# Copyright 2025 Alibaba Z-Image Team and 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 import numpy as np import PIL from dataclasses import dataclass from typing import Any, Callable, Dict, List, Optional, Tuple, Union import torch import torch.nn.functional as F from diffusers.image_processor import VaeImageProcessor from diffusers.loaders import FromSingleFileMixin from diffusers.pipelines.pipeline_utils import DiffusionPipeline from diffusers.schedulers import FlowMatchEulerDiscreteScheduler from diffusers.utils import (BaseOutput, is_torch_xla_available, logging, replace_example_docstring) from diffusers.utils.torch_utils import randn_tensor from transformers import AutoTokenizer, PreTrainedModel from ..models import AutoencoderKL, ZImageTransformer2DModel logger = logging.get_logger(__name__) # pylint: disable=invalid-name EXAMPLE_DOC_STRING = """ Examples: ```py >>> import torch >>> from diffusers import ZImagePipeline >>> pipe = ZImagePipeline.from_pretrained("Z-a-o/Z-Image-Turbo", torch_dtype=torch.bfloat16) >>> pipe.to("cuda") >>> # Optionally, set the attention backend to flash-attn 2 or 3, default is SDPA in PyTorch. >>> # (1) Use flash attention 2 >>> # pipe.transformer.set_attention_backend("flash") >>> # (2) Use flash attention 3 >>> # pipe.transformer.set_attention_backend("_flash_3") >>> prompt = "一幅为名为“造相「Z-IMAGE-TURBO」”的项目设计的创意海报。画面巧妙地将文字概念视觉化：一辆复古蒸汽小火车化身为巨大的拉链头，正拉开厚厚的冬日积雪，展露出一个生机盎然的春天。" >>> image = pipe( diffusers. prompt, diffusers. height=1024, diffusers. width=1024, diffusers. num_inference_steps=9, diffusers. guidance_scale=0.0, diffusers. generator=torch.Generator("cuda").manual_seed(42), diffusers. ).images[0] >>> image.save("zimage.png") ``` """ # 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 # 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 @dataclass class ZImagePipelineOutput(BaseOutput): """ Output class for Z-Image image generation pipelines. Args: images (`List[PIL.Image.Image]` or `torch.Tensor` or `np.ndarray`) List of denoised PIL images of length `batch_size` or numpy array or torch tensor of shape `(batch_size, height, width, num_channels)`. PIL images or numpy array present the denoised images of the diffusion pipeline. Torch tensors can represent either the denoised images or the intermediate latents ready to be passed to the decoder. """ images: Union[List[PIL.Image.Image], np.ndarray] class ZImageControlPipeline(DiffusionPipeline, FromSingleFileMixin): model_cpu_offload_seq = "text_encoder->transformer->vae" _optional_components = [] _callback_tensor_inputs = ["latents", "prompt_embeds"] def __init__( self, scheduler: FlowMatchEulerDiscreteScheduler, vae: AutoencoderKL, text_encoder: PreTrainedModel, tokenizer: AutoTokenizer, transformer: ZImageTransformer2DModel, ): super().__init__() self.register_modules( vae=vae, text_encoder=text_encoder, tokenizer=tokenizer, scheduler=scheduler, transformer=transformer, ) self.vae_scale_factor = ( 2 ** (len(self.vae.config.block_out_channels) - 1) if hasattr(self, "vae") and self.vae is not None else 8 ) self.image_processor = VaeImageProcessor(vae_scale_factor=self.vae_scale_factor * 2) self.mask_processor = VaeImageProcessor( vae_scale_factor=self.vae_scale_factor, do_normalize=False, do_binarize=True, do_convert_grayscale=True ) def encode_prompt( self, prompt: Union[str, List[str]], device: Optional[torch.device] = None, do_classifier_free_guidance: bool = True, negative_prompt: Optional[Union[str, List[str]]] = None, prompt_embeds: Optional[List[torch.FloatTensor]] = None, negative_prompt_embeds: Optional[torch.FloatTensor] = None, max_sequence_length: int = 512, ): prompt = [prompt] if isinstance(prompt, str) else prompt prompt_embeds = self._encode_prompt( prompt=prompt, device=device, prompt_embeds=prompt_embeds, max_sequence_length=max_sequence_length, ) if do_classifier_free_guidance: if negative_prompt is None: negative_prompt = ["" for _ in prompt] else: negative_prompt = [negative_prompt] if isinstance(negative_prompt, str) else negative_prompt assert len(prompt) == len(negative_prompt) negative_prompt_embeds = self._encode_prompt( prompt=negative_prompt, device=device, prompt_embeds=negative_prompt_embeds, max_sequence_length=max_sequence_length, ) else: negative_prompt_embeds = [] return prompt_embeds, negative_prompt_embeds def _encode_prompt( self, prompt: Union[str, List[str]], device: Optional[torch.device] = None, prompt_embeds: Optional[List[torch.FloatTensor]] = None, max_sequence_length: int = 512, ) -> List[torch.FloatTensor]: device = device