# Copyright (c) Alibaba Cloud. # # This source code is licensed under the license found in the # LICENSE file in the root directory of this source tree. from collections import OrderedDict import math import requests from io import BytesIO from functools import partial from PIL import Image from typing import Callable, Optional, Sequence, Tuple, List import numpy as np import torch from torch import nn from torch.nn import functional as F from torch.nn.init import trunc_normal_ from torchvision import transforms from torchvision.transforms import InterpolationMode def get_abs_pos(abs_pos, tgt_size): # abs_pos: L, C # tgt_size: M # return: M, C src_size = int(math.sqrt(abs_pos.size(0))) tgt_size = int(math.sqrt(tgt_size)) dtype = abs_pos.dtype if src_size != tgt_size: return F.interpolate( abs_pos.float().reshape(1, src_size, src_size, -1).permute(0, 3, 1, 2), size=(tgt_size, tgt_size), mode="bicubic", align_corners=False, ).permute(0, 2, 3, 1).flatten(0, 2).to(dtype=dtype) else: return abs_pos # https://github.com/facebookresearch/mae/blob/efb2a8062c206524e35e47d04501ed4f544c0ae8/util/pos_embed.py#L20 def get_2d_sincos_pos_embed(embed_dim, grid_size, cls_token=False): """ grid_size: int of the grid height and width return: pos_embed: [grid_size*grid_size, embed_dim] or [1+grid_size*grid_size, embed_dim] (w/ or w/o cls_token) """ grid_h = np.arange(grid_size, dtype=np.float32) grid_w = np.arange(grid_size, dtype=np.float32) grid = np.meshgrid(grid_w, grid_h) # here w goes first grid = np.stack(grid, axis=0) grid = grid.reshape([2, 1, grid_size, grid_size]) pos_embed = get_2d_sincos_pos_embed_from_grid(embed_dim, grid) if cls_token: pos_embed = np.concatenate([np.zeros([1, embed_dim]), pos_embed], axis=0) return pos_embed def get_2d_sincos_pos_embed_from_grid(embed_dim, grid): assert embed_dim % 2 == 0 # use half of dimensions to encode grid_h emb_h = get_1d_sincos_pos_embed_from_grid(embed_dim // 2, grid[0]) # (H*W, D/2) emb_w = get_1d_sincos_pos_embed_from_grid(embed_dim // 2, grid[1]) # (H*W, D/2) emb = np.concatenate([emb_h, emb_w], axis=1) # (H*W, D) return emb def get_1d_sincos_pos_embed_from_grid(embed_dim, pos): """ embed_dim: output dimension for each position pos: a list of positions to be encoded: size (M,) out: (M, D) """ assert embed_dim % 2 == 0 omega = np.arange(embed_dim // 2, dtype=np.float32) omega /= embed_dim / 2. omega = 1. / 10000**omega # (D/2,) pos = pos.reshape(-1) # (M,) out = np.einsum('m,d->md', pos, omega) # (M, D/2), outer product emb_sin = np.sin(out) # (M, D/2) emb_cos = np.cos(out) # (M, D/2) emb = np.concatenate([emb_sin, emb_cos], axis=1) # (M, D) return emb class Resampler(nn.Module): """ A 2D perceiver-resampler network with one cross attention layers by (grid_size**2) learnable queries and 2d sincos pos_emb Outputs: A tensor with the shape of (grid_size**2, embed_dim) """ def __init__( self, grid_size, embed_dim, num_heads, kv_dim=None, norm_layer=nn.LayerNorm ): super().__init__() self.num_queries = grid_size ** 2 self.embed_dim = embed_dim self.num_heads = num_heads self.pos_embed = nn.Parameter( torch.from_numpy(get_2d_sincos_pos_embed(embed_dim, grid_size)).float() ).requires_grad_(False) self.query = nn.Parameter(torch.zeros(self.num_queries, embed_dim)) trunc_normal_(self.query, std=.02) if kv_dim is not None and kv_dim != embed_dim: self.kv_proj = nn.Linear(kv_dim, embed_dim, bias=False) else: self.kv_proj = nn.Identity() self.attn = nn.MultiheadAttention(embed_dim, num_heads) self.ln_q = norm_layer(embed_dim) self.ln_kv = norm_layer(embed_dim) # self.apply(self._init_weights) def _init_weights(self, m): if isinstance(m, nn.Linear): trunc_normal_(m.weight, std=.02) if isinstance(m, nn.Linear) and m.bias is not None: nn.init.constant_(m.bias, 0) elif isinstance(m, nn.LayerNorm): nn.init.constant_(m.bias, 0) nn.init.constant_(m.weight, 1.0) def forward(self, x, attn_mask=None): pos_embed = get_abs_pos(self.pos_embed, x.size(1)) x = self.kv_proj(x) x = self.ln_kv(x).permute(1, 0, 2) N = x.shape[1] q = self.ln_q(self.query) out = self.attn( self._repeat(q, N) + self.pos_embed.unsqueeze(1), x + pos_embed.unsqueeze(1), x, attn_mask=attn_mask)[0] return out.permute(1, 0, 2) def _repeat(self, query, N: int): return query.unsqueeze(1).repeat(1, N, 1) class VisualAttention(nn.Module): """self-attention layer class. Self-attention layer takes input with size [s, b, h] and returns output of the same size. """ def __init__(self, embed_dim, num_heads, bias=True, kdim=None, vdim=None): super(VisualAttention, self).__init__() 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._qkv_same_embed_dim = self.kdim == embed_dim and self.vdim == embed_dim self.num_heads = num_heads # Per attention head and per partition values. assert embed_dim % num_heads == 0 self.hidden_size_per_attention_head = embed_dim // num_heads self.num_attention_heads_per_partition = num_heads self.hidden_size_per_partition = embed_dim # Strided linear layer. assert self._qkv_same_embed_dim, 'Only Support SelfAttention Currently' self.in_proj = nn.Linear(embed_dim, 3 * embed_dim) self.out_proj = nn.Linear(embed_dim, embed_dim) self.norm_factor = math.sqrt(self.hidden_size_per_attention_head) def forward(self, query, key, value, attn_mask = None): # query/key/value: [sq, b, h] sq, b, _ = query.size() assert torch.allclose(query, key), 'Only Support Self-Attention Currently' sk = sq mixed_x_layer = self.in_proj(query) # [sq, b, (np * 3 * hn)] --> [sq, b, np, 3 * hn] new_tensor_shape = mixed_x_layer.size()[:-1] + \ (self.num_attention_heads_per_partition, 3 * self.hidden_size_per_attention_head) mixed_x_layer = mixed_x_layer.view(*new_tensor_shape) # [sq, b, np, 3 * hn] --> 3 [sq, b, np, hn] query_layer, key_layer, value_layer = mixed_x_layer.split( self.hidden_size_per_attention_head, dim=-1) # [sq, b, np, hn] -> [sq, b * np, hn] query_layer = query_layer.view(sq, b * self.num_attention_heads_per_partition, self.hidden_size_per_attention_head).transpose(0, 1) # [sk, b, np, hn] -> [sk, b * np, hn] key_layer = key_layer.view(sk, b * self.num_attention_heads_per_partition, self.hidden_size_per_attention_head).transpose(0, 1) q_scaled = query_layer / self.norm_factor if attn_mask is not None: attention_probs = torch.baddbmm(attn_mask, q_scaled, key_layer.transpose(-2, -1)) else: attention_probs = torch.bmm(q_scaled, key_layer.transpose(-2, -1)) attention_probs = attention_probs.softmax(dim=-1) value_layer = value_layer.view(sk, b * self.num_attention_heads_per_partition, self.hidden_size_per_attention_head).transpose(0, 1) # matmul: [b * np, sq, hn] context_layer = torch.bmm(attention_probs, value_layer) # change view [b, np, sq, hn] context_layer = context_layer.view(b, self.num_attention_heads_per_partition, sq, self.hidden_size_per_attention_head) # [b, np, sq, hn] --> [sq, b, np, hn] context_layer = context_layer.permute(2, 0, 1, 3).contiguous() # [sq, b, np, hn] --> [sq, b, hp] new_context_layer_shape = context_layer.size()[:-2] + \ (self.hidden_size_per_partition,) context_layer = context_layer.view(*new_context_layer_shape) output = self.out_proj(context_layer) return output class VisualAttentionBlock(nn.Module): def __init__( self, d_model: int, n_head: int, mlp_ratio: float = 4.0, act_layer: Callable = nn.GELU, norm_layer: Callable = nn.LayerNorm, is_cross_attention: bool = False, ): super().