Object Detection in Detectron2

The details

Here is a list of the parameters that you can try to play around with in Detectron2.

Process

  1. Region Proposal Network (RPN): The RPN is responsible for generating object proposals in an image. It takes an image as input and outputs a set of bounding box proposals, along with their objectness scores. These proposals serve as potential regions of interest (ROIs) for further processing.

    • MODEL.RPN.PRE_NMS_TOPK_TRAIN: The RPN proposals are ranked based on their objectness scores. This configuration option determines the number of top-scoring RPN proposals to keep before applying non-maximum suppression (NMS) during training. It limits the number of proposals to reduce computational overhead.

    • MODEL.RPN.NMS_THRESH: This option sets the IoU (Intersection over Union) threshold for NMS during training. Proposals with IoU higher than this threshold are considered redundant and suppressed, keeping only the highest-scoring proposal.

  2. ROI Heads: The ROI Heads module takes the region proposals generated by the RPN and performs object classification and bounding box regression on these proposals to obtain the final predictions.

    • MODEL.ROI_HEADS.IOU_THRESHOLDS: This configuration option specifies a list of IoU thresholds to assign ground-truth labels to the region proposals during training. For example, if the IoU threshold is set to 0.5, any proposal with an IoU greater than or equal to 0.5 with a ground-truth box will be labeled as a positive sample.

    • MODEL.ROI_HEADS.NMS_THRESH_TEST: After classification and bounding box regression, NMS is applied to the predicted boxes to remove redundant detections during testing. This option sets the IoU threshold for NMS during inference.

    • MODEL.ROI_HEADS.SCORE_THRESH_TEST: This option sets the minimum confidence score threshold for retaining detections during inference. Detections with scores lower than this threshold are discarded as false positives.

For more implementation details, check out this awesome guide.

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