将voc格式的数据转为json格式用于detectron的训练

"""
Created on Tue Jun 12 10:24:36 2018
将voc格式转json格式用于caffe2的detectron的训练
在detectron中voc_2007_train.json和voc_2007_val.json中categories的顺序必须保持一致
因此最好事先确定category的顺序，书写在category_set中
@author: yantianwang
"""

import xml.etree.ElementTree as ET
import os
import json
import collections

coco = dict()
coco['images'] = []
coco['type'] = 'instances'
coco['annotations'] = []
coco['categories'] = []

#category_set = dict()
image_set = set()
image_id = 2019000001  #train:2018xxx; val:2019xxx; test:2020xxx
category_item_id = 1
annotation_id = 1
category_set = ['small-vehicle', 'large-vehicle', 'plane','harbor', 'ship', 
             'tennis-court', 'soccer-ball-field', 'ground-track-field',
             'baseball-diamond', 'swimming-pool', 'roundabout', 'basketball-court', 
             'storage-tank', 'bridge', 'helicopter']
'''
def addCatItem(name):
    global category_item_id
    category_item = dict()
    category_item['supercategory'] = 'none'
    category_item_id += 1
    category_item['id'] = category_item_id
    category_item['name'] = name
    coco['categories'].append(category_item)
    category_set[name] = category_item_id
    return category_item_id
'''

def addCatItem(name):
    '''
    增加json格式中的categories部分
    '''
    global category_item_id
    category_item = collections.OrderedDict()
    category_item['supercategory'] = 'none'
    category_item['id'] = category_item_id
    category_item['name'] = name
    coco['categories'].append(category_item)
    category_item_id += 1

def addImgItem(file_name, size):
    global image_id
    if file_name is None:
        raise Exception('Could not find filename tag in xml file.')
    if size['width'] is None:
        raise Exception('Could not find width tag in xml file.')
    if size['height'] is None:
        raise Exception('Could not find height tag in xml file.')
    #image_item = dict()    #按照一定的顺序，这里采用collections.OrderedDict()
    image_item = collections.OrderedDict()
    jpg_name = os.path.splitext(file_name)[0]+'.png'
    image_item['file_name'] = jpg_name  
    image_item['width'] = size['width']   
    image_item['height'] = size['height']
    image_item['id'] = image_id
    coco['images'].append(image_item)
    image_set.add(jpg_name)    
    image_id = image_id+1
    return image_id


def addAnnoItem(object_name, image_id, category_id, bbox):
    global annotation_id
    #annotation_item = dict()
    annotation_item = collections.OrderedDict()
    annotation_item['segmentation'] = []
    seg = []
    # bbox[] is x,y,w,h
    # left_top
    seg.append(bbox[0])
    seg.append(bbox[1])
    # left_bottom
    seg.append(bbox[0])
    seg.append(bbox[1] + bbox[3])
    # right_bottom
    seg.append(bbox[0] + bbox[2])
    seg.append(bbox[1] + bbox[3])
    # right_top
    seg.append(bbox[0] + bbox[2])
    seg.append(bbox[1])
    annotation_item['segmentation'].append(seg)
    annotation_item['area'] = bbox[2] * bbox[3]
    annotation_item['iscrowd'] = 0
    annotation_item['image_id'] = image_id
    annotation_item['bbox'] = bbox
    annotation_item['category_id'] = category_id
    annotation_item['id'] = annotation_id
    annotation_item['ignore'] = 0 
    annotation_id += 1 
    coco['annotations'].append(annotation_item)


def parseXmlFiles(xml_path):
    xmllist = os.listdir(xml_path)
    xmllist.sort()
    for f in xmllist:
        if not f.endswith('.xml'):
            continue

        bndbox = dict()
        size = dict()
        current_image_id = None
        current_category_id = None
        file_name = None
        size['width'] = None
        size['height'] = None
        size['depth'] = None

        xml_file = os.path.join(xml_path, f)
        print(xml_file)

        tree = ET.parse(xml_file)
        root = tree.getroot() #抓根结点元素

        if root.tag != 'annotation': #根节点标签
            raise Exception('pascal voc xml root element should be annotation, rather than {}'.format(root.tag))

        # elem is <folder>, <filename>, <size>, <object>
        for elem in root:
            current_parent = elem.tag
            current_sub = None
            object_name = None

            #elem.tag, elem.attrib，elem.text
            if elem.tag == 'folder':
                continue

            if elem.tag == 'filename':
                file_name = elem.text
                if file_name in category_set:
                    raise Exception('file_name duplicated')

            # add img item only after parse <size> tag
            elif current_image_id is None and file_name is not None and size['width'] is not None:
                if file_name not in image_set:
                    current_image_id = addImgItem(file_name, size)#图片信息
                    print('add image with {} and {}'.format(file_name, size))
                else:
                    raise Exception('duplicated image: {}'.format(file_name))
                    # subelem is <width>, <height>, <depth>, <name>, <bndbox>
            for subelem in elem:
                bndbox['xmin'] = None
                bndbox['xmax'] = None
                bndbox['ymin'] = None
                bndbox['ymax'] = None

                current_sub = subelem.tag
                if current_parent == 'object' and subelem.tag == 'name':
                    object_name = subelem.text
                    #if object_name not in category_set:
                    #    current_category_id = addCatItem(object_name)
                    #else:
                    #current_category_id = category_set[object_name]
                    current_category_id = category_set.index(object_name)+1 #index默认从0开始,但是json文件是从1开始，所以+1
                elif current_parent == 'size':
                    if size[subelem.tag] is not None:
                        raise Exception('xml structure broken at size tag.')
                    size[subelem.tag] = int(subelem.text)

                # option is <xmin>, <ymin>, <xmax>, <ymax>, when subelem is <bndbox>
                for option in subelem:
                    if current_sub == 'bndbox':
                        if bndbox[option.tag] is not None:
                            raise Exception('xml structure corrupted at bndbox tag.')
                        bndbox[option.tag] = int(option.text)

                # only after parse the <object> tag
                if bndbox['xmin'] is not None:
                    if object_name is None:
                        raise Exception('xml structure broken at bndbox tag')
                    if current_image_id is None:
                        raise Exception('xml structure broken at bndbox tag')
                    if current_category_id is None:
                        raise Exception('xml structure broken at bndbox tag')
                    bbox = []
                    # x
                    bbox.append(bndbox['xmin'])
                    # y
                    bbox.append(bndbox['ymin'])
                    # w
                    bbox.append(bndbox['xmax'] - bndbox['xmin'])
                    # h
                    bbox.append(bndbox['ymax'] - bndbox['ymin'])
                    print(
                    'add annotation with {},{},{},{}'.format(object_name, current_image_id-1, current_category_id, bbox))
                    addAnnoItem(object_name, current_image_id-1, current_category_id, bbox)
    #categories部分
    for categoryname in category_set:
        addCatItem(categoryname) 


if __name__ == '__main__':
    xml_path = '/home/yantianwang/clone/VOC2007/val_Annotations'
    json_file = '/home/yantianwang/clone/VOC2007/Annotations/voc_2007_val.json'
    parseXmlFiles(xml_path)
json.dump(coco, open(json_file, 'w'))