or self._execution_device if prompt_embeds is not None: return prompt_embeds if isinstance(prompt, str): prompt = [prompt] for i, prompt_item in enumerate(prompt): messages = [ {"role": "user", "content": prompt_item}, ] prompt_item = self.tokenizer.apply_chat_template( messages, tokenize=False, add_generation_prompt=True, enable_thinking=True, ) prompt[i] = prompt_item text_inputs = self.tokenizer( prompt, padding="max_length", max_length=max_sequence_length, truncation=True, return_tensors="pt", ) text_input_ids = text_inputs.input_ids.to(device) prompt_masks = text_inputs.attention_mask.to(device).bool() prompt_embeds = self.text_encoder( input_ids=text_input_ids, attention_mask=prompt_masks, output_hidden_states=True, ).hidden_states[-2] embeddings_list = [] for i in range(len(prompt_embeds)): embeddings_list.append(prompt_embeds[i][prompt_masks[i]]) return embeddings_list def prepare_latents( self, batch_size, num_channels_latents, height, width, dtype, device, generator, latents=None, ): height = 2 * (int(height) // (self.vae_scale_factor * 2)) width = 2 * (int(width) // (self.vae_scale_factor * 2)) shape = (batch_size, num_channels_latents, height, width) if latents is None: latents = randn_tensor(shape, generator=generator, device=device, dtype=dtype) else: if latents.shape != shape: raise ValueError(f"Unexpected latents shape, got {latents.shape}, expected {shape}") latents = latents.to(device) return latents @property def guidance_scale(self): return self._guidance_scale @property def do_classifier_free_guidance(self): return self._guidance_scale > 1 @property def joint_attention_kwargs(self): return self._joint_attention_kwargs @property def num_timesteps(self): return self._num_timesteps @property def interrupt(self): return self._interrupt @torch.no_grad() @replace_example_docstring(EXAMPLE_DOC_STRING) def __call__( self, prompt: Union[str, List[str]] = None, height: Optional[int] = None, width: Optional[int] = None, control_image: Union[torch.FloatTensor] = None, control_context_scale: float = 1.0, num_inference_steps: int = 50, sigmas: Optional[List[float]] = None, guidance_scale: float = 5.0, cfg_normalization: bool = False, cfg_truncation: float = 1.0, negative_prompt: Optional[Union[str, List[str]]] = None, num_images_per_prompt: Optional[int] = 1, generator: Optional[Union[torch.Generator, List[torch.Generator]]] = None, latents: Optional[torch.FloatTensor] = None, prompt_embeds: Optional[List[torch.FloatTensor]] = None, negative_prompt_embeds: Optional[List[torch.FloatTensor]] = None, output_type: Optional[str] = "pil", return_dict: bool = True, joint_attention_kwargs: Optional[Dict[str, Any]] = None, callback_on_step_end: Optional[Callable[[int, int, Dict], None]] = None, callback_on_step_end_tensor_inputs: List[str] = ["latents"], max_sequence_length: int = 512, ): r""" Function invoked when calling the pipeline for generation. Args: prompt (`str` or `List[str]`, *optional*): The prompt or prompts to guide the image generation. If not defined, one has to pass `prompt_embeds`. instead. height (`int`, *optional*, defaults to 1024): The height in pixels of the generated image. width (`int`, *optional*, defaults to 1024): The width in pixels of the generated image. 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. sigmas (`List[float]`, *optional*): Custom sigmas to use for the denoising process with schedulers which support a `sigmas` argument in their `set_timesteps` method. If not defined, the default behavior when `num_inference_steps` is passed will be used. guidance_scale (`float`, *optional*, defaults to 5.0): Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598). `guidance_scale` is defined as `w` of equation 2. of [Imagen Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting `guidance_scale > 1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`, usually at the expense of lower image quality. cfg_normalization (`bool`, *optional*, defaults to False): Whether to apply configuration normalization. cfg_truncation (`float`, *optional*, defaults to 1.0): The truncation value for configuration. negative_prompt (`str` or `List[str]`, *optional*): The prompt or prompts not to guide the image generation. If not defined, one has to pass `negative_prompt_embeds` instead. Ignored when not using guidance (i.e., ignored if `guidance_scale` is less than `1`). num_images_per_prompt (`int`, *optional*, defaults to 1): The number of images to generate per prompt. generator (`torch.Generator` or `List[torch.Generator]`, *optional*): One or a list of [torch generator(s)](https://pytorch.org/docs/stable/generated/torch.Generator.html) to make generation deterministic. latents (`torch.FloatTensor`, *optional*): Pre-generated noisy latents, sampled from a Gaussian distribution, to be used as inputs for image generation. Can be used to tweak the same generation with different prompts. If not provided, a latents tensor will be generated by sampling using the supplied random `generator`. prompt_embeds (`List[torch.FloatTensor]`, *optional*): Pre-generated text embeddings. Can be used to easily tweak text inputs, *e.g.