ppdiffusers/pipelines/latent_diffusion/pipeline_latent_diffusion.py

# Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
# Copyright 2022 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 Callable, List, Optional, Union

import paddle
import paddle.nn as nn

################################################################################
# Code for the text transformer model
################################################################################
from paddlenlp.transformers import (
    PretrainedModel,
    PretrainedTokenizer,
    register_base_model,
)
from paddlenlp.transformers.model_outputs import (
    BaseModelOutputWithPoolingAndCrossAttentions,
)

from ...configuration_utils import FrozenDict
from ...models import AutoencoderKL, UNet2DConditionModel, UNet2DModel, VQModel
from ...pipeline_utils import DiffusionPipeline, ImagePipelineOutput
from ...schedulers import (
    DDIMScheduler,
    DPMSolverMultistepScheduler,
    EulerAncestralDiscreteScheduler,
    EulerDiscreteScheduler,
    LMSDiscreteScheduler,
    PNDMScheduler,
)
from ...utils import deprecate, logging

logger = logging.get_logger(__name__)  # pylint: disable=invalid-name


class LDMBertPretrainedModel(PretrainedModel):
    pretrained_init_configuration = {}
    pretrained_resource_files_map = {}
    base_model_prefix = "ldmbert"

    def init_weights(self, layer):
        if isinstance(layer, (nn.Linear, nn.Embedding)):
            layer.weight.set_value(
                paddle.normal(
                    mean=0.0,
                    std=self.initializer_range
                    if hasattr(self, "initializer_range")
                    else self.ldmbert.config["initializer_range"],
                    shape=layer.weight.shape,
                )
            )


class LDMBertEmbeddings(nn.Layer):
    def __init__(self, vocab_size, hidden_size=768, hidden_dropout_prob=0.0, max_position_embeddings=512):
        super().__init__()
        self.word_embeddings = nn.Embedding(vocab_size, hidden_size)
        self.position_embeddings = nn.Embedding(max_position_embeddings, hidden_size)
        self.dropout = nn.Dropout(hidden_dropout_prob)

    def forward(self, input_ids, position_ids=None):
        if position_ids is None:
            ones = paddle.ones_like(input_ids, dtype="int64")
            seq_length = paddle.cumsum(ones, axis=-1)
            position_ids = seq_length - ones
            position_ids.stop_gradient = True

        input_embedings = self.word_embeddings(input_ids)
        position_embeddings = self.position_embeddings(position_ids)

        embeddings = input_embedings + position_embeddings
        embeddings = self.dropout(embeddings)
        return embeddings


class TransformerEncoderLayer(nn.TransformerEncoderLayer):
    def __init__(
        self,
        d_model,
        nhead,
        dim_feedforward,
        dropout=0.1,
        activation="gelu",
        attn_dropout=None,
        act_dropout=None,
        normalize_before=False,
        weight_attr=None,
        bias_attr=None,
        head_dim=64,
    ):
        super().__init__(
            d_model,
            nhead,
            dim_feedforward,
            dropout,
            activation,
            attn_dropout,
            act_dropout,
            normalize_before,
            weight_attr,
            bias_attr,
        )
        # update self attn
        self.self_attn = LDMBertAttention(
            d_model, head_dim, nhead, dropout=attn_dropout, weight_attr=weight_attr, bias_attr=False
        )


