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# Copyright (c) Facebook, Inc. and its affiliates. | |
# # Modified by Bowen Cheng from: https://github.com/facebookresearch/detr/blob/master/models/position_encoding.py | |
# Copyright (c) Meta Platforms, Inc. All Rights Reserved | |
""" | |
Various positional encodings for the transformer. | |
""" | |
import math | |
import torch | |
from torch import nn | |
class PositionEmbeddingSine(nn.Module): | |
""" | |
This is a more standard version of the position embedding, very similar to the one | |
used by the Attention is all you need paper, generalized to work on images. | |
""" | |
def __init__( | |
self, num_pos_feats=64, temperature=10000, normalize=False, scale=None | |
): | |
super().__init__() | |
self.num_pos_feats = num_pos_feats | |
self.temperature = temperature | |
self.normalize = normalize | |
if scale is not None and normalize is False: | |
raise ValueError("normalize should be True if scale is passed") | |
if scale is None: | |
scale = 2 * math.pi | |
self.scale = scale | |
def forward(self, x, mask=None): | |
if mask is None: | |
mask = torch.zeros( | |
(x.size(0), x.size(2), x.size(3)), device=x.device, dtype=torch.bool | |
) | |
not_mask = ~mask | |
y_embed = not_mask.cumsum(1, dtype=torch.float32) | |
x_embed = not_mask.cumsum(2, dtype=torch.float32) | |
if self.normalize: | |
eps = 1e-6 | |
y_embed = y_embed / (y_embed[:, -1:, :] + eps) * self.scale | |
x_embed = x_embed / (x_embed[:, :, -1:] + eps) * self.scale | |
dim_t = torch.arange(self.num_pos_feats, dtype=torch.float32, device=x.device) | |
dim_t = self.temperature ** (2 * (dim_t // 2) / self.num_pos_feats) | |
pos_x = x_embed[:, :, :, None] / dim_t | |
pos_y = y_embed[:, :, :, None] / dim_t | |
pos_x = torch.stack( | |
(pos_x[:, :, :, 0::2].sin(), pos_x[:, :, :, 1::2].cos()), dim=4 | |
).flatten(3) | |
pos_y = torch.stack( | |
(pos_y[:, :, :, 0::2].sin(), pos_y[:, :, :, 1::2].cos()), dim=4 | |
).flatten(3) | |
pos = torch.cat((pos_y, pos_x), dim=3).permute(0, 3, 1, 2) | |
return pos | |