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# coding=utf-8 | |
# Copyright 2022 The IDEA Authors. 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. | |
# ------------------------------------------------------------------------------------------------ | |
# Various positional encodings for the transformer. | |
# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved | |
# Copyright (c) OpenMMLab. All rights reserved. | |
# ------------------------------------------------------------------------------------------------ | |
# Modified from: | |
# https://github.com/facebookresearch/detr/blob/main/models/position_encoding.py | |
# https://github.com/open-mmlab/mmdetection/blob/master/mmdet/models/utils/positional_encoding.py | |
# ------------------------------------------------------------------------------------------------ | |
import math | |
import torch | |
import torch.nn as nn | |
class PositionEmbeddingSine(nn.Module): | |
"""Sinusoidal position embedding used in DETR model. | |
Please see `End-to-End Object Detection with Transformers | |
<https://arxiv.org/pdf/2005.12872>`_ for more details. | |
Args: | |
num_pos_feats (int): The feature dimension for each position along | |
x-axis or y-axis. The final returned dimension for each position | |
is 2 times of the input value. | |
temperature (int, optional): The temperature used for scaling | |
the position embedding. Default: 10000. | |
scale (float, optional): A scale factor that scales the position | |
embedding. The scale will be used only when `normalize` is True. | |
Default: 2*pi. | |
eps (float, optional): A value added to the denominator for numerical | |
stability. Default: 1e-6. | |
offset (float): An offset added to embed when doing normalization. | |
normalize (bool, optional): Whether to normalize the position embedding. | |
Default: False. | |
""" | |
def __init__( | |
self, | |
num_pos_feats: int = 64, | |
temperature: int = 10000, | |
scale: float = 2 * math.pi, | |
eps: float = 1e-6, | |
offset: float = 0.0, | |
normalize: bool = False, | |
): | |
super().__init__() | |
if normalize: | |
assert isinstance(scale, (float, int)), ( | |
"when normalize is set," | |
"scale should be provided and in float or int type, " | |
f"found {type(scale)}" | |
) | |
self.num_pos_feats = num_pos_feats | |
self.temperature = temperature | |
self.normalize = normalize | |
self.scale = scale | |
self.eps = eps | |
self.offset = offset | |
def forward(self, mask: torch.Tensor, **kwargs) -> torch.Tensor: | |
"""Forward function for `PositionEmbeddingSine`. | |
Args: | |
mask (torch.Tensor): ByteTensor mask. Non-zero values representing | |
ignored positions, while zero values means valid positions | |
for the input tensor. Shape as `(bs, h, w)`. | |
Returns: | |
torch.Tensor: Returned position embedding with | |
shape `(bs, num_pos_feats * 2, h, w)` | |
""" | |
assert mask is not None | |
not_mask = ~mask | |
y_embed = not_mask.cumsum(1, dtype=torch.float32) | |
x_embed = not_mask.cumsum(2, dtype=torch.float32) | |
if self.normalize: | |
y_embed = (y_embed + self.offset) / (y_embed[:, -1:, :] + self.eps) * self.scale | |
x_embed = (x_embed + self.offset) / (x_embed[:, :, -1:] + self.eps) * self.scale | |
dim_t = torch.arange(self.num_pos_feats, dtype=torch.float32, device=mask.device) | |
dim_t = self.temperature ** ( | |
2 * torch.div(dim_t, 2, rounding_mode="floor") / self.num_pos_feats | |
) | |
pos_x = x_embed[:, :, :, None] / dim_t | |
pos_y = y_embed[:, :, :, None] / dim_t | |
# use view as mmdet instead of flatten for dynamically exporting to ONNX | |
B, H, W = mask.size() | |
