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rec_sar_head.py
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# copyright (c) 2021 PaddlePaddle Authors. All Rights Reserve.
#
# 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.
"""
This code is refer from:
https://github.com/open-mmlab/mmocr/blob/main/mmocr/models/textrecog/encoders/sar_encoder.py
https://github.com/open-mmlab/mmocr/blob/main/mmocr/models/textrecog/decoders/sar_decoder.py
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import math
import paddle
from paddle import ParamAttr
import paddle.nn as nn
import paddle.nn.functional as F
class SAREncoder(nn.Layer):
"""
Args:
enc_bi_rnn (bool): If True, use bidirectional RNN in encoder.
enc_drop_rnn (float): Dropout probability of RNN layer in encoder.
enc_gru (bool): If True, use GRU, else LSTM in encoder.
d_model (int): Dim of channels from backbone.
d_enc (int): Dim of encoder RNN layer.
mask (bool): If True, mask padding in RNN sequence.
"""
def __init__(self,
enc_bi_rnn=False,
enc_drop_rnn=0.1,
enc_gru=False,
d_model=512,
d_enc=512,
mask=True,
**kwargs):
super().__init__()
assert isinstance(enc_bi_rnn, bool)
assert isinstance(enc_drop_rnn, (int, float))
assert 0 <= enc_drop_rnn < 1.0
assert isinstance(enc_gru, bool)
assert isinstance(d_model, int)
assert isinstance(d_enc, int)
assert isinstance(mask, bool)
self.enc_bi_rnn = enc_bi_rnn
self.enc_drop_rnn = enc_drop_rnn
self.mask = mask
# LSTM Encoder
if enc_bi_rnn:
direction = 'bidirectional'
else:
direction = 'forward'
kwargs = dict(
input_size=d_model,
hidden_size=d_enc,
num_layers=2,
time_major=False,
dropout=enc_drop_rnn,
direction=direction)
if enc_gru:
self.rnn_encoder = nn.GRU(**kwargs)
else:
self.rnn_encoder = nn.LSTM(**kwargs)
# global feature transformation
encoder_rnn_out_size = d_enc * (int(enc_bi_rnn) + 1)
self.linear = nn.Linear(encoder_rnn_out_size, encoder_rnn_out_size)
def forward(self, feat, img_metas=None):
if img_metas is not None:
assert len(img_metas[0]) == feat.shape[0]
valid_ratios = None
if img_metas is not None and self.mask:
valid_ratios = img_metas[-1]
h_feat = feat.shape[2] # bsz c h w
feat_v = F.max_pool2d(
feat, kernel_size=(h_feat, 1), stride=1, padding=0)
feat_v = feat_v.squeeze(2) # bsz * C * W
feat_v = paddle.transpose(feat_v, perm=[0, 2, 1]) # bsz * W * C
holistic_feat = self.rnn_encoder(feat_v)[0] # bsz * T * C
if valid_ratios is not None:
valid_hf = []
T = holistic_feat.shape[1]
for i, valid_ratio in enumerate(valid_ratios):
valid_step = min(T, math.ceil(T * valid_ratio)) - 1
valid_hf.append(holistic_feat[i, valid_step, :])
valid_hf = paddle.stack(valid_hf, axis=0)
else:
valid_hf = holistic_feat[:, -1, :] # bsz * C
holistic_feat = self.linear(valid_hf) # bsz * C
return holistic_feat
class BaseDecoder(nn.Layer):
def __init__(self, **kwargs):
super().__init__()
def forward_train(self, feat, out_enc, targets, img_metas):
raise NotImplementedError
def forward_test(self, feat, out_enc, img_metas):
raise NotImplementedError
def forward(self,
feat,
out_enc,
label=None,
img_metas=None,
train_mode=True):
self.train_mode = train_mode
if train_mode:
return self.forward_train(feat, out_enc, label, img_metas)
return self.forward_test(feat, out_enc, img_metas)
class ParallelSARDecoder(BaseDecoder):
"""
Args:
out_channels (int): Output class number.
enc_bi_rnn (bool): If True, use bidirectional RNN in encoder.
dec_bi_rnn (bool): If True, use bidirectional RNN in decoder.
dec_drop_rnn (float): Dropout of RNN layer in decoder.
dec_gru (bool): If True, use GRU, else LSTM in decoder.
d_model (int): Dim of channels from backbone.
d_enc (int): Dim of encoder RNN layer.
d_k (int): Dim of channels of attention module.
pred_dropout (float): Dropout probability of prediction layer.
max_seq_len (int): Maximum sequence length for decoding.
mask (bool): If True, mask padding in feature map.
start_idx (int): Index of start token.
padding_idx (int): Index of padding token.
pred_concat (bool): If True, concat glimpse feature from
attention with holistic feature and hidden state.
