""" Image to Patch Embedding using Conv2d
A convolution based approach to patchifying a 2D image w/ embedding projection.
Based on code in:
* https://github.com/google-research/vision_transformer
* https://github.com/google-research/big_vision/tree/main/big_vision
Hacked together by / Copyright 2020 Ross Wightman
"""
import logging
from typing import List, Optional, Callable
import torch
from torch import nn as nn
import torch.nn.functional as F
from .format import Format, nchw_to
from .helpers import to_2tuple
from .trace_utils import _assert
_logger = logging.getLogger(__name__)
class PatchEmbed(nn.Module):
""" 2D Image to Patch Embedding
"""
output_fmt: Format
def __init__(
self,
img_size: int = 224,
patch_size: int = 16,
in_chans: int = 3,
embed_dim: int = 768,
norm_layer: Optional[Callable] = None,
flatten: bool = True,
output_fmt: Optional[str] = None,
bias: bool = True,
):
super().__init__()
img_size = to_2tuple(img_size)
patch_size = to_2tuple(patch_size)
self.img_size = img_size
self.patch_size = patch_size
self.grid_size = (img_size[0] // patch_size[0], img_size[1] // patch_size[1])
self.num_patches = self.grid_size[0] * self.grid_size[1]
if output_fmt is not None:
self.flatten = False
self.output_fmt = Format(output_fmt)
else:
# flatten spatial dim and transpose to channels last, kept for bwd compat
self.flatten = flatten
self.output_fmt = Format.NCHW
self.proj = nn.Conv2d(in_chans, embed_dim, kernel_size=patch_size, stride=patch_size, bias=bias)
self.norm = norm_layer(embed_dim) if norm_layer else nn.Identity()
def forward(self, x):
B, C, H, W = x.shape
_assert(H == self.img_size[0], f"Input image height ({H}) doesn't match model ({self.img_size[0]}).")
_assert(W == self.img_size[1], f"Input image width ({W}) doesn't match model ({self.img_size[1]}).")
x = self.proj(x)
if self.flatten:
x = x.flatten(2).transpose(1, 2) # NCHW -> NLC
elif self.output_fmt != Format.NCHW:
x = nchw_to(x, self.output_fmt)
x = self.norm(x)
return x
def resample_patch_embed(
patch_embed,
new_size: List[int],
interpolation: str = 'bicubic',
antialias: bool = True,
verbose: bool = False,
):
"""Resample the weights of the patch embedding kernel to target resolution.
We resample the patch embedding kernel by approximately inverting the effect
of patch resizing.
Code based on:
https://github.com/google-research/big_vision/blob/b00544b81f8694488d5f36295aeb7972f3755ffe/big_vision/models/proj/flexi/vit.py
With this resizing, we can for example load a B/8 filter into a B/16 model
and, on 2x larger input image, the result will match.
Args:
patch_embed: original parameter to be resized.
new_size (tuple(int, int): target shape (height, width)-only.
interpolation (str): interpolation for resize
antialias (bool): use anti-aliasing filter in resize
verbose (bool): log operation
Returns:
Resized patch embedding kernel.
"""
import numpy as np
try:
import functorch
vmap = functorch.vmap
except ImportError:
if hasattr(torch, 'vmap'):
vmap = torch.vmap
else:
assert False, "functorch or a version of torch with vmap is required for FlexiViT resizing."
assert len(patch_embed.shape) == 4, "Four dimensions expected"
assert len(new_size) == 2, "New shape should only be hw"
old_size = patch_embed.shape[-2:]
if tuple(old_size) == tuple(new_size):
return patch_embed
if verbose:
_logger.info(f"Resize patch embedding {patch_embed.shape} to {new_size}, w/ {interpolation} interpolation.")
def resize(x_np, _new_size):
x_tf = torch.Tensor(x_np)[None, None, ...]
x_upsampled = F.interpolate(
x_tf, size=_new_size, mode=interpolation, antialias=antialias)[0, 0, ...].numpy()
return x_upsampled
def get_resize_mat(_old_size, _new_size):
mat = []
for i in range(np.prod(_old_size)):
basis_vec = np.zeros(_old_size)
basis_vec[np.unravel_index(i, _old_size)] = 1.
mat.append(resize(basis_vec, _new_size).reshape(-1))
return np.stack(mat).T
resize_mat = get_resize_mat(old_size, new_size)
resize_mat_pinv = torch.Tensor(np.linalg.pinv(resize_mat.T))
def resample_kernel(kernel):
resampled_kernel = resize_mat_pinv @ kernel.reshape(-1)
return resampled_kernel.reshape(new_size)
v_resample_kernel = vmap(vmap(resample_kernel, 0, 0), 1, 1)
return v_resample_kernel(patch_embed)
# def divs(n, m=None):
# m = m or n // 2
# if m == 1:
# return [1]
# if n % m == 0:
# return [m] + divs(n, m - 1)
# return divs(n, m - 1)
#
#
# class FlexiPatchEmbed(nn.Module):
# """ 2D Image to Patch Embedding w/ Flexible Patch sizes (FlexiViT)
# FIXME WIP
# """
# def __init__(
# self,
# img_size=240,
# patch_size=16,
# in_chans=3,
# embed_dim=768,
# base_img_size=240,
# base_patch_size=32,
# norm_layer=None,
# flatten=True,
# bias=True,
# ):
# super().__init__()
# self.img_size = to_2tuple(img_size)
# self.patch_size = to_2tuple(patch_size)
# self.num_patches = 0
#
# # full range for 240 = (5, 6, 8, 10, 12, 14, 15, 16, 20, 24, 30, 40, 48)
# self.seqhw = (6, 8, 10, 12, 14, 15, 16, 20, 24, 30)
#
# self.base_img_size = to_2tuple(base_img_size)
# self.base_patch_size = to_2tuple(base_patch_size)
# self.base_grid_size = tuple([i // p for i, p in zip(self.base_img_size, self.base_patch_size)])
# self.base_num_patches = self.base_grid_size[0] * self.base_grid_size[1]
#
# self.flatten = flatten
# self.proj = nn.Conv2d(in_chans, embed_dim, kernel_size=self.patch_size, stride=self.patch_size, bias=bias)
# self.norm = norm_layer(embed_dim) if norm_layer else nn.Identity()
#
# def forward(self, x):
# B, C, H, W = x.shape
#
# if self.patch_size == self.base_patch_size:
# weight = self.proj.weight
# else:
# weight = resample_patch_embed(self.proj.weight, self.patch_size)
# patch_size = self.patch_size
# x = F.conv2d(x, weight, bias=self.proj.bias, stride=patch_size)
# if self.flatten:
# x = x.flatten(2).transpose(1, 2) # BCHW -> BNC
# x = self.norm(x)
# return x