Reteurn binary content from lambda through api gateway

Serverless Framework
1

I want to return an image from lambda. AWS API gateway assume that returned content is text and re-encodes it using utf-8, which corrupts response with binary content. There are two writeups, one by AWS and one by Serverless about how to turn this feature off.

https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-payload-encodings.html

However, it does not work. Here’s my serverless.yml

provider:
name: aws
runtime: nodejs12.x
stage: dev
region: us-east-1
memorySize: 128
role: arn:aws:iam::xxxxxxxxxxxx:role/xxxxxxxxxxxxxxxxxx
environment:
ENV_NAME: develop
apiGateway:
binaryMediaTypes:
- ‘image/webp’
- ‘/’

The browser asks for image/webp and I return and image file with content type image/webp. Still the API gateway tries to encode it as utf-8, adding bytes infront
of some other bytes. I also tried to remove ‘image/webp’ from serverless.yml leaving only ‘/’, but it did not help.

After deploying using npm run deploy-develop this is how it looks in AWS console

/myserverless
/ui
/{proxy+}
GET Lambda 1.0 (explicit response format)

2

If anyone is having this issue, in addition to declaring the binaryMediaTypes in yml files, the lambda response must also contain a header with same content-type, the body in base64 format and isBase64Encoded: true;
e.g.

{
  statusCode: 200,
  headers: {
    'Content-Type': 'image/png'
  },
  body: result.Body.toString('base64'),
  isBase64Encoded: true
};