I CAN SOLVE YOUR CHINA POST PROJECT
Hello,
Professional web developer here.
I would like to implement your API labels functionality. I have a lot of API experience and I can read Chinese.
I am planning to do this by the standard API calls and response, like you said, its classical API interaction. Then, once I receive data from China Post about the label, I would automatically generate and save a custom image or PDF (as you wish) that you can print.
I invite you to a further discussion.
Thank you!