AWS API Gateway and Lambda to return image

Question

Say I have this HTML:

What I would like to do is have example.com/pic map to an AWS API Gateway endpoint.

That endpoint would then call a lambda function.

That lambda function would read a random image from an s3 bucket and return it.

So my aim is to use a STANDARD HTML image tag and end up with an image from an s3 bucket but going via some decision code in the lambda to decide the image to return.

I know you can use s3 to serve static content directly (hence the lambda to make the decision about what image). I also know I could do stuff in the lambda like b64 encode the response and then handle it on the client but I am aiming to use the standard HTML IMG tag.

Is this possible?

I've tried using the ResponseStreamHandler (Java SDK) for the lambda and returning the byte array of the image and also added the API gateway config to not map the output to JSON, but nothing seems to work!

user_1145177 · Answer

It seems AWS has simplified this process, so that many answers are outdated and/or overly complicated.

This is how I got Lambda to return an image through the API Gateway, as of June 2018:

1) In API Gateway, enable Use Lambda Proxy integration for your API. (This setting is located on the Integration Request section, where you had set the type to Lambda.)

2) In API Gateway, select your API and click Settings. In Binary Media Types add */*. (Note: I tried adding simply 'image/jpeg', but it seems to require */* to get all of this to work)

3) Be sure to deploy your API, otherwise your changes will not be live. (In API Gateway, select your API, then Actions > Deploy API).

4) In your Lambda code, return your image in Base64 encoding (this example is C# code):

    // set the Content-type header
    // set to whichever image type you're returning
    var headersDic = new Dictionary();
    headersDic.Add("Content-type", "image/jpeg");

    // return the response object that APIGateway requires
    return new APIGatewayProxyResponse
    {
        StatusCode = 200,
        Headers = headersDic,
        // return the image in Base64 encoding
        Body = Convert.ToBase64String(...your image data...),
        IsBase64Encoded = true
    };

Done.

If you've setup your API to not require authentication, simply type your API link into your browser, and it will display the image. Or put the API link into an IMG tag. e.g.

Note: Even though in step 2 you set the Binary Media Types to */*, API Gateway will still return text if that is what your Lambda is returning.

user_620324 · Answer

I've run in to a similar problem. As mentioned you currently can't directly return your image in binary format from your API Gateway endpoint, which would be required for the browser to display it correctly.

However, I solved this by instead having API Gateway return a 302 Redirect, pointing to the correct file in S3. You can have your Lambda function return the url to the file, which is later on mapped to the Location header in API Gateway. The browser will follow the redirect and display the image properly.

There are several ways to implement the redirect, but I did as follow:

Lambda returns an object with the target image like so:

function handler(event, context) {
     context.succeed({ 
         location: "https://[bucket-name].s3-eu-west-1.amazonaws.com/myimage.png" });
     });
}

Remove the normal '200' Method Response Status from The Integration Response in API Gateway. Replace it with a '302' response status and add the 'Location' header mapped to value 'integration.response