@register_base_model
class LDMBertModel(LDMBertPretrainedModel):
    _no_split_modules = []

    def __init__(
        self,
        vocab_size=30522,
        max_position_embeddings=77,
        encoder_layers=32,
        encoder_ffn_dim=5120,
        encoder_attention_heads=8,
        head_dim=64,
        activation_function="gelu",
        d_model=1280,
        dropout=0.0,
        attention_dropout=0.0,
        activation_dropout=0.0,
        init_std=0.02,
        pad_token_id=0,
        **kwargs
    ):
        super().__init__()
        self.pad_token_id = pad_token_id
        self.initializer_range = init_std
        self.embeddings = LDMBertEmbeddings(vocab_size, d_model, dropout, max_position_embeddings)
        encoder_layer = TransformerEncoderLayer(
            d_model,
            encoder_attention_heads,
            encoder_ffn_dim,
            dropout=dropout,
            activation=activation_function,
            attn_dropout=attention_dropout,
            act_dropout=activation_dropout,
            normalize_before=True,
            head_dim=head_dim,
        )

        self.encoder = nn.TransformerEncoder(encoder_layer, encoder_layers)
        self.final_layer_norm = nn.LayerNorm(d_model)
        self.apply(self.init_weights)

    def get_input_embeddings(self):
        return self.embeddings.word_embeddings

    def set_input_embeddings(self, value):
        self.embeddings.word_embeddings = value

    def forward(
        self,
        input_ids,
        position_ids=None,
        attention_mask=None,
        output_hidden_states=False,
        output_attentions=False,
        return_dict=False,
    ):

        if attention_mask is not None and attention_mask.ndim == 2:
            # attention_mask [batch_size, sequence_length] -> [batch_size, 1, 1, sequence_length]
            attention_mask = attention_mask.unsqueeze(axis=[1, 2]).astype(paddle.get_default_dtype())
            attention_mask = (1.0 - attention_mask) * -1e4

        embedding_output = self.embeddings(input_ids=input_ids, position_ids=position_ids)

        encoder_outputs = self.encoder(
            embedding_output,
            src_mask=attention_mask,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )

        if isinstance(encoder_outputs, type(embedding_output)):
            sequence_output = self.final_layer_norm(encoder_outputs)
            return (sequence_output,)
        else:
            sequence_output = encoder_outputs[0]
            sequence_output = self.final_layer_norm(sequence_output)
            if not return_dict:
                return (sequence_output,) + encoder_outputs[1:]
            return BaseModelOutputWithPoolingAndCrossAttentions(
                last_hidden_state=sequence_output,
                hidden_states=encoder_outputs.hidden_states,
                attentions=encoder_outputs.attentions,
            )


class LDMBertAttention(nn.MultiHeadAttention):
    def __init__(
        self,
        embed_dim,
        head_dim,
        num_heads,
        dropout=0.0,
        kdim=None,
        vdim=None,
        need_weights=False,
        weight_attr=None,
        bias_attr=None,
    ):
        super().__init__(embed_dim, num_heads, dropout, kdim, vdim, need_weights, weight_attr, bias_attr)
        assert embed_dim > 0, "Expected embed_dim to be greater than 0, " "but recieved {}".format(embed_dim)
        assert num_heads > 0, "Expected num_heads to be greater than 0, " "but recieved {}".format(num_heads)

        self.embed_dim = embed_dim
        self.kdim = kdim if kdim is not None else embed_dim
        self.vdim = vdim if vdim is not None else embed_dim
        self.num_heads = num_heads
        self.dropout = dropout
        self.need_weights = need_weights

        self.head_dim = head_dim
        self.inner_dim = head_dim * num_heads
        self.scaling = self.head_dim**-0.5

        self.q_proj = nn.Linear(embed_dim, self.inner_dim, weight_attr, bias_attr=bias_attr)
        self.k_proj = nn.Linear(self.kdim, self.inner_dim, weight_attr, bias_attr=bias_attr)
        self.v_proj = nn.Linear(self.vdim, self.inner_dim, weight_attr, bias_attr=bias_attr)
        self.out_proj = nn.Linear(self.inner_dim, embed_dim, weight_attr)


class LDMBertModelForMaskedLM(LDMBertPretrainedModel):
    def __init__(self, ldmbert):
        super().__init__()
        self.ldmbert = ldmbert
        self.to_logits = nn.Linear(ldmbert.config["hidden_size"], ldmbert.config["vocab_size"])
        self.apply(self.init_weights)

    def forward(
        self,
        input_ids=None,
        attention_mask=None,
        position_ids=None,
        output_attentions=None,
        output_hidden_states=None,
        return_dict=None,
    ):
        outputs = self.ldmbert(
            input_ids,
            attention_mask=attention_mask,
            position_ids=position_ids,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )
        return outputs


class LDMTextToImagePipeline(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 xxxx, etc.)

