Before using this module, you should already understand API Gateway and AWS Lambda. Specifically, you must be using Proxy Integration.
Starting with v1.5.0, serverless-http supports API Gateway binary modes. Binary support will base64 decode the incoming request body - when API Gateway specifies that it is encoded - and will base64 encode a response body if the Content-Type or Content-Encoding matches a known binary type/encoding. This means you can gzip your JSON or return a raw image, but it requires advanced configuration within API Gateway and is generally not fun to work with (consider yourself warned!)
Existing serverless-http APIs (i.e. those that return JSON as text) should not be affected. See advanced configuration documentation for details.