character.py

# Copyright (c) 2020 PaddlePaddle 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.
import string

import numpy as np


class CharacterOps(object):
    """ Convert between text-label and text-index
    Args:
        config: config from yaml file
    """

    def __init__(self, config):
        self.character_type = config['character_type']
        self.max_text_len = config['max_text_length']
        if self.character_type == "en":
            self.character_str = "0123456789abcdefghijklmnopqrstuvwxyz"
            dict_character = list(self.character_str)
        # use the custom dictionary
        elif self.character_type == "ch":
            character_dict_path = config['character_dict_path']
            add_space = False
            if 'use_space_char' in config:
                add_space = config['use_space_char']
            self.character_str = []
            with open(character_dict_path, "rb") as fin:
                lines = fin.readlines()
                for line in lines:
                    line = line.decode('utf-8').strip("\n").strip("\r\n")
                    self.character_str.append(line)
            if add_space:
                self.character_str.append(" ")
            dict_character = list(self.character_str)
        elif self.character_type == "en_sensitive":
            # same with ASTER setting (use 94 char).
            self.character_str = string.printable[:-6]
            dict_character = list(self.character_str)
        else:
            self.character_str = None
        self.beg_str = "sos"
        self.end_str = "eos"

        dict_character = self.add_special_char(dict_character)
        self.dict = {}
        for i, char in enumerate(dict_character):
            self.dict[char] = i
        self.character = dict_character

    def add_special_char(self, dict_character):
        dict_character = ['blank'] + dict_character
        return dict_character

    def encode(self, text):
        """convert text-label into text-index.
        input:
            text: text labels of each image. [batch_size]

        output:
            text: concatenated text index for CTCLoss.
                    [sum(text_lengths)] = [text_index_0 + text_index_1 + ... + text_index_(n - 1)]
            length: length of each text. [batch_size]
        """
        if self.character_type == "en":
            text = text.lower()

        text_list = []
        for char in text:
            if char not in self.dict:
                continue
            text_list.append(self.dict[char])
        text = np.array(text_list)
        return text

    def decode(self, text_index, text_prob=None, is_remove_duplicate=False):
        """ convert text-index into text-label. """
        result_list = []
        ignored_tokens = self.get_ignored_tokens()
        batch_size = len(text_index)
        for batch_idx in range(batch_size):
            selection = np.ones(len(text_index[batch_idx]), dtype=bool)
            if is_remove_duplicate:
                selection[1:] = text_index[batch_idx][1:] != text_index[batch_idx][:-1]
            for ignored_token in ignored_tokens:
                selection &= text_index[batch_idx] != ignored_token
            char_list = [self.character[text_id] for text_id in text_index[batch_idx][selection]]
            if text_prob is not None:
                conf_list = text_prob[batch_idx][selection]
            else:
                conf_list = [1] * len(selection)
            if len(conf_list) == 0:
                conf_list = [0]

            text = ''.join(char_list)
            result_list.append((text, np.mean(conf_list).tolist()))
        return result_list

    def get_char_num(self):
        return len(self.character)

    def get_beg_end_flag_idx(self, beg_or_end):
        if self.loss_type == "attention":
            if beg_or_end == "beg":
                idx = np.array(self.dict[self.beg_str])
            elif beg_or_end == "end":
                idx = np.array(self.dict[self.end_str])
            else:
                assert False, "Unsupport type %s in get_beg_end_flag_idx"\
                    % beg_or_end
            return idx
        else:
            err = "error in get_beg_end_flag_idx when using the loss %s"\
                % (self.loss_type)
            assert False, err

    def get_ignored_tokens(self):
        return [0]  # for ctc blank


def cal_predicts_accuracy(char_ops, preds, preds_lod, labels, labels_lod, is_remove_duplicate=False):
    """
    Calculate prediction accuracy
    Args:
        char_ops: CharacterOps
        preds: preds result,text index
        preds_lod: lod tensor of preds
        labels: label of input image, text index
        labels_lod:  lod tensor of label
        is_remove_duplicate: Whether to remove duplicate characters,
                                 The default is False
    Return:
        acc: The accuracy of test set
        acc_num: The correct number of samples predicted
        img_num: The total sample number of the test set
    """
    acc_num = 0
    img_num = 0
    for ino in range(len(labels_lod) - 1):
        beg_no = preds_lod[ino]
        end_no = preds_lod[ino + 1]
        preds_text = preds[beg_no:end_no].reshape(-1)
        preds_text = char_ops.decode(preds_text, is_remove_duplicate)

        beg_no = labels_lod[ino]
        end_no = labels_lod[ino + 1]
        labels_text = labels[beg_no:end_no].reshape(-1)
        labels_text = char_ops.decode(labels_text, is_remove_duplicate)
        img_num += 1

        if preds_text == labels_text:
            acc_num += 1
    acc = acc_num * 1.0 / img_num
    return acc, acc_num, img_num


def cal_predicts_accuracy_srn(char_ops, preds, labels, max_text_len, is_debug=False):
    acc_num = 0
    img_num = 0

    char_num = char_ops.get_char_num()

    total_len = preds.shape[0]
    img_num = int(total_len / max_text_len)
    for i in range(img_num):
        cur_label = []
        cur_pred = []
        for j in range(max_text_len):
            if labels[j + i * max_text_len] != int(char_num - 1):  #0
                cur_label.append(labels[j + i * max_text_len][0])
            else:
                break

        for j in range(max_text_len + 1):
            if j < len(cur_label) and preds[j + i * max_text_len][0] != cur_label[j]:
                break
            elif j == len(cur_label) and j == max_text_len:
                acc_num += 1
                break
            elif j == len(cur_label) and preds[j + i * max_text_len][0] == int(char_num - 1):
                acc_num += 1
                break
    acc = acc_num * 1.0 / img_num
    return acc, acc_num, img_num


def convert_rec_attention_infer_res(preds):
    img_num = preds.shape[0]
    target_lod = [0]
    convert_ids = []
    for ino in range(img_num):
        end_pos = np.where(preds[ino, :] == 1)[0]
        if len(end_pos) <= 1:
            text_list = preds[ino, 1:]
        else:
            text_list = preds[ino, 1:end_pos[1]]
        target_lod.append(target_lod[ino] + len(text_list))
        convert_ids = convert_ids + list(text_list)
    convert_ids = np.array(convert_ids)
    convert_ids = convert_ids.reshape((-1, 1))
    return convert_ids, target_lod


def convert_rec_label_to_lod(ori_labels):
    img_num = len(ori_labels)
    target_lod = [0]
    convert_ids = []
    for ino in range(img_num):
        target_lod.append(target_lod[ino] + len(ori_labels[ino]))
        convert_ids = convert_ids + list(ori_labels[ino])
    convert_ids = np.array(convert_ids)
    convert_ids = convert_ids.reshape((-1, 1))
    return convert_ids, target_lod