1. Problem solving process
In order to implement the target detection model fast_rcnn, prepare to use the coco data set for model training, here you need to import the coco data set and perform data set processing.
import torch
import torchvision
import torch.utils.data
from pycocotools.coco import COCO
def convert_to_coco_api(ds):
coco_ds = COCO()
# annotation IDs need to start at 1, not 0
ann_id = 1
dataset = {
'images': [], 'categories': [], 'annotations': []}
categories = set()
for img_idx in range(len(ds)):
# find better way to get target
hw, targets = ds.coco_index(img_idx)
image_id = targets["image_id"].item()
img_dict = {
}
img_dict['id'] = image_id
img_dict['height'] = hw[0]
img_dict['width'] = hw[1]
dataset['images'].append(img_dict)
bboxes = targets["boxes"]
bboxes[:, 2:] -= bboxes[:, :2]
bboxes = bboxes.tolist()
labels = targets['labels'].tolist()
areas = targets['area'].tolist()
iscrowd = targets['iscrowd'].tolist()
num_objs = len(bboxes)
for i in range(num_objs):
ann = {
}
ann['image_id'] = image_id
ann['bbox'] = bboxes[i]
ann['category_id'] = labels[i]
categories.add(labels[i])
ann['area'] = areas[i]
ann['iscrowd'] = iscrowd[i]
ann['id'] = ann_id
dataset['annotations'].append(ann)
ann_id += 1
dataset['categories'] = [{
'id': i} for i in sorted(categories)]
coco_ds.dataset = dataset
coco_ds.createIndex()
return coco_ds
def get_coco_api_from_dataset(dataset):
for _ in range(10):
if isinstance(dataset, torchvision.datasets.CocoDetection):
break
if isinstance(dataset, torch.utils.data.Subset):
dataset = dataset.dataset
if isinstance(dataset, torchvision.datasets.CocoDetection):
return dataset.coco
return convert_to_coco_api(dataset)
运行出现 
pycocotoolsIt can be concluded that there is no module in the current environment , so it is needed
pip install pycocotools
------报错了-------
Then the query has a way to download from gitee
pip install git+https://gitee.com/pursuit_zhangyu/cocoapi.git#subdirectory=PythonAPI
------报错了-------
If the above error message is found to be a missing Cythonmodule, then download the Cython module
pip install Cython
Then proceed to the previous step
pip install git+https://gitee.com/pursuit_zhangyu/cocoapi.git#subdirectory=PythonAPI
------还是不行-------
Finally, I found that the linux download is the above operation, because I am windous, I should follow the following instructions
pip install pycocotools-windows
成功！！
