# copyright (c) 2022 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/textdet/losses/fce_loss.py """ import numpy as np from paddle import nn import paddle import paddle.nn.functional as F from functools import partial def multi_apply(func, *args, **kwargs): pfunc = partial(func, **kwargs) if kwargs else func map_results = map(pfunc, *args) return tuple(map(list, zip(*map_results))) class FCELoss(nn.Layer): """The class for implementing FCENet loss FCENet(CVPR2021): Fourier Contour Embedding for Arbitrary-shaped Text Detection [https://arxiv.org/abs/2104.10442] Args: fourier_degree (int) : The maximum Fourier transform degree k. num_sample (int) : The sampling points number of regression loss. If it is too small, fcenet tends to be overfitting. ohem_ratio (float): the negative/positive ratio in OHEM. """ def __init__(self, fourier_degree, num_sample, ohem_ratio=3.): super().__init__() self.fourier_degree = fourier_degree self.num_sample = num_sample self.ohem_ratio = ohem_ratio def forward(self, preds, labels): assert isinstance(preds, dict) preds = preds['levels'] p3_maps, p4_maps, p5_maps = labels[1:] assert p3_maps[0].shape[0] == 4 * self.fourier_degree + 5,\ 'fourier degree not equal in FCEhead and FCEtarget' # to tensor gts = [p3_maps, p4_maps, p5_maps] for idx, maps in enumerate(gts): gts[idx] = paddle.to_tensor(np.stack(maps)) losses = multi_apply(self.forward_single, preds, gts) loss_tr = paddle.to_tensor(0.).astype('float32') loss_tcl = paddle.to_tensor(0.).astype('float32') loss_reg_x = paddle.to_tensor(0.).astype('float32') loss_reg_y = paddle.to_tensor(0.).astype('float32') loss_all = paddle.to_tensor(0.).astype('float32') for idx, loss in enumerate(losses): loss_all += sum(loss) if idx == 0: loss_tr += sum(loss) elif idx == 1: loss_tcl += sum(loss) elif idx == 2: loss_reg_x += sum(loss) else: loss_reg_y += sum(loss) results = dict( loss=loss_all, loss_text=loss_tr, loss_center=loss_tcl, loss_reg_x=loss_reg_x, loss_reg_y=loss_reg_y, ) return results def forward_single(self, pred, gt): cls_pred = paddle.transpose(pred[0], (0, 2, 3, 1)) reg_pred = paddle.transpose(pred[1], (0, 2, 3, 1)) gt = paddle.transpose(gt, (0, 2, 3, 1)) k = 2 * self.fourier_degree + 1 tr_pred = paddle.reshape(cls_pred[:, :, :, :2], (-1, 2)) tcl_pred = paddle.reshape(cls_pred[:, :, :, 2:], (-1, 2)) x_pred = paddle.reshape(reg_pred[:, :, :, 0:k], (-1, k)) y_pred = paddle.reshape(reg_pred[:, :, :, k:2 * k], (-1, k)) tr_mask = gt[:, :, :, :1].reshape([-1]) tcl_mask = gt[:, :, :, 1:2].reshape([-1]) train_mask = gt[:, :, :, 2:3].reshape([-1]) x_map = paddle.reshape(gt[:, :, :, 3:3 + k], (-1, k)) y_map = paddle.reshape(gt[:, :, :, 3 + k:], (-1, k)) tr_train_mask = (train_mask * tr_mask).astype('bool') tr_train_mask2 = paddle.concat( [tr_train_mask.unsqueeze(1), tr_train_mask.unsqueeze(1)], axis=1) # tr loss loss_tr = self.ohem(tr_pred, tr_mask, train_mask) # tcl loss loss_tcl = paddle.to_tensor(0.).astype('float32') tr_neg_mask = tr_train_mask.logical_not() tr_neg_mask2 = paddle.concat( [tr_neg_mask.unsqueeze(1), tr_neg_mask.unsqueeze(1)], axis=1) if tr_train_mask.sum().item() > 0: loss_tcl_pos = F.cross_entropy( tcl_pred.masked_select(tr_train_mask2).reshape([-1, 2]), tcl_mask.masked_select(tr_train_mask).astype('int64')) loss_tcl_neg = F.cross_entropy( tcl_pred.masked_select(tr_neg_mask2).reshape([-1, 