Support Dynamic Area Threshold in Datasets

[jbwang1997]

This issue describes the development requirement of a feature we wish to collaborate with the community. In this issue, we welcome the community developers to participate in the development of the dynamic area threshold.

Description

For now, mmdetection filters instances whose areas are less than 32. It's better to change an integer threshold for annotations filtering to a float ratio threshold based on annotation_area to image_area ratio.

Steps

• Implement the feature
• Add unit tests to test your code

Resources

• Related Issue: Filter annotations in dataset by an (annotation_area / image_area) ratio threshold  #6826
• Code of filtering function:

  mmdetection/mmdet/datasets/coco.py

  Line 99 in 83eea4b

  def _filter_imgs(self, min_size=32):

Reviewers

@jbwang1997