AP, Map value calculation

AP: All pictures a certain class

Map: Average of all images for all classes of APS

With a score threshold, all boxes greater than score are assumed to be correctly output for all predictions, match these boxes to GT (IOU is larger than a certain threshold is considered to be successful), get auccracy and recall under current score, Different score obtain different auccracy and recall, so that a curve is obtained, and the area of this curve and x and Y coordinate integrals is the ultimate AP.

Auccracy calculation: The number of boxes that successfully match the GT/the number of boxes larger than score (all boxes greater than score are the actual predictive output of the detector)

Recall calculation: Number of boxes for successful matching GT/all GT boxes

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AP, Map value calculation