基于detectron2的语义分割

Question

我使用Detectron2来训练一个使用实例分割的自定义模型，并且工作得很好。在google上有几个使用实例分割的Detectron2教程，但是没有关于语义分割的内容。因此，为了训练自定义实例分割，基于colab (https://colab.research.google.com/drive/16jcaJoc6bCFAQ96jDe2HwtXj7BMD_-m5#scrollTo=7unkuuiqLdqd)的代码是：

from detectron2.engine import DefaultTrainer

cfg = get_cfg()
cfg.merge_from_file(model_zoo.get_config_file("COCO-InstanceSegmentation/mask_rcnn_R_50_FPN_3x.yaml"))
cfg.DATASETS.TRAIN = ("balloon_train",)
cfg.DATASETS.TEST = ()
cfg.DATALOADER.NUM_WORKERS = 2
cfg.MODEL.WEIGHTS = model_zoo.get_checkpoint_url("COCO-InstanceSegmentation/mask_rcnn_R_50_FPN_3x.yaml")  # Let training initialize from model zoo
cfg.SOLVER.IMS_PER_BATCH = 2
cfg.SOLVER.BASE_LR = 0.00025  # pick a good LR
cfg.SOLVER.MAX_ITER = 300    # 300 iterations seems good enough for this toy dataset; you will need to train longer for a practical dataset
cfg.SOLVER.STEPS = []        # do not decay learning rate
cfg.MODEL.ROI_HEADS.BATCH_SIZE_PER_IMAGE = 128   # faster, and good enough for this toy dataset (default: 512)
cfg.MODEL.ROI_HEADS.NUM_CLASSES = 1  # only has one class (ballon). (see https://detectron2.readthedocs.io/tutorials/datasets.html#update-the-config-for-new-datasets)
# NOTE: this config means the number of classes, but a few popular unofficial tutorials incorrect uses num_classes+1 here.

os.makedirs(cfg.OUTPUT_DIR, exist_ok=True)
trainer = DefaultTrainer(cfg) 
trainer.resume_or_load(resume=False)
trainer.train()

为了运行语义分割训练，我将"COCO-InstanceSegmentation/mask_rcnn_R_50_FPN_3x.yaml"替换为"/Misc/semantic_R_50_FPN_1x.yaml"，基本改变了预训练模型，仅此而已。我得到了一个错误：

TypeError: cross_entropy_loss(): argument 'target' (position 2) must be Tensor, not NoneType

我是如何在Google上建立语义分割的？

Answer 1

为了训练语义分割，您可以使用相同的COCO-InstanceSegmentation/mask_rcnn_R_50_FPN_3x.yaml模型。你没必要改变这句话。

您在问题中显示的培训代码是正确的，也可以用于语义分割。所有的改变都是标签文件。

一旦对模型进行了训练，您就可以通过从经过训练的模型加载模型权重来使用它进行推理。

cfg = get_cfg()
cfg.merge_from_file(model_zoo.get_config_file("COCO-InstanceSegmentation/mask_rcnn_R_50_FPN_3x.yaml"))
cfg.MODEL.WEIGHTS = os.path.join(cfg.OUTPUT_DIR, "model_final.pth")
cfg.MODEL.ROI_HEADS.SCORE_THRESH_TEST = 0.5   # set the testing threshold for this model
cfg.DATASETS.TEST = ("Detectron_terfspot_" + "test", )                      # the name given to your dataset when loading/registering it
cfg.DATALOADER.NUM_WORKERS = 2
cfg.SOLVER.IMS_PER_BATCH = 2
cfg.MODEL.ROI_HEADS.NUM_CLASSES = 1
predictor = DefaultPredictor(cfg)