    Parameters:
        vqvae ([`VQModel`]):
            Vector-quantized (VQ) Model to encode and decode images to and from latent representations.
        bert ([`LDMBertModel`]):
            Text-encoder model based on [BERT](https://paddlenlp.readthedocs.io/zh/latest/source/paddlenlp.transformers.bert.modeling.html#paddlenlp.transformers.bert.modeling.BertModel) architecture.
        tokenizer (`paddlenlp.transformers.BertTokenizer`):
            Tokenizer of class
            [BertTokenizer](https://paddlenlp.readthedocs.io/zh/latest/source/paddlenlp.transformers.bert.tokenizer.html#paddlenlp.transformers.bert.tokenizer.BertTokenizer).
        unet ([`UNet2DConditionModel`]): Conditional U-Net architecture to denoise the encoded image latents.
        scheduler ([`SchedulerMixin`]):
            A scheduler to be used in combination with `unet` to denoise the encoded image latents. Can be one of
            [`DDIMScheduler`], [`LMSDiscreteScheduler`], [`PNDMScheduler`], [`EulerDiscreteScheduler`], [`EulerAncestralDiscreteScheduler`]
            or [`DPMSolverMultistepScheduler`].
    """

    def __init__(
        self,
        vqvae: Union[VQModel, AutoencoderKL],
        bert: PretrainedModel,
        tokenizer: PretrainedTokenizer,
        unet: Union[UNet2DModel, UNet2DConditionModel],
        scheduler: Union[
            DDIMScheduler,
            PNDMScheduler,
            LMSDiscreteScheduler,
            EulerDiscreteScheduler,
            EulerAncestralDiscreteScheduler,
            DPMSolverMultistepScheduler,
        ],
    ):
        super().__init__()
        if hasattr(scheduler.config, "steps_offset") and scheduler.config.steps_offset != 1:
            deprecation_message = (
                f"The configuration file of this scheduler: {scheduler} is outdated. `steps_offset`"
                f" should be set to 1 instead of {scheduler.config.steps_offset}. Please make sure "
                "to update the config accordingly as leaving `steps_offset` might led to incorrect results"
                " in future versions. If you have downloaded this checkpoint from the Hugging Face Hub,"
                " it would be very nice if you could open a Pull request for the `scheduler/scheduler_config.json`"
                " file"
            )
            deprecate("steps_offset!=1", "1.0.0", deprecation_message, standard_warn=False)
            new_config = dict(scheduler.config)
            new_config["steps_offset"] = 1
            scheduler._internal_dict = FrozenDict(new_config)

        if hasattr(scheduler.config, "clip_sample") and scheduler.config.clip_sample is True:
            deprecation_message = (
                f"The configuration file of this scheduler: {scheduler} has not set the configuration `clip_sample`."
                " `clip_sample` should be set to False in the configuration file. Please make sure to update the"
                " config accordingly as not setting `clip_sample` in the config might lead to incorrect results in"
                " future versions. If you have downloaded this checkpoint from the Hugging Face Hub, it would be very"
                " nice if you could open a Pull request for the `scheduler/scheduler_config.json` file"
            )
            deprecate("clip_sample not set", "1.0.0", deprecation_message, standard_warn=False)
            new_config = dict(scheduler.config)
            new_config["clip_sample"] = False
            scheduler._internal_dict = FrozenDict(new_config)

        self.register_modules(vqvae=vqvae, bert=bert, tokenizer=tokenizer, unet=unet, scheduler=scheduler)
        self.vae_scale_factor = 2 ** (len(self.vqvae.config.block_out_channels) - 1)

    def _encode_prompt(self, prompt, num_images_per_prompt, do_classifier_free_guidance, negative_prompt):
        r"""
        Encodes the prompt into text encoder hidden states.

