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import torch
from torch import nn
from einops import rearrange, repeat
from einops.layers.torch import Rearrange
# helpers
def pair(t):
return t if isinstance(t, tuple) else (t, t)
# classes
class FeedForward(nn.Module):
def __init__(self, dim, hidden_dim, dropout = 0.):
super().__init__()
self.net = nn.Sequential(
nn.LayerNorm(dim),
nn.Linear(dim, hidden_dim),
nn.GELU(),
nn.Dropout(dropout),
nn.Linear(hidden_dim, dim),
nn.Dropout(dropout)
)
def forward(self, x):
return self.net(x)
class Attention(nn.Module):
def __init__(self, dim, heads = 8, dim_head = 64, dropout = 0.):
super().__init__()
inner_dim = dim_head * heads
project_out = not (heads == 1 and dim_head == dim)
self.heads = heads
self.scale = dim_head ** -0.5
self.norm = nn.LayerNorm(dim)
self.attend = nn.Softmax(dim = -1)
self.dropout = nn.Dropout(dropout)
self.to_qkv = nn.Linear(dim, inner_dim * 3, bias = False)
self.to_out = nn.Sequential(
nn.Linear(inner_dim, dim),
nn.Dropout(dropout)
) if project_out else nn.Identity()
def forward(self, x):
x = self.norm(x)
qkv = self.to_qkv(x).chunk(3, dim = -1)
q, k, v = map(lambda t: rearrange(t, 'b n (h d) -> b h n d', h = self.heads), qkv)
dots = torch.matmul(q, k.transpose(-1, -2)) * self.scale
attn = self.attend(dots)
attn = self.dropout(attn)
out = torch.matmul(attn, v)
out = rearrange(out, 'b h n d -> b n (h d)')
return self.to_out(out)
class Transformer(nn.Module):
def __init__(self, dim, depth, heads, dim_head, mlp_dim, dropout = 0.):
super().__init__()
self.norm = nn.LayerNorm(dim)
self.layers = nn.ModuleList([])
for _ in range(depth):
self.layers.append(nn.ModuleList([
Attention(dim, heads = heads, dim_head = dim_head, dropout = dropout),
FeedForward(dim, mlp_dim, dropout = dropout)
]))
def forward(self, x):
for attn, ff in self.layers:
x = attn(x) + x
x = ff(x) + x
return self.norm(x)
class ViTEncoder(nn.Module):
def __init__(self, *, image_size, patch_size, dim, depth, heads, mlp_dim, pool = 'cls', channels = 3, dim_head = 64, dropout = 0., emb_dropout = 0.):
super().__init__()
image_height, image_width = pair(image_size)
patch_height, patch_width = pair(patch_size)
assert image_height % patch_height == 0 and image_width % patch_width == 0, 'Image dimensions must be divisible by the patch size.'
num_patches = (image_height // patch_height) * (image_width // patch_width)
patch_dim = channels * patch_height * patch_width
assert pool in {'cls', 'mean'}, 'pool type must be either cls (cls token) or mean (mean pooling)'
self.to_patch_embedding = nn.Sequential(
Rearrange('b c (h p1) (w p2) -> b (h w) (p1 p2 c)', p1 = patch_height, p2 = patch_width),
nn.LayerNorm(patch_dim),
nn.Linear(patch_dim, dim),
nn.LayerNorm(dim),
)
self.pos_embedding = nn.Parameter(torch.randn(1, num_patches + 1, dim))
self.cls_token = nn.Parameter(torch.randn(1, 1, dim))
self.dropout = nn.Dropout(emb_dropout)
self.transformer = Transformer(dim, depth, heads, dim_head, mlp_dim, dropout)
self.pool = pool
self.to_latent = nn.Identity()
def forward(self, img):
x = self.to_patch_embedding(img)
b, n, _ = x.shape
cls_tokens = repeat(self.cls_token, '1 1 d -> b 1 d', b = b)
x = torch.cat((cls_tokens, x), dim=1)
x += self.pos_embedding[:, :(n + 1)]
x = self.dropout(x)
x = self.transformer(x)
x = x.mean(dim = 1) if self.pool == 'mean' else x[:, 0]
x = self.to_latent(x)
x = x.view(x.size(0), -1, 1, 1)
return x
class ViTDecoder(nn.Module):
def __init__(self, *, image_size, patch_size, dim, depth, heads, mlp_dim, pool = 'cls', channels = 3, dim_head = 64, dropout = 0., emb_dropout = 0.):
super().__init__()
image_height, image_width = pair(image_size)
patch_height, patch_width = pair(patch_size)
assert image_height % patch_height == 0 and image_width % patch_width == 0, 'Image dimensions must be divisible by the patch size.'
self.num_patches = (image_height // patch_height) * (image_width // patch_width)
pixel_values_per_patch = patch_height * patch_width * 3
self.decoder_dim = dim
self.mask_token = nn.Parameter(torch.randn(dim))
self.decoder = Transformer(dim, depth, heads, dim_head, mlp_dim, dropout)
self.pos_embedding = nn.Parameter(torch.randn(1, self.num_patches + 1, dim))
self.to_pixels = nn.Linear(dim, pixel_values_per_patch)
self.dropout = nn.Dropout(emb_dropout)
self.token2_image = Rearrange('b (h w) (p1 p2 c) -> b c (h p1) (w p2)', p1 = patch_height, p2 = patch_width, h=image_height//patch_height, w=image_width//patch_width)
def forward(self, latent):
batch = latent.size(0)
device = latent.device
latent = latent.view(batch, -1)
decoder_tokens = torch.zeros(batch, self.num_patches+1, self.decoder_dim, device=device)
decoder_tokens[:, 0] = latent
mask_tokens = repeat(self.mask_token, 'd -> b n d', b = batch, n = self.num_patches)
decoder_tokens[:, 1:] = mask_tokens
decoder_tokens += self.pos_embedding
decoder_tokens = self.dropout(decoder_tokens)
decoded_tokens = self.decoder(decoder_tokens)
# splice out the mask tokens and project to pixel values
mask_tokens = decoded_tokens[:, 1:]
pred_pixel_values = self.to_pixels(mask_tokens)
pred_image = self.token2_image(pred_pixel_values)
return pred_image
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