* prompt weighting. If not provided, text embeddings will be generated from `prompt` input argument. negative_prompt_embeds (`List[torch.FloatTensor]`, *optional*): Pre-generated negative text embeddings. Can be used to easily tweak text inputs, *e.g.* prompt weighting. If not provided, negative_prompt_embeds will be generated from `negative_prompt` input argument. 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.stable_diffusion.ZImagePipelineOutput`] instead of a plain tuple. joint_attention_kwargs (`dict`, *optional*): A kwargs dictionary that if specified is passed along to the `AttentionProcessor` as defined under `self.processor` in [diffusers.models.attention_processor](https://github.com/huggingface/diffusers/blob/main/src/diffusers/models/attention_processor.py). callback_on_step_end (`Callable`, *optional*): A function that calls at the end of each denoising steps during the inference. The function is called with the following arguments: `callback_on_step_end(self: DiffusionPipeline, step: int, timestep: int, callback_kwargs: Dict)`. `callback_kwargs` will include a list of all tensors as specified by `callback_on_step_end_tensor_inputs`. callback_on_step_end_tensor_inputs (`List`, *optional*): The list of tensor inputs for the `callback_on_step_end` function. The tensors specified in the list will be passed as `callback_kwargs` argument. You will only be able to include variables listed in the `._callback_tensor_inputs` attribute of your pipeline class. max_sequence_length (`int`, *optional*, defaults to 512): Maximum sequence length to use with the `prompt`. Examples: Returns: [`~pipelines.z_image.ZImagePipelineOutput`] or `tuple`: [`~pipelines.z_image.ZImagePipelineOutput`] if `return_dict` is True, otherwise a `tuple`. When returning a tuple, the first element is a list with the generated images. """ height = height or 1024 width = width or 1024 vae_scale = self.vae_scale_factor * 2 if height % vae_scale != 0: raise ValueError( f"Height must be divisible by {vae_scale} (got {height}). " f"Please adjust the height to a multiple of {vae_scale}." ) if width % vae_scale != 0: raise ValueError( f"Width must be divisible by {vae_scale} (got {width}). " f"Please adjust the width to a multiple of {vae_scale}." ) self._guidance_scale = guidance_scale self._joint_attention_kwargs = joint_attention_kwargs self._interrupt = False self._cfg_normalization = cfg_normalization self._cfg_truncation = cfg_truncation # 2. Define call parameters if prompt is not None and isinstance(prompt, str): batch_size = 1 elif prompt is not None and isinstance(prompt, list): batch_size = len(prompt) else: batch_size = len(prompt_embeds) device = self._execution_device weight_dtype = self.text_encoder.dtype num_channels_latents = self.transformer.in_channels if control_image is not None: control_image = self.image_processor.preprocess(control_image, height=height, width=width) control_image = control_image.to(dtype=weight_dtype, device=device) control_latents = self.vae.encode(control_image)[0].mode() control_latents = (control_latents - self.vae.config.shift_factor) * self.vae.config.scaling_factor else: control_latents = torch.zeros_like(inpaint_latent) control_context = control_latents.unsqueeze(2) # If prompt_embeds is provided and prompt is None, skip encoding if prompt_embeds is not None and prompt is None: if self.do_classifier_free_guidance and negative_prompt_embeds is None: raise ValueError( "When `prompt_embeds` is provided without `prompt`, " "`negative_prompt_embeds` must also be provided for classifier-free guidance." ) else: ( prompt_embeds, negative_prompt_embeds, ) = self.encode_prompt( prompt=prompt, negative_prompt=negative_prompt, do_classifier_free_guidance=self.do_classifier_free_guidance, prompt_embeds=prompt_embeds, negative_prompt_embeds=negative_prompt_embeds, device=device, max_sequence_length=max_sequence_length, ) # 4. Prepare latent variables latents = self.prepare_latents( batch_size * num_images_per_prompt, num_channels_latents, height, width, torch.float32, device, generator, latents, ) # Repeat prompt_embeds for num_images_per_prompt if num_images_per_prompt > 1: prompt_embeds = [pe for pe in prompt_embeds for _ in range(num_images_per_prompt)] if self.do_classifier_free_guidance and negative_prompt_embeds: negative_prompt_embeds = [npe for npe in negative_prompt_embeds for _ in range(num_images_per_prompt)] actual_batch_size = batch_size * num_images_per_prompt image_seq_len = (latents.shape[2] // 2) * (latents.shape[3] // 2) # 5. Prepare timesteps mu = calculate_shift( image_seq_len, self.scheduler.config.get("base_image_seq_len", 256), self.scheduler.config.get("max_image_seq_len", 4096), self.scheduler.config.get("base_shift", 0.5), self.scheduler.config.get("max_shift", 1.15), ) self.scheduler.sigma_min = 0.0 scheduler_kwargs = {"mu": mu} timesteps, num_inference_steps = retrieve_timesteps( self.scheduler, num_inference_steps, device, sigmas=sigmas, **scheduler_kwargs, ) num_warmup_steps = max(len(timesteps) - num_inference_steps * self.scheduler.order, 0) self._num_timesteps = len(timesteps) # 6. Denoising loop with self.progress_bar(total=num_inference_steps) as progress_bar: for i, t in enumerate(timesteps): if self.interrupt: continue # broadcast to batch dimension in a way that's compatible with ONNX/Core ML timestep = t.expand(latents.shape[0]) timestep = (1000 - timestep) / 1000 # Normalized time for time-aware config (0 at start, 1 at end) t_norm = timestep[0].item() # Handle cfg truncation current_guidance_scale = self.guidance_scale if ( self.do_classifier_free_guidance and self._cfg_truncation is not None and float(self._cfg_truncation) <= 1 ): if t_norm > self._cfg_truncation: current_guidance_scale = 0.0 # Run CFG only if configured AND scale is non-zero apply_cfg = self.do_classifier_free_guidance and current_guidance_scale > 0 if apply_cfg: latents_typed = latents.to(self.transformer.dtype) latent_model_input = latents_typed.repeat(2, 1, 1, 1) prompt_embeds_model_input = prompt_embeds + negative_prompt_embeds timestep_model_input = timestep.repeat(2) else: latent_model_input = latents.to(self.transformer.dtype) prompt_embeds_model_input = prompt_embeds timestep_model_input = timestep latent_model_input = latent_model_input.unsqueeze(2) latent_model_input_list = list(latent_model_input.unbind(dim=0)) model_out_list = self.transformer( latent_model_input_list, timestep_model_input, prompt_embeds_model_input, control_context=control_context, control_context_scale=control_context_scale, )[0] if apply_cfg: # Perform CFG pos_out = model_out_list[:actual_batch_size] neg_out = model_out_list[actual_batch_size:] noise_pred = [] for j in range(actual_batch_size): pos = pos_out[j].float() neg = neg_out[j].float() pred = pos + current_guidance_scale * (pos - neg) # Renormalization if self._cfg_normalization and float(self._cfg_normalization) > 0.0: ori_pos_norm = torch.linalg.vector_norm(pos) new_pos_norm = torch.linalg.vector_norm(pred) max_new_norm = ori_pos_norm * float(self._cfg_normalization) if new_pos_norm > max_new_norm: pred = pred * (max_new_norm / new_pos_norm) noise_pred.append(pred) noise_pred = torch.stack(noise_pred, dim=0) else: noise_pred = torch.stack([t.float() for t in model_out_list], dim=0) noise_pred = noise_pred.squeeze(2) noise_pred = -noise_pred # compute the previous noisy sample x_t -> x_t-1 latents = self.scheduler.step(noise_pred.to(torch.float32), t, latents, return_dict=False)[0] assert latents.dtype == torch.float32 if callback_on_step_end is not None: callback_kwargs = {} for k in callback_on_step_end_tensor_inputs: callback_kwargs[k] = locals()[k] callback_outputs = callback_on_step_end(self, i, t, callback_kwargs) latents = callback_outputs.pop("latents", latents) prompt_embeds = callback_outputs.pop("prompt_embeds", prompt_embeds) negative_prompt_embeds = callback_outputs.pop("negative_prompt_embeds", negative_prompt_embeds) # call the callback, if provided if i == len(timesteps) - 1 or ((i + 1) > num_warmup_steps and (i + 1) % self.scheduler.order == 0): progress_bar.update() if output_type == "latent": image = latents else: latents = latents.to(self.vae.dtype) latents = (latents / self.vae.config.scaling_factor) + self.vae.config.shift_factor image = self.vae.decode(latents, return_dict=False)[0] image = self.image_processor.postprocess(image, output_type=output_type) # Offload all models self.maybe_free_model_hooks() if not return_dict: return (image,) return ZImagePipelineOutput(images=image)