        Args:
            prompt (`str` or `list(int)`):
                prompt to be encoded
            num_images_per_prompt (`int`):
                number of images that should be generated per prompt
            do_classifier_free_guidance (`bool`):
                whether to use classifier free guidance or not
            negative_prompt (`str` or `List[str]`):
                The prompt or prompts not to guide the image generation. Ignored when not using guidance (i.e., ignored
                if `guidance_scale` is less than `1`).
        """
        batch_size = len(prompt) if isinstance(prompt, list) else 1

        text_inputs = self.tokenizer(
            prompt,
            padding="max_length",
            max_length=self.tokenizer.model_max_length,
            truncation=True,
            return_tensors="pd",
        )
        text_input_ids = text_inputs.input_ids
        untruncated_ids = self.tokenizer(prompt, padding="longest", return_tensors="pd").input_ids

        if untruncated_ids.shape[-1] >= text_input_ids.shape[-1] and not paddle.equal_all(
            text_input_ids, untruncated_ids
        ):
            removed_text = self.tokenizer.batch_decode(untruncated_ids[:, self.tokenizer.model_max_length - 1 : -1])
            logger.warning(
                "The following part of your input was truncated because LDMBert can only handle sequences up to"
                f" {self.tokenizer.model_max_length} tokens: {removed_text}"
            )

        text_embeddings = self.bert(text_input_ids)
        text_embeddings = text_embeddings[0]

        # duplicate text embeddings for each generation per prompt, using mps friendly method
        bs_embed, seq_len, _ = text_embeddings.shape
        text_embeddings = text_embeddings.tile([1, num_images_per_prompt, 1])
        text_embeddings = text_embeddings.reshape([bs_embed * num_images_per_prompt, seq_len, -1])

        # get unconditional embeddings for classifier free guidance
        if do_classifier_free_guidance:
            uncond_tokens: List[str]
            if negative_prompt is None:
                uncond_tokens = [""] * batch_size
            elif type(prompt) is not type(negative_prompt):
                raise TypeError(
                    f"`negative_prompt` should be the same type to `prompt`, but got {type(negative_prompt)} !="
                    f" {type(prompt)}."
                )
            elif isinstance(negative_prompt, str):
                uncond_tokens = [negative_prompt]
            elif batch_size != len(negative_prompt):
                raise ValueError(
                    f"`negative_prompt`: {negative_prompt} has batch size {len(negative_prompt)}, but `prompt`:"
                    f" {prompt} has batch size {batch_size}. Please make sure that passed `negative_prompt` matches"
                    " the batch size of `prompt`."
                )
            else:
                uncond_tokens = negative_prompt

            max_length = text_input_ids.shape[-1]
            uncond_input = self.tokenizer(
                uncond_tokens,
                padding="max_length",
                max_length=max_length,
                truncation=True,
                return_tensors="pd",
            )

            uncond_embeddings = self.bert(uncond_input.input_ids)
            uncond_embeddings = uncond_embeddings[0]

            # duplicate unconditional embeddings for each generation per prompt, using mps friendly method
            seq_len = uncond_embeddings.shape[1]
            uncond_embeddings = uncond_embeddings.tile([1, num_images_per_prompt, 1])
            uncond_embeddings = uncond_embeddings.reshape([batch_size * num_images_per_prompt, seq_len, -1])

