set_block_state(state, block_state) return components, state class FluxImg2ImgPrepareLatentsStep(ModularPipelineBlocks): model_name = "flux" @property def expected_components(self) -> List[ComponentSpec]: return [ComponentSpec("vae", AutoencoderKL), ComponentSpec("scheduler", FlowMatchEulerDiscreteScheduler)] @property def description(self) -> str: return "Step that prepares the latents for the image-to-image generation process" @property def inputs(self) -> List[Tuple[str, Any]]: return [ InputParam("height", type_hint=int), InputParam("width", type_hint=int), InputParam("latents", type_hint=Optional[torch.Tensor]), InputParam("num_images_per_prompt", type_hint=int, default=1), InputParam("generator"), InputParam( "image_latents", required=True, type_hint=torch.Tensor, description="The latents representing the reference image for image-to-image/inpainting generation. Can be generated in vae_encode step.", ), InputParam( "latent_timestep", required=True, type_hint=torch.Tensor, description="The timestep that represents the initial noise level for image-to-image/inpainting generation. Can be generated in set_timesteps step.", ), InputParam( "batch_size", required=True, type_hint=int, description="Number of prompts, the final batch size of model inputs should be batch_size * num_images_per_prompt. Can be generated in input step.", ), InputParam("dtype", required=True, type_hint=torch.dtype, description="The dtype of the model inputs"), ] @property def intermediate_outputs(self) -> List[OutputParam]: return [ OutputParam( "latents", type_hint=torch.Tensor, description="The initial latents to use for the denoising process" ), OutputParam( "latent_image_ids", type_hint=torch.Tensor, description="IDs computed from the image sequence needed for RoPE", ), ] @torch.no_grad() def __call__(self, components: FluxModularPipeline, state: PipelineState) -> PipelineState: block_state = self.get_block_state(state) block_state.device = components._execution_device block_state.dtype = torch.bfloat16 # TODO: okay to hardcode this? block_state.num_channels_latents = components.num_channels_latents block_state.dtype = block_state.dtype if block_state.dtype is not None else components.vae.dtype block_state.device = components._execution_device # TODO: implement `check_inputs` batch_size = block_state.batch_size * block_state.num_images_per_prompt if block_state.latents is None: block_state.latents, block_state.latent_image_ids = prepare_latents_img2img( components.vae, components.scheduler, block_state.image_latents, block_state.latent_timestep, batch_size, block_state.num_channels_latents, block_state.height, block_state.width, block_state.dtype, block_state.device, block_state.generator, ) self.set_block_state(state, block_state) return components, state