Rich Media Card Source Image For Cropping

What is the perfect size for the header images on rich media card images?

Problem

WeChat automatically crops your images which sometimes cuts out parts you would like to be visible

Solution

For header images on Rich Media Messages the format allowing visible images on iOS, Android and BlackBerry that are not obscured by the headers text, use the following dimensions:
Main image size: 820px wide by 270px high
Additional padding: add 70 px white padding to the top of the image and 160 px white padding to the bottom of the image