How to calculate the area from ndpi file

[苏斐]

Hi Opensliders,

I’m new for OpenSlide. I have some .ndpi files with 400x high resolution from HAMAMATSU scan. I’d like to calculate the area of contour. I get the area of target contour with cv2::contourArea(). How could I convert the value to mm2?

Best wishes,

Fei