How can I transfer uint8 to ascii?

You’re going to want to jpeg compress and image before sending it over any serial port to save bandwidth. Anyway… um, the image is a binary object. You can iterate over it in python and turn each byte into ASCII manually. With a for loop.

Thank you ! But I want to know How to count the pixel one by one??
(I’m a noob on python …any tips for me??)

Use find_blobs. Please read the docs on it: image — machine vision — MicroPython 1.15 documentation