            # For classifier free guidance, we need to do two forward passes.
            # Here we concatenate the unconditional and text embeddings into a single batch
            # to avoid doing two forward passes
            text_embeddings = paddle.concat([uncond_embeddings, text_embeddings])

        return text_embeddings

    def decode_latents(self, latents):
        latents = 1 / 0.18215 * latents
        image = self.vqvae.decode(latents).sample
        image = (image / 2 + 0.5).clip(0, 1)
        # we always cast to float32 as this does not cause significant overhead and is compatible with bfloa16
        image = image.transpose([0, 2, 3, 1]).cast("float32").numpy()
        return image

    def prepare_extra_step_kwargs(self, generator, eta):
        # prepare extra kwargs for the scheduler step, since not all schedulers have the same signature
        # eta (η) is only used with the DDIMScheduler, it will be ignored for other schedulers.
        # eta corresponds to η in DDIM paper: https://arxiv.org/abs/2010.02502
        # and should be between [0, 1]

        accepts_eta = "eta" in set(inspect.signature(self.scheduler.step).parameters.keys())
        extra_step_kwargs = {}
        if accepts_eta:
            extra_step_kwargs["eta"] = eta

        # check if the scheduler accepts generator
        accepts_generator = "generator" in set(inspect.signature(self.scheduler.step).parameters.keys())
        if accepts_generator:
            extra_step_kwargs["generator"] = generator
        return extra_step_kwargs

    def check_inputs(self, prompt, height, width, callback_steps):
        if not isinstance(prompt, str) and not isinstance(prompt, list):
            raise ValueError(f"`prompt` has to be of type `str` or `list` but is {type(prompt)}")

        if height % 8 != 0 or width % 8 != 0:
            raise ValueError(f"`height` and `width` have to be divisible by 8 but are {height} and {width}.")

        if (callback_steps is None) or (
            callback_steps is not None and (not isinstance(callback_steps, int) or callback_steps <= 0)
        ):
            raise ValueError(
                f"`callback_steps` has to be a positive integer but is {callback_steps} of type"
                f" {type(callback_steps)}."
            )

    def prepare_latents(self, batch_size, num_channels_latents, height, width, dtype, generator, latents=None):
        shape = [batch_size, num_channels_latents, height // self.vae_scale_factor, width // self.vae_scale_factor]
        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."
            )

        if latents is None:
            if isinstance(generator, list):
                shape = [
                    1,
                ] + shape[1:]
                latents = [paddle.randn(shape, generator=generator[i], dtype=dtype) for i in range(batch_size)]
                latents = paddle.concat(latents, axis=0)
            else:
                latents = paddle.randn(shape, generator=generator, dtype=dtype)
        else:
            if latents.shape != shape:
                raise ValueError(f"Unexpected latents shape, got {latents.shape}, expected {shape}")

        # scale the initial noise by the standard deviation required by the scheduler
        latents = latents * self.scheduler.init_noise_sigma
        return latents

    @paddle.no_grad()
    def __call__(
        self,
        prompt: Union[str, List[str]],
        height: int = 256,
        width: int = 256,
        num_inference_steps: int = 50,
        guidance_scale: float = 1.0,
        negative_prompt: Optional[Union[str, List[str]]] = None,
        num_images_per_prompt: Optional[int] = 1,
        eta: float = 0.0,
        generator: Optional[Union[paddle.Generator, List[paddle.Generator]]] = None,
        latents: Optional[paddle.Tensor] = None,
        output_type: Optional[str] = "pil",
        return_dict: bool = True,
        callback: Optional[Callable[[int, int, paddle.Tensor], None]] = None,
        callback_steps: Optional[int] = 1,
    ):
        r"""
        Function invoked when calling the pipeline for generation.

