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YaoFANGUK
308
backend/ppocr/modeling/transforms/tps.py
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308
backend/ppocr/modeling/transforms/tps.py
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# copyright (c) 2020 PaddlePaddle Authors. All Rights Reserve.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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This code is refer from:
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https://github.com/clovaai/deep-text-recognition-benchmark/blob/master/modules/transformation.py
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"""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import print_function
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import math
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import paddle
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from paddle import nn, ParamAttr
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from paddle.nn import functional as F
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import numpy as np
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class ConvBNLayer(nn.Layer):
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def __init__(self,
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in_channels,
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out_channels,
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kernel_size,
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stride=1,
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groups=1,
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act=None,
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name=None):
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super(ConvBNLayer, self).__init__()
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self.conv = nn.Conv2D(
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in_channels=in_channels,
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out_channels=out_channels,
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kernel_size=kernel_size,
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stride=stride,
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padding=(kernel_size - 1) // 2,
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groups=groups,
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weight_attr=ParamAttr(name=name + "_weights"),
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bias_attr=False)
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bn_name = "bn_" + name
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self.bn = nn.BatchNorm(
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out_channels,
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act=act,
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param_attr=ParamAttr(name=bn_name + '_scale'),
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bias_attr=ParamAttr(bn_name + '_offset'),
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moving_mean_name=bn_name + '_mean',
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moving_variance_name=bn_name + '_variance')
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def forward(self, x):
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x = self.conv(x)
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x = self.bn(x)
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return x
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class LocalizationNetwork(nn.Layer):
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def __init__(self, in_channels, num_fiducial, loc_lr, model_name):
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super(LocalizationNetwork, self).__init__()
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self.F = num_fiducial
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F = num_fiducial
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if model_name == "large":
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num_filters_list = [64, 128, 256, 512]
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fc_dim = 256
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else:
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num_filters_list = [16, 32, 64, 128]
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fc_dim = 64
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self.block_list = []
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for fno in range(0, len(num_filters_list)):
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num_filters = num_filters_list[fno]
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name = "loc_conv%d" % fno
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conv = self.add_sublayer(
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name,
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ConvBNLayer(
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in_channels=in_channels,
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out_channels=num_filters,
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kernel_size=3,
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act='relu',
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name=name))
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self.block_list.append(conv)
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if fno == len(num_filters_list) - 1:
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pool = nn.AdaptiveAvgPool2D(1)
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else:
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pool = nn.MaxPool2D(kernel_size=2, stride=2, padding=0)
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in_channels = num_filters
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self.block_list.append(pool)
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name = "loc_fc1"
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stdv = 1.0 / math.sqrt(num_filters_list[-1] * 1.0)
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self.fc1 = nn.Linear(
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in_channels,
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fc_dim,
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weight_attr=ParamAttr(
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learning_rate=loc_lr,
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name=name + "_w",
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initializer=nn.initializer.Uniform(-stdv, stdv)),
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bias_attr=ParamAttr(name=name + '.b_0'),
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name=name)
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# Init fc2 in LocalizationNetwork
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initial_bias = self.get_initial_fiducials()
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initial_bias = initial_bias.reshape(-1)
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name = "loc_fc2"
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param_attr = ParamAttr(
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learning_rate=loc_lr,
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initializer=nn.initializer.Assign(np.zeros([fc_dim, F * 2])),
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name=name + "_w")
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bias_attr = ParamAttr(
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learning_rate=loc_lr,
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initializer=nn.initializer.Assign(initial_bias),
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name=name + "_b")
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self.fc2 = nn.Linear(
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fc_dim,
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F * 2,
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weight_attr=param_attr,
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bias_attr=bias_attr,
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name=name)
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self.out_channels = F * 2
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def forward(self, x):
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"""
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Estimating parameters of geometric transformation
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Args:
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image: input
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Return:
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batch_C_prime: the matrix of the geometric transformation
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"""
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B = x.shape[0]
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i = 0
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for block in self.block_list:
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x = block(x)
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x = x.squeeze(axis=2).squeeze(axis=2)
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x = self.fc1(x)
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x = F.relu(x)
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x = self.fc2(x)
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x = x.reshape(shape=[-1, self.F, 2])
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return x
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def get_initial_fiducials(self):
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""" see RARE paper Fig. 6 (a) """
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F = self.F
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ctrl_pts_x = np.linspace(-1.0, 1.0, int(F / 2))
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ctrl_pts_y_top = np.linspace(0.0, -1.0, num=int(F / 2))
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ctrl_pts_y_bottom = np.linspace(1.0, 0.0, num=int(F / 2))
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ctrl_pts_top = np.stack([ctrl_pts_x, ctrl_pts_y_top], axis=1)
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ctrl_pts_bottom = np.stack([ctrl_pts_x, ctrl_pts_y_bottom], axis=1)
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initial_bias = np.concatenate([ctrl_pts_top, ctrl_pts_bottom], axis=0)
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return initial_bias
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class GridGenerator(nn.Layer):
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def __init__(self, in_channels, num_fiducial):
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super(GridGenerator, self).__init__()
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self.eps = 1e-6
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self.F = num_fiducial
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name = "ex_fc"
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initializer = nn.initializer.Constant(value=0.0)
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param_attr = ParamAttr(
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learning_rate=0.0, initializer=initializer, name=name + "_w")
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bias_attr = ParamAttr(
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learning_rate=0.0, initializer=initializer, name=name + "_b")
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self.fc = nn.Linear(
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in_channels,
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6,
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weight_attr=param_attr,
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bias_attr=bias_attr,
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name=name)
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def forward(self, batch_C_prime, I_r_size):
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"""
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Generate the grid for the grid_sampler.
