A simple python module to generate anchor (aka default/prior) boxes for object detection tasks. Calculated anchor boxes are returned as ndarrays in pascal_voc format by default.


pip install pybx


To calculate the anchor boxes for a single feature size and aspect ratio, given the image size:

from pybx import anchor

image_sz = (300, 300, 3)
feature_sz = (10, 10)
asp_ratio = 1/2.

anchor.bx(image_sz, feature_sz, asp_ratio)

To calculate anchor boxes for multiple feature sizes and aspect ratios:

feature_szs = [(10, 10), (8, 8)]
asp_ratios = [1., 1/2., 2.]

anchor.bxs(image_sz, feature_szs, asp_ratios)

More on visualising the anchor boxes .


  • Wrapper class for boxes with vis.draw() method
  • Companion notebook
  • IOU check (return best overlap boxes)
  • Return masks
  • Unit tests
  • Specific tests
    • feature_sz of different aspect ratios
    • image_sz of different aspect ratios
  • Move to


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