pos_x = torch.stack((pos_x[:, :, :, 0::2].sin(), pos_x[:, :, :, 1::2].cos()), dim=4).view( | |
B, H, W, -1 | |
) | |
pos_y = torch.stack((pos_y[:, :, :, 0::2].sin(), pos_y[:, :, :, 1::2].cos()), dim=4).view( | |
B, H, W, -1 | |
) | |
pos = torch.cat((pos_y, pos_x), dim=3).permute(0, 3, 1, 2) | |
return pos | |
class PositionEmbeddingLearned(nn.Module): | |
""" | |
Position embedding with learnable embedding weights. | |
Args: | |
num_pos_feats (int): The feature dimension for each position along | |
x-axis or y-axis. The final returned dimension for each position | |
is 2 times of the input value. | |
row_num_embed (int, optional): The dictionary size of row embeddings. | |
Default: 50. | |
col_num_embed (int, optional): The dictionary size of column embeddings. | |
Default: 50. | |
""" | |
def __init__( | |
self, | |
num_pos_feats: int = 256, | |
row_num_embed: int = 50, | |
col_num_embed: int = 50, | |
): | |
super().__init__() | |
self.row_embed = nn.Embedding(row_num_embed, num_pos_feats) | |
self.col_embed = nn.Embedding(col_num_embed, num_pos_feats) | |
self.num_pos_feats = num_pos_feats | |
self.row_num_embed = row_num_embed | |
self.col_num_embed = col_num_embed | |
self.reset_parameters() | |
def reset_parameters(self): | |
nn.init.uniform_(self.row_embed.weight) | |
nn.init.uniform_(self.col_embed.weight) | |
def forward(self, mask): | |
"""Forward function for `PositionEmbeddingLearned`. | |
Args: | |
mask (torch.Tensor): ByteTensor mask. Non-zero values representing | |
ignored positions, while zero values means valid positions | |
for the input tensor. Shape as `(bs, h, w)`. | |
Returns: | |
torch.Tensor: Returned position embedding with | |
shape `(bs, num_pos_feats * 2, h, w)` | |
""" | |
h, w = mask.shape[-2:] | |
x = torch.arange(w, device=mask.device) | |
y = torch.arange(h, device=mask.device) | |
x_emb = self.col_embed(x) | |
y_emb = self.row_embed(y) | |
pos = ( | |
torch.cat( | |
[ | |
x_emb.unsqueeze(0).repeat(h, 1, 1), | |
y_emb.unsqueeze(1).repeat(1, w, 1), | |
], | |
dim=-1, | |
) | |
.permute(2, 0, 1) | |
.unsqueeze(0) | |
.repeat(mask.shape[0], 1, 1, 1) | |
) | |
return pos | |
def get_sine_pos_embed( | |
pos_tensor: torch.Tensor, | |
num_pos_feats: int = 128, | |
temperature: int = 10000, | |
exchange_xy: bool = True, | |
) -> torch.Tensor: | |
"""generate sine position embedding from a position tensor | |
Args: | |
pos_tensor (torch.Tensor): Shape as `(None, n)`. | |
num_pos_feats (int): projected shape for each float in the tensor. Default: 128 | |
temperature (int): The temperature used for scaling | |
the position embedding. Default: 10000. | |
exchange_xy (bool, optional): exchange pos x and pos y. \ | |
For example, input tensor is `[x, y]`, the results will # noqa | |
be `[pos(y), pos(x)]`. Defaults: True. | |
Returns: | |
torch.Tensor: Returned position embedding # noqa | |
with shape `(None, n * num_pos_feats)`. | |
""" | |
scale = 2 * math.pi | |
dim_t = torch.arange(num_pos_feats, dtype=torch.float32, device=pos_tensor.device) | |
dim_t = temperature ** (2 * torch.div(dim_t, 2, rounding_mode="floor") / num_pos_feats) | |
def sine_func(x: torch.Tensor): | |
sin_x = x * scale / dim_t | |
sin_x = torch.stack((sin_x[:, :, 0::2].sin(), sin_x[:, :, 1::2].cos()), dim=3).flatten(2) | |
return sin_x | |
pos_res = [sine_func(x) for x in pos_tensor.split([1] * pos_tensor.shape[-1], dim=-1)] | |
if exchange_xy: | |
pos_res[0], pos_res[1] = pos_res[1], pos_res[0] | |
pos_res = torch.cat(pos_res, dim=2) | |
return pos_res | |