achieve parity with the official implementation

[marius10p]

This requires matching the AP scores at IoUs of 0.5, 0.75 and 0.9 on the Cellpose test data, using the known diameter for each image (or the built-in diameter estimation from Cellpose).

[yxdragon]

hi, what is AP scores at IoUs of 0.5, 0.75 and 0.9 ? a standard dataset?
I just use the cellpose.org website's demo image do some test. and the result looks ok. but I did not test on other dataset.
I implements a area estimation method (3 sigma filter). but only works well when there are many cells and in the similar size.