        Args:
            prompt (`str` or `List[str]`):
                The prompt or prompts to guide the image generation.
            height (`int`, *optional*, defaults to 256:
                The height in pixels of the generated image.
            width (`int`, *optional*, defaults to 256:
                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.
            guidance_scale (`float`, *optional*, defaults to 1.0):
                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.
            negative_prompt (`str` or `List[str]`, *optional*):
                The prompt or prompts not to guide the image generation. 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.
            eta (`float`, *optional*, defaults to 0.0):
                Corresponds to parameter eta (η) in the DDIM paper: https://arxiv.org/abs/2010.02502. Only applies to
                [`schedulers.DDIMScheduler`], will be ignored for others.
            generator (`paddle.Generator`, *optional*):
                One or a list of paddle generator(s) to make generation deterministic.
            latents (`paddle.Tensor`, *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 ge generated by sampling using the supplied random `generator`.
            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.StableDiffusionPipelineOutput`] instead of a
                plain tuple.
            callback (`Callable`, *optional*):
                A function that will be called every `callback_steps` steps during inference. The function will be
                called with the following arguments: `callback(step: int, timestep: int, latents: paddle.Tensor)`.
            callback_steps (`int`, *optional*, defaults to 1):
                The frequency at which the `callback` function will be called. If not specified, the callback will be
                called at every step.

        Returns:
            [`~pipelines.stable_diffusion.StableDiffusionPipelineOutput`] or `tuple`:
            [`~pipelines.stable_diffusion.StableDiffusionPipelineOutput`] if `return_dict` is True, otherwise a `tuple.
            When returning a tuple, the first element is a list with the generated images, and the second element is a
            list of `bool`s denoting whether the corresponding generated image likely represents "not-safe-for-work"
            (nsfw) content, according to the `safety_checker`.
        """
        # 1. Check inputs. Raise error if not correct
        self.check_inputs(prompt, height, width, callback_steps)

        # 2. Define call parameters
        batch_size = 1 if isinstance(prompt, str) else len(prompt)
        # here `guidance_scale` is defined analog to the guidance weight `w` of equation (2)
        # of the Imagen paper: https://arxiv.org/pdf/2205.11487.pdf . `guidance_scale = 1`
        # corresponds to doing no classifier free guidance.
        do_classifier_free_guidance = guidance_scale > 1.0

        # 3. Encode input prompt
        text_embeddings = self._encode_prompt(
            prompt, num_images_per_prompt, do_classifier_free_guidance, negative_prompt
        )

        # 4. Prepare timesteps
        self.scheduler.set_timesteps(num_inference_steps)
        timesteps = self.scheduler.timesteps

        # 5. Prepare latent variables
        num_channels_latents = self.unet.in_channels
        latents = self.prepare_latents(
            batch_size * num_images_per_prompt,
            num_channels_latents,
            height,
            width,
            text_embeddings.dtype,
            generator,
            latents,
        )

        # 6. Prepare extra step kwargs. TODO: Logic should ideally just be moved out of the pipeline
        extra_step_kwargs = self.prepare_extra_step_kwargs(generator, eta)

        # 7. Denoising loop
        num_warmup_steps = len(timesteps) - num_inference_steps * self.scheduler.order
        with self.progress_bar(total=num_inference_steps) as progress_bar:
            for i, t in enumerate(timesteps):
                # expand the latents if we are doing classifier free guidance
                latent_model_input = paddle.concat([latents] * 2) if do_classifier_free_guidance else latents
                latent_model_input = self.scheduler.scale_model_input(latent_model_input, t)

                # predict the noise residual
                noise_pred = self.unet(latent_model_input, t, encoder_hidden_states=text_embeddings).sample

                # perform guidance
                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)

                # compute the previous noisy sample x_t -> x_t-1
                latents = self.scheduler.step(noise_pred, t, latents, **extra_step_kwargs).prev_sample

                # 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 callback is not None and i % callback_steps == 0:
                        callback(i, t, latents)

        # 8. Post-processing
        image = self.decode_latents(latents)

        # 9. Convert to PIL
        if output_type == "pil":
            image = self.numpy_to_pil(image)

        if not return_dict:
            return (image,)

        return ImagePipelineOutput(images=image)