"""
def __init__(
self,
out_channels, # 90 + unknown + start + padding
enc_bi_rnn=False,
dec_bi_rnn=False,
dec_drop_rnn=0.0,
dec_gru=False,
d_model=512,
d_enc=512,
d_k=64,
pred_dropout=0.1,
max_text_length=30,
mask=True,
pred_concat=True,
**kwargs):
super().__init__()
self.num_classes = out_channels
self.enc_bi_rnn = enc_bi_rnn
self.d_k = d_k
self.start_idx = out_channels - 2
self.padding_idx = out_channels - 1
self.max_seq_len = max_text_length
self.mask = mask
self.pred_concat = pred_concat
encoder_rnn_out_size = d_enc * (int(enc_bi_rnn) + 1)
decoder_rnn_out_size = encoder_rnn_out_size * (int(dec_bi_rnn) + 1)
# 2D attention layer
self.conv1x1_1 = nn.Linear(decoder_rnn_out_size, d_k)
self.conv3x3_1 = nn.Conv2D(
d_model, d_k, kernel_size=3, stride=1, padding=1)
self.conv1x1_2 = nn.Linear(d_k, 1)
# Decoder RNN layer
if dec_bi_rnn:
direction = 'bidirectional'
else:
direction = 'forward'
kwargs = dict(
input_size=encoder_rnn_out_size,
hidden_size=encoder_rnn_out_size,
num_layers=2,
time_major=False,
dropout=dec_drop_rnn,
direction=direction)
if dec_gru:
self.rnn_decoder = nn.GRU(**kwargs)
else:
self.rnn_decoder = nn.LSTM(**kwargs)
# Decoder input embedding
self.embedding = nn.Embedding(
self.num_classes,
encoder_rnn_out_size,
padding_idx=self.padding_idx)
# Prediction layer
self.pred_dropout = nn.Dropout(pred_dropout)
pred_num_classes = self.num_classes - 1
if pred_concat:
fc_in_channel = decoder_rnn_out_size + d_model + d_enc
else:
fc_in_channel = d_model
self.prediction = nn.Linear(fc_in_channel, pred_num_classes)
def _2d_attention(self,
decoder_input,
feat,
holistic_feat,
valid_ratios=None):
y = self.rnn_decoder(decoder_input)[0]
# y: bsz * (seq_len + 1) * hidden_size
attn_query = self.conv1x1_1(y) # bsz * (seq_len + 1) * attn_size
bsz, seq_len, attn_size = attn_query.shape
attn_query = paddle.unsqueeze(attn_query, axis=[3, 4])
# (bsz, seq_len + 1, attn_size, 1, 1)
attn_key = self.conv3x3_1(feat)
# bsz * attn_size * h * w
attn_key = attn_key.unsqueeze(1)
# bsz * 1 * attn_size * h * w
attn_weight = paddle.tanh(paddle.add(attn_key, attn_query))
# bsz * (seq_len + 1) * attn_size * h * w
attn_weight = paddle.transpose(attn_weight, perm=[0, 1, 3, 4, 2])
# bsz * (seq_len + 1) * h * w * attn_size
attn_weight = self.conv1x1_2(attn_weight)
# bsz * (seq_len + 1) * h * w * 1
bsz, T, h, w, c = attn_weight.shape
assert c == 1
if valid_ratios is not None:
# cal mask of attention weight
for i, valid_ratio in enumerate(valid_ratios):
valid_width = min(w, math.ceil(w * valid_ratio))
if valid_width < w:
attn_weight[i, :, :, valid_width:, :] = float('-inf')
attn_weight = paddle.reshape(attn_weight, [bsz, T, -1])
attn_weight = F.softmax(attn_weight, axis=-1)
attn_weight = paddle.reshape(attn_weight, [bsz, T, h, w, c])
attn_weight = paddle.transpose(attn_weight, perm=[0, 1, 4, 2, 3])
# attn_weight: bsz * T * c * h * w
# feat: bsz * c * h * w
attn_feat = paddle.sum(paddle.multiply(feat.unsqueeze(1), attn_weight),
(3, 4),
keepdim=False)
# bsz * (seq_len + 1) * C
# Linear transformation
if self.pred_concat:
hf_c = holistic_feat.shape[-1]
holistic_feat = paddle.expand(
holistic_feat, shape=[bsz, seq_len, hf_c])