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Args:
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batch_C_prime: the matrix of the geometric transformation
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I_r_size: the shape of the input image
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Return:
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batch_P_prime: the grid for the grid_sampler
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"""
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C = self.build_C_paddle()
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P = self.build_P_paddle(I_r_size)
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inv_delta_C_tensor = self.build_inv_delta_C_paddle(C).astype('float32')
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P_hat_tensor = self.build_P_hat_paddle(
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C, paddle.to_tensor(P)).astype('float32')
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inv_delta_C_tensor.stop_gradient = True
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P_hat_tensor.stop_gradient = True
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batch_C_ex_part_tensor = self.get_expand_tensor(batch_C_prime)
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batch_C_ex_part_tensor.stop_gradient = True
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batch_C_prime_with_zeros = paddle.concat(
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[batch_C_prime, batch_C_ex_part_tensor], axis=1)
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batch_T = paddle.matmul(inv_delta_C_tensor, batch_C_prime_with_zeros)
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batch_P_prime = paddle.matmul(P_hat_tensor, batch_T)
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return batch_P_prime
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def build_C_paddle(self):
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""" Return coordinates of fiducial points in I_r; C """
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F = self.F
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ctrl_pts_x = paddle.linspace(-1.0, 1.0, int(F / 2), dtype='float64')
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ctrl_pts_y_top = -1 * paddle.ones([int(F / 2)], dtype='float64')
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ctrl_pts_y_bottom = paddle.ones([int(F / 2)], dtype='float64')
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ctrl_pts_top = paddle.stack([ctrl_pts_x, ctrl_pts_y_top], axis=1)
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ctrl_pts_bottom = paddle.stack([ctrl_pts_x, ctrl_pts_y_bottom], axis=1)
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C = paddle.concat([ctrl_pts_top, ctrl_pts_bottom], axis=0)
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return C # F x 2
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def build_P_paddle(self, I_r_size):
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I_r_height, I_r_width = I_r_size
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I_r_grid_x = (paddle.arange(
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-I_r_width, I_r_width, 2, dtype='float64') + 1.0
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) / paddle.to_tensor(np.array([I_r_width]))
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I_r_grid_y = (paddle.arange(
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-I_r_height, I_r_height, 2, dtype='float64') + 1.0
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) / paddle.to_tensor(np.array([I_r_height]))
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# P: self.I_r_width x self.I_r_height x 2
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P = paddle.stack(paddle.meshgrid(I_r_grid_x, I_r_grid_y), axis=2)
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P = paddle.transpose(P, perm=[1, 0, 2])
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# n (= self.I_r_width x self.I_r_height) x 2
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return P.reshape([-1, 2])
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def build_inv_delta_C_paddle(self, C):
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""" Return inv_delta_C which is needed to calculate T """
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F = self.F
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hat_eye = paddle.eye(F, dtype='float64') # F x F
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hat_C = paddle.norm(
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C.reshape([1, F, 2]) - C.reshape([F, 1, 2]), axis=2) + hat_eye
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hat_C = (hat_C**2) * paddle.log(hat_C)
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delta_C = paddle.concat( # F+3 x F+3
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[
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paddle.concat(
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[paddle.ones(
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(F, 1), dtype='float64'), C, hat_C], axis=1), # F x F+3
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paddle.concat(
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[
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paddle.zeros(
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(2, 3), dtype='float64'), paddle.transpose(
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C, perm=[1, 0])
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],
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axis=1), # 2 x F+3
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paddle.concat(
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[
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paddle.zeros(
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(1, 3), dtype='float64'), paddle.ones(
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(1, F), dtype='float64')
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],
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axis=1) # 1 x F+3
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],
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axis=0)
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inv_delta_C = paddle.inverse(delta_C)
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return inv_delta_C # F+3 x F+3
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def build_P_hat_paddle(self, C, P):
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F = self.F
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eps = self.eps
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n = P.shape[0] # n (= self.I_r_width x self.I_r_height)
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# P_tile: n x 2 -> n x 1 x 2 -> n x F x 2
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P_tile = paddle.tile(paddle.unsqueeze(P, axis=1), (1, F, 1))
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C_tile = paddle.unsqueeze(C, axis=0) # 1 x F x 2
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P_diff = P_tile - C_tile # n x F x 2
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# rbf_norm: n x F
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rbf_norm = paddle.norm(P_diff, p=2, axis=2, keepdim=False)
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# rbf: n x F
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rbf = paddle.multiply(
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paddle.square(rbf_norm), paddle.log(rbf_norm + eps))
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P_hat = paddle.concat(
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[paddle.ones(
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(n, 1), dtype='float64'), P, rbf], axis=1)
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return P_hat # n x F+3
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def get_expand_tensor(self, batch_C_prime):
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B, H, C = batch_C_prime.shape
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batch_C_prime = batch_C_prime.reshape([B, H * C])
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batch_C_ex_part_tensor = self.fc(batch_C_prime)
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batch_C_ex_part_tensor = batch_C_ex_part_tensor.reshape([-1, 3, 2])
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return batch_C_ex_part_tensor
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class TPS(nn.Layer):
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def __init__(self, in_channels, num_fiducial, loc_lr, model_name):
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super(TPS, self).__init__()
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self.loc_net = LocalizationNetwork(in_channels, num_fiducial, loc_lr,
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model_name)
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self.grid_generator = GridGenerator(self.loc_net.out_channels,
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num_fiducial)
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self.out_channels = in_channels
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def forward(self, image):
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image.stop_gradient = False
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batch_C_prime = self.loc_net(image)
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batch_P_prime = self.grid_generator(batch_C_prime, image.shape[2:])
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batch_P_prime = batch_P_prime.reshape(
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[-1, image.shape[2], image.shape[3], 2])
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batch_I_r = F.grid_sample(x=image, grid=batch_P_prime)
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return batch_I_r
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