目标检测：SSD.Pytorch 运行发生的错误

SSD模型：https://github.com/amdegroot/ssd.pytorch 

1、RuntimeError: Legacy autograd function with non-static forward method is deprecated

原因：当前的pytorch版本过高，而原代码的版本较低。如果pytorch版本高于1.3会出现该问题。当前版本要求forward过程是静态的，所以需要将原代码进行修改。

解决方法：参考1替换的代码文件地址 Github 镜像仓库 源项目地址 ⬇ ⬇https://gitcode.net/mirrors/sayakbanerjee1999/Single-Shot-Object-Detection-Updated?utm_source=csdn_github_accelerator

2、使用自己的数据集进行训练

如何使用自己的数据集进行训练：参考2 参考3

2.1 RuntimeError: shape '[-1, 21]' is invalid for input of size 52392

修改ssd.py中的代码forward方法红色框中的【21】改为【self.num_classes】：（PS:该ssd.py代码为问题1中解决后修改的ssd.py）

 2.2 运行test.py 或者 eval.py 时报错：IndexError: too many indices for array

原因：annotation也就是xml文件里面有些包含空目标

解决：使用下述代码，检查哪些xml没有标注目标，然后重新打标签

import argparse
import sys
import cv2
import os

import os.path          as osp
import numpy            as np

if sys.version_info[0] == 2:
    import xml.etree.cElementTree as ET
else:
    import xml.etree.ElementTree  as ET


parser = argparse.ArgumentParser(
            description='Single Shot MultiBox Detector Training With Pytorch')
train_set = parser.add_mutually_exclusive_group()

parser.add_argument('--root', default=os.path.join(get_dataset_path(), "VOCdevkit", "VOC2021"), help='Dataset root directory path')

args = parser.parse_args()

CLASSES = (  # always index 0
    'thrips', 'scarab_beetles', 'red_spiders', 'spodoptera_litura_fabricius',
    'epicauta_ruficeps')

annopath = osp.join('%s', 'Annotations', '%s.{}'.format("xml"))
imgpath  = osp.join('%s', 'JPEGImages',  '%s.{}'.format("jpg"))

problem = []
def voc_checker(image_id, width, height, keep_difficult=False):
    """
    检查是否有xml没有标注目标
    Args:
        image_id:
        width:
        height:
        keep_difficult:

    Returns:

    """
    target = ET.parse(annopath % image_id).getroot()
    res = []
    for obj in target.iter('object'):
        difficult = int(obj.find('difficult').text) == 1
        if not keep_difficult and difficult:
            continue
        name = obj.find('name').text.lower().strip()
        bbox = obj.find('bndbox')
        pts = ['xmin', 'ymin', 'xmax', 'ymax']
        bndbox = []
        for i, pt in enumerate(pts):

            cur_pt = int(bbox.find(pt).text) - 1
            # scale height or width
            cur_pt = float(cur_pt) / width if i % 2 == 0 else float(cur_pt) / height

            bndbox.append(cur_pt)

        print("name:{}".format(name))
        label_idx = dict(zip(CLASSES, range(len(CLASSES))))[name]
        bndbox.append(label_idx)
        res += [bndbox]  # [xmin, ymin, xmax, ymax, label_ind]
        # img_id = target.find('filename').text[:-4]
    print("res:{}".format(res))
    try:
        print(np.array(res)[:,4])
        print(np.array(res)[:,:4])
    except IndexError:
        problem.append(image_id)
        print("\nINDEX ERROR HERE !\n")
        # exit(0)
    return res  # [[xmin, ymin, xmax, ymax, label_ind], ... ]

if __name__ == '__main__':
    i = 0
    for name in sorted(os.listdir(osp.join(args.root, 'Annotations'))):
    # as we have only one annotations file per image
        i += 1
        img = cv2.imread(imgpath % (args.root, name.split('.')[0]))
        height, width, channels = img.shape
        print("path : {}".format(annopath % (args.root,name.split('.')[0])))
        res = voc_checker((args.root, name.split('.')[0]), height, width)
    print("Total of annotations : {}".format(i))
    print(problem)

2.3 运行test.py或eval.py时报错：R = [obj for obj in recs[imagename] if obj['name'] == classname]  KeyError: '000133' （000133为图片的名字）

解决：在/data/VOCdevkit/annotations_cache/ 中删掉annots.pkl