y = self.prediction(paddle.concat((y, attn_feat, holistic_feat), 2))
else:
y = self.prediction(attn_feat)
# bsz * (seq_len + 1) * num_classes
if self.train_mode:
y = self.pred_dropout(y)
return y
def forward_train(self, feat, out_enc, label, img_metas):
'''
img_metas: [label, valid_ratio]
'''
if img_metas is not None:
assert len(img_metas[0]) == feat.shape[0]
valid_ratios = None
if img_metas is not None and self.mask:
valid_ratios = img_metas[-1]
lab_embedding = self.embedding(label)
# bsz * seq_len * emb_dim
out_enc = out_enc.unsqueeze(1)
# bsz * 1 * emb_dim
in_dec = paddle.concat((out_enc, lab_embedding), axis=1)
# bsz * (seq_len + 1) * C
out_dec = self._2d_attention(
in_dec, feat, out_enc, valid_ratios=valid_ratios)
# bsz * (seq_len + 1) * num_classes
return out_dec[:, 1:, :] # bsz * seq_len * num_classes
def forward_test(self, feat, out_enc, img_metas):
if img_metas is not None:
assert len(img_metas[0]) == feat.shape[0]
valid_ratios = None
if img_metas is not None and self.mask:
valid_ratios = img_metas[-1]
seq_len = self.max_seq_len
bsz = feat.shape[0]
start_token = paddle.full(
(bsz, ), fill_value=self.start_idx, dtype='int64')
# bsz
start_token = self.embedding(start_token)
# bsz * emb_dim
emb_dim = start_token.shape[1]
start_token = start_token.unsqueeze(1)
start_token = paddle.expand(start_token, shape=[bsz, seq_len, emb_dim])
# bsz * seq_len * emb_dim
out_enc = out_enc.unsqueeze(1)
# bsz * 1 * emb_dim
decoder_input = paddle.concat((out_enc, start_token), axis=1)
# bsz * (seq_len + 1) * emb_dim
outputs = []
for i in range(1, seq_len + 1):
decoder_output = self._2d_attention(
decoder_input, feat, out_enc, valid_ratios=valid_ratios)
char_output = decoder_output[:, i, :] # bsz * num_classes
char_output = F.softmax(char_output, -1)
outputs.append(char_output)
max_idx = paddle.argmax(char_output, axis=1, keepdim=False)
char_embedding = self.embedding(max_idx) # bsz * emb_dim
if i < seq_len:
decoder_input[:, i + 1, :] = char_embedding
outputs = paddle.stack(outputs, 1) # bsz * seq_len * num_classes
return outputs
class SARHead(nn.Layer):
def __init__(self,
out_channels,
enc_bi_rnn=False,
enc_drop_rnn=0.1,
enc_gru=False,
dec_bi_rnn=False,
dec_drop_rnn=0.0,
dec_gru=False,
d_k=512,
pred_dropout=0.1,
max_text_length=30,
pred_concat=True,
**kwargs):
super(SARHead, self).__init__()
# encoder module
self.encoder = SAREncoder(
enc_bi_rnn=enc_bi_rnn, enc_drop_rnn=enc_drop_rnn, enc_gru=enc_gru)
# decoder module
self.decoder = ParallelSARDecoder(
out_channels=out_channels,
enc_bi_rnn=enc_bi_rnn,
dec_bi_rnn=dec_bi_rnn,
dec_drop_rnn=dec_drop_rnn,
dec_gru=dec_gru,
d_k=d_k,
pred_dropout=pred_dropout,
max_text_length=max_text_length,
pred_concat=pred_concat)
def forward(self, feat, targets=None):
'''
img_metas: [label, valid_ratio]
'''
holistic_feat = self.encoder(feat, targets) # bsz c
if self.training:
label = targets[0] # label
label = paddle.to_tensor(label, dtype='int64')
final_out = self.decoder(
feat, holistic_feat, label, img_metas=targets)
if not self.training:
final_out = self.decoder(
feat,
holistic_feat,
label=None,
img_metas=targets,
train_mode=False)
# (bsz, seq_len, num_classes)
return final_out