2]), tcl_mask.masked_select(tr_neg_mask).astype('int64')) loss_tcl = loss_tcl_pos + 0.5 * loss_tcl_neg # regression loss loss_reg_x = paddle.to_tensor(0.).astype('float32') loss_reg_y = paddle.to_tensor(0.).astype('float32') if tr_train_mask.sum().item() > 0: weight = (tr_mask.masked_select(tr_train_mask.astype('bool')) .astype('float32') + tcl_mask.masked_select( tr_train_mask.astype('bool')).astype('float32')) / 2 weight = weight.reshape([-1, 1]) ft_x, ft_y = self.fourier2poly(x_map, y_map) ft_x_pre, ft_y_pre = self.fourier2poly(x_pred, y_pred) dim = ft_x.shape[1] tr_train_mask3 = paddle.concat( [tr_train_mask.unsqueeze(1) for i in range(dim)], axis=1) loss_reg_x = paddle.mean(weight * F.smooth_l1_loss( ft_x_pre.masked_select(tr_train_mask3).reshape([-1, dim]), ft_x.masked_select(tr_train_mask3).reshape([-1, dim]), reduction='none')) loss_reg_y = paddle.mean(weight * F.smooth_l1_loss( ft_y_pre.masked_select(tr_train_mask3).reshape([-1, dim]), ft_y.masked_select(tr_train_mask3).reshape([-1, dim]), reduction='none')) return loss_tr, loss_tcl, loss_reg_x, loss_reg_y def ohem(self, predict, target, train_mask): pos = (target * train_mask).astype('bool') neg = ((1 - target) * train_mask).astype('bool') pos2 = paddle.concat([pos.unsqueeze(1), pos.unsqueeze(1)], axis=1) neg2 = paddle.concat([neg.unsqueeze(1), neg.unsqueeze(1)], axis=1) n_pos = pos.astype('float32').sum() if n_pos.item() > 0: loss_pos = F.cross_entropy( predict.masked_select(pos2).reshape([-1, 2]), target.masked_select(pos).astype('int64'), reduction='sum') loss_neg = F.cross_entropy( predict.masked_select(neg2).reshape([-1, 2]), target.masked_select(neg).astype('int64'), reduction='none') n_neg = min( int(neg.astype('float32').sum().item()), int(self.ohem_ratio * n_pos.astype('float32'))) else: loss_pos = paddle.to_tensor(0.) loss_neg = F.cross_entropy( predict.masked_select(neg2).reshape([-1, 2]), target.masked_select(neg).astype('int64'), reduction='none') n_neg = 100 if len(loss_neg) > n_neg: loss_neg, _ = paddle.topk(loss_neg, n_neg) return (loss_pos + loss_neg.sum()) / (n_pos + n_neg).astype('float32') def fourier2poly(self, real_maps, imag_maps): """Transform Fourier coefficient maps to polygon maps. Args: real_maps (tensor): A map composed of the real parts of the Fourier coefficients, whose shape is (-1, 2k+1) imag_maps (tensor):A map composed of the imag parts of the Fourier coefficients, whose shape is (-1, 2k+1) Returns x_maps (tensor): A map composed of the x value of the polygon represented by n sample points (xn, yn), whose shape is (-1, n) y_maps (tensor): A map composed of the y value of the polygon represented by n sample points (xn, yn), whose shape is (-1, n) """ k_vect = paddle.arange( -self.fourier_degree, self.fourier_degree + 1, dtype='float32').reshape([-1, 1]) i_vect = paddle.arange( 0, self.num_sample, dtype='float32').reshape([1, -1]) transform_matrix = 2 * np.pi / self.num_sample * paddle.matmul(k_vect, i_vect) x1 = paddle.einsum('ak, kn-> an', real_maps, paddle.cos(transform_matrix)) x2 = paddle.einsum('ak, kn-> an', imag_maps, paddle.sin(transform_matrix)) y1 = paddle.einsum('ak, kn-> an', real_maps, paddle.sin(transform_matrix)) y2 = paddle.einsum('ak, kn-> an', imag_maps, paddle.cos(transform_matrix)) x_maps = x1 - x2 y_maps = y1 + y2 return x_maps, y_maps