random_crop_data.py

# copyright (c) 2020 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/WenmuZhou/DBNet.pytorch/blob/master/data_loader/modules/random_crop_data.py
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
from __future__ import unicode_literals

import numpy as np
import cv2
import random


def is_poly_in_rect(poly, x, y, w, h):
    poly = np.array(poly)
    if poly[:, 0].min() < x or poly[:, 0].max() > x + w:
        return False
    if poly[:, 1].min() < y or poly[:, 1].max() > y + h:
        return False
    return True


def is_poly_outside_rect(poly, x, y, w, h):
    poly = np.array(poly)
    if poly[:, 0].max() < x or poly[:, 0].min() > x + w:
        return True
    if poly[:, 1].max() < y or poly[:, 1].min() > y + h:
        return True
    return False


def split_regions(axis):
    regions = []
    min_axis = 0
    for i in range(1, axis.shape[0]):
        if axis[i] != axis[i - 1] + 1:
            region = axis[min_axis:i]
            min_axis = i
            regions.append(region)
    return regions


def random_select(axis, max_size):
    xx = np.random.choice(axis, size=2)
    xmin = np.min(xx)
    xmax = np.max(xx)
    xmin = np.clip(xmin, 0, max_size - 1)
    xmax = np.clip(xmax, 0, max_size - 1)
    return xmin, xmax


def region_wise_random_select(regions, max_size):
    selected_index = list(np.random.choice(len(regions), 2))
    selected_values = []
    for index in selected_index:
        axis = regions[index]
        xx = int(np.random.choice(axis, size=1))
        selected_values.append(xx)
    xmin = min(selected_values)
    xmax = max(selected_values)
    return xmin, xmax


def crop_area(im, text_polys, min_crop_side_ratio, max_tries):
    h, w, _ = im.shape
    h_array = np.zeros(h, dtype=np.int32)
    w_array = np.zeros(w, dtype=np.int32)
    for points in text_polys:
        points = np.round(points, decimals=0).astype(np.int32)
        minx = np.min(points[:, 0])
        maxx = np.max(points[:, 0])
        w_array[minx:maxx] = 1
        miny = np.min(points[:, 1])
        maxy = np.max(points[:, 1])
        h_array[miny:maxy] = 1
    # ensure the cropped area not across a text
    h_axis = np.where(h_array == 0)[0]
    w_axis = np.where(w_array == 0)[0]

    if len(h_axis) == 0 or len(w_axis) == 0:
        return 0, 0, w, h

    h_regions = split_regions(h_axis)
    w_regions = split_regions(w_axis)

    for i in range(max_tries):
        if len(w_regions) > 1:
            xmin, xmax = region_wise_random_select(w_regions, w)
        else:
            xmin, xmax = random_select(w_axis, w)
        if len(h_regions) > 1:
            ymin, ymax = region_wise_random_select(h_regions, h)
        else:
            ymin, ymax = random_select(h_axis, h)

        if xmax - xmin < min_crop_side_ratio * w or ymax - ymin < min_crop_side_ratio * h:
            # area too small
            continue
        num_poly_in_rect = 0
        for poly in text_polys:
            if not is_poly_outside_rect(poly, xmin, ymin, xmax - xmin,
                                        ymax - ymin):
                num_poly_in_rect += 1
                break

        if num_poly_in_rect > 0:
            return xmin, ymin, xmax - xmin, ymax - ymin

    return 0, 0, w, h


class EastRandomCropData(object):
    def __init__(self,
                 size=(640, 640),
                 max_tries=10,
                 min_crop_side_ratio=0.1,
                 keep_ratio=True,
                 **kwargs):
        self.size = size
        self.max_tries = max_tries
        self.min_crop_side_ratio = min_crop_side_ratio
        self.keep_ratio = keep_ratio

    def __call__(self, data):
        img = data['image']
        text_polys = data['polys']
        ignore_tags = data['ignore_tags']
        texts = data['texts']
        all_care_polys = [
            text_polys[i] for i, tag in enumerate(ignore_tags) if not tag
        ]
        # 计算crop区域
        crop_x, crop_y, crop_w, crop_h = crop_area(
            img, all_care_polys, self.min_crop_side_ratio, self.max_tries)
        # crop 图片 保持比例填充
        scale_w = self.size[0] / crop_w
        scale_h = self.size[1] / crop_h
        scale = min(scale_w, scale_h)
        h = int(crop_h * scale)
        w = int(crop_w * scale)
        if self.keep_ratio:
            padimg = np.zeros((self.size[1], self.size[0], img.shape[2]),
                              img.dtype)
            padimg[:h, :w] = cv2.resize(
                img[crop_y:crop_y + crop_h, crop_x:crop_x + crop_w], (w, h))
            img = padimg
        else:
            img = cv2.resize(
                img[crop_y:crop_y + crop_h, crop_x:crop_x + crop_w],
                tuple(self.size))
        # crop 文本框
        text_polys_crop = []
        ignore_tags_crop = []
        texts_crop = []
        for poly, text, tag in zip(text_polys, texts, ignore_tags):
            poly = ((poly - (crop_x, crop_y)) * scale).tolist()
            if not is_poly_outside_rect(poly, 0, 0, w, h):
                text_polys_crop.append(poly)
                ignore_tags_crop.append(tag)
                texts_crop.append(text)
        data['image'] = img
        data['polys'] = np.array(text_polys_crop)
        data['ignore_tags'] = ignore_tags_crop
        data['texts'] = texts_crop
        return data


class PSERandomCrop(object):
    def __init__(self, size, **kwargs):
        self.size = size

    def __call__(self, data):
        imgs = data['imgs']

        h, w = imgs[0].shape[0:2]
        th, tw = self.size
        if w == tw and h == th:
            return imgs

        # label中存在文本实例，并且按照概率进行裁剪，使用threshold_label_map控制
        if np.max(imgs[2]) > 0 and random.random() > 3 / 8:
            # 文本实例的左上角点
            tl = np.min(np.where(imgs[2] > 0), axis=1) - self.size
            tl[tl < 0] = 0
            # 文本实例的右下角点
            br = np.max(np.where(imgs[2] > 0), axis=1) - self.size
            br[br < 0] = 0
            # 保证选到右下角点时，有足够的距离进行crop
            br[0] = min(br[0], h - th)
            br[1] = min(br[1], w - tw)

            for _ in range(50000):
                i = random.randint(tl[0], br[0])
                j = random.randint(tl[1], br[1])
                # 保证shrink_label_map有文本
                if imgs[1][i:i + th, j:j + tw].sum() <= 0:
                    continue
                else:
                    break
        else:
            i = random.randint(0, h - th)
            j = random.randint(0, w - tw)

        # return i, j, th, tw
        for idx in range(len(imgs)):
            if len(imgs[idx].shape) == 3:
                imgs[idx] = imgs[idx][i:i + th, j:j + tw, :]
            else:
                imgs[idx] = imgs[idx][i:i + th, j:j + tw]
        data['imgs'] = imgs
        return data