__init__() self.ln_1 = norm_layer(d_model) if is_cross_attention: self.ln_1_kv = norm_layer(d_model) self.ln_2 = norm_layer(d_model) mlp_width = int(d_model * mlp_ratio) self.attn = VisualAttention(d_model, n_head) self.mlp = nn.Sequential(OrderedDict([ ("c_fc", nn.Linear(d_model, mlp_width)), ("gelu", act_layer()), ("c_proj", nn.Linear(mlp_width, d_model)) ])) def attention( self, q_x: torch.Tensor, k_x: Optional[torch.Tensor] = None, v_x: Optional[torch.Tensor] = None, attn_mask: Optional[torch.Tensor] = None, ): k_x = k_x if k_x is not None else q_x v_x = v_x if v_x is not None else q_x attn_mask = attn_mask.to(q_x.dtype) if attn_mask is not None else None return self.attn(q_x, k_x, v_x, attn_mask=attn_mask) def forward( self, q_x: torch.Tensor, k_x: Optional[torch.Tensor] = None, v_x: Optional[torch.Tensor] = None, attn_mask: Optional[torch.Tensor] = None, ): k_x = self.ln_1_kv(k_x) if hasattr(self, "ln_1_kv") and k_x is not None else None v_x = self.ln_1_kv(v_x) if hasattr(self, "ln_1_kv") and v_x is not None else None x = q_x + self.attention(q_x=self.ln_1(q_x), k_x=k_x, v_x=v_x, attn_mask=attn_mask) x = x + self.mlp(self.ln_2(x)) return x class TransformerBlock(nn.Module): def __init__( self, width: int, layers: int, heads: int, mlp_ratio: float = 4.0, act_layer: Callable = nn.GELU, norm_layer: Callable = nn.LayerNorm, ): super().__init__() self.width = width self.layers = layers self.resblocks = nn.ModuleList([ VisualAttentionBlock( width, heads, mlp_ratio, act_layer=act_layer, norm_layer=norm_layer) for _ in range(layers) ]) def get_cast_dtype(self) -> torch.dtype: return self.resblocks[0].mlp.c_fc.weight.dtype def get_cast_device(self) -> torch.device: return self.resblocks[0].mlp.c_fc.weight.device def forward(self, x: torch.Tensor, attn_mask: Optional[torch.Tensor] = None): for r in self.resblocks: x = r(x, attn_mask=attn_mask) return x class VisionTransformer(nn.Module): def __init__( self, image_size: int, patch_size: int, width: int, layers: int, heads: int, mlp_ratio: float, n_queries: int = 256, output_dim: int = 512, **kwargs ): super().__init__() image_height, image_width = self.image_size = (image_size, image_size) patch_height, patch_width = self.patch_size = (patch_size, patch_size) self.grid_size = (image_height // patch_height, image_width // patch_width) self.output_dim = output_dim mean = (0.48145466, 0.4578275, 0.40821073) std = (0.26862954, 0.26130258, 0.27577711) self.image_transform = transforms.Compose([ transforms.Resize( (image_size, image_size), interpolation=InterpolationMode.BICUBIC ), transforms.ToTensor(), transforms.Normalize(mean=mean, std=std), ]) self.conv1 = nn.Conv2d(in_channels=3, out_channels=width, kernel_size=patch_size, stride=patch_size, bias=False) # class embeddings and positional embeddings scale = width ** -0.5 self.positional_embedding = nn.Parameter(scale * torch.randn(256, width)) norm_layer = partial(nn.LayerNorm, eps=1e-6) act_layer = nn.GELU self.ln_pre = norm_layer(width) self.transformer = TransformerBlock( width, layers, heads, mlp_ratio, act_layer=act_layer, norm_layer=norm_layer, ) self.attn_pool = Resampler( grid_size=int(math.sqrt(n_queries)), embed_dim=output_dim, num_heads=output_dim // 4, kv_dim=width, norm_layer=norm_layer, ) self.ln_post = norm_layer(output_dim) self.proj = nn.Parameter((output_dim** -0.5) * torch.randn(output_dim, output_dim)) def forward(self, x: torch.Tensor): x = x.to( dtype=self.transformer.get_cast_dtype(), device=self.transformer.get_cast_device(), ) # to patches x = self.conv1(x) # shape = [*, width, grid, grid] x = x.reshape(x.shape[0], x.shape[1], -1) # shape = [*, width, grid ** 2] x = x.permute(0, 2, 1) # shape = [*, grid ** 2, width] x = x + get_abs_pos(self.positional_embedding, x.size(1)) x = self.ln_pre(x) x = x.permute(1, 0, 2) # NLD -> LND x = self.transformer(x) x = x.permute(1, 0, 2) # LND -> NLD x = self.attn_pool(x) x = self.ln_post(x) x = x @ self.proj return x def encode(self, image_paths: List[str]): images = [] for image_path in image_paths: if image_path.startswith("http://") or image_path.startswith("https://"): image = Image.open(requests.get(image_path, stream=True).raw) else: image = Image.open(image_path) image = image.convert("RGB") images.append(self.image_transform(image)) images = torch.stack(images, dim=0) return self(images)