sd_samplers.py

from collections import namedtuple
import torch
import tqdm

import k_diffusion.sampling
from ldm.models.diffusion.ddim import DDIMSampler
from ldm.models.diffusion.plms import PLMSSampler

from modules.shared import opts, cmd_opts, state
import modules.shared as shared

SamplerData = namedtuple('SamplerData', ['name', 'constructor'])
samplers = [
    *[SamplerData(x[0], lambda model, funcname=x[1]: KDiffusionSampler(funcname, model)) for x in [
        ('Euler a', 'sample_euler_ancestral'),
        ('Euler', 'sample_euler'),
        ('LMS', 'sample_lms'),
        ('Heun', 'sample_heun'),
        ('DPM2', 'sample_dpm_2'),
        ('DPM2 a', 'sample_dpm_2_ancestral'),
    ] if hasattr(k_diffusion.sampling, x[1])],
    SamplerData('DDIM', lambda model: VanillaStableDiffusionSampler(DDIMSample, model)),
    SamplerData('PLMS', lambda model: VanillaStableDiffusionSampler(PLMSSampler, model)),
]
samplers_for_img2img = [x for x in samplers if x.name != 'PLMS']


def p_sample_ddim_hook(sampler_wrapper, x_dec, cond, ts, *args, **kwargs):
    if sampler_wrapper.mask is not None:
        img_orig = sampler_wrapper.sampler.model.q_sample(sampler_wrapper.init_latent, ts)
        x_dec = img_orig * sampler_wrapper.mask + sampler_wrapper.nmask * x_dec

    return sampler_wrapper.orig_p_sample_ddim(x_dec, cond, ts, *args, **kwargs)


class VanillaStableDiffusionSampler:
    def __init__(self, constructor, sd_model):
        self.sampler = constructor(sd_model)
        self.orig_p_sample_ddim = self.sampler.p_sample_ddim if hasattr(self.sampler, 'p_sample_ddim') else None
        self.mask = None
        self.nmask = None
        self.init_latent = None

    def sample_img2img(self, p, x, noise, conditioning, unconditional_conditioning):
        t_enc = int(min(p.denoising_strength, 0.999) * p.steps)

        # existing code fails with cetin step counts, like 9
        try:
            self.sampler.make_schedule(ddim_num_steps=p.steps, verbose=False)
        except Exception:
            self.sampler.make_schedule(ddim_num_steps=p.steps+1, verbose=False)

        x1 = self.sampler.stochastic_encode(x, torch.tensor([t_enc] * int(x.shape[0])).to(shared.device), noise=noise)

        self.sampler.p_sample_ddim = lambda x_dec, cond, ts, *args, **kwargs: p_sample_ddim_hook(self, x_dec, cond, ts, *args, **kwargs)
        self.mask = p.mask
        self.nmask = p.nmask
        self.init_latent = p.init_latent

        samples = self.sampler.decode(x1, conditioning, t_enc, unconditional_guidance_scale=p.cfg_scale, unconditional_conditioning=unconditional_conditioning)

        return samples

    def sample(self, p, x, conditioning, unconditional_conditioning):
        samples_ddim, _ = self.sampler.sample(S=p.steps, conditioning=conditioning, batch_size=int(x.shape[0]), shape=x[0].shape, verbose=False, unconditional_guidance_scale=p.cfg_scale, unconditional_conditioning=unconditional_conditioning, x_T=x)
        return samples_ddim


class CFGDenoiser(torch.nn.Module):
    def __init__(self, model):
        super().__init__()
        self.inner_model = model
        self.mask = None
        self.nmask = None
        self.init_latent = None

    def forward(self, x, sigma, uncond, cond, cond_scale):
        if shared.batch_cond_uncond:
            x_in = torch.cat([x] * 2)
            sigma_in = torch.cat([sigma] * 2)
            cond_in = torch.cat([uncond, cond])
            uncond, cond = self.inner_model(x_in, sigma_in, cond=cond_in).chunk(2)
            denoised = uncond + (cond - uncond) * cond_scale
        else:
            uncond = self.inner_model(x, sigma, cond=uncond)
            cond = self.inner_model(x, sigma, cond=cond)
            denoised = uncond + (cond - uncond) * cond_scale

        if self.mask is not None:
            denoised = self.init_latent * self.mask + self.nmask * denoised

        return denoised


def extended_trange(*args, **kwargs):
    for x in tqdm.trange(*args, desc=state.job, **kwargs):
        if state.interrupted:
            break

        yield x


class KDiffusionSampler:
    def __init__(self, funcname, sd_model):
        self.model_wrap = k_diffusion.external.CompVisDenoiser(sd_model)
        self.funcname = funcname
        self.func = getattr(k_diffusion.sampling, self.funcname)
        self.model_wrap_cfg = CFGDenoiser(self.model_wrap)

    def sample_img2img(self, p, x, noise, conditioning, unconditional_conditioning):
        t_enc = int(min(p.denoising_strength, 0.999) * p.steps)
        sigmas = self.model_wrap.get_sigmas(p.steps)
        noise = noise * sigmas[p.steps - t_enc - 1]

        xi = x + noise

        sigma_sched = sigmas[p.steps - t_enc - 1:]

        self.model_wrap_cfg.mask = p.mask
        self.model_wrap_cfg.nmask = p.nmask
        self.model_wrap_cfg.init_latent = p.init_latent

        if hasattr(k_diffusion.sampling, 'trange'):
            k_diffusion.sampling.trange = lambda *args, **kwargs: extended_trange(*args, **kwargs)

        return self.func(self.model_wrap_cfg, xi, sigma_sched, extra_args={'cond': conditioning, 'uncond': unconditional_conditioning, 'cond_scale': p.cfg_scale}, disable=False)

    def sample(self, p, x, conditioning, unconditional_conditioning):
        sigmas = self.model_wrap.get_sigmas(p.steps)
        x = x * sigmas[0]

        if hasattr(k_diffusion.sampling, 'trange'):
            k_diffusion.sampling.trange = lambda *args, **kwargs: extended_trange(*args, **kwargs)

        samples_ddim = self.func(self.model_wrap_cfg, x, sigmas, extra_args={'cond': conditioning, 'uncond': unconditional_conditioning, 'cond_scale': p.cfg_scale}, disable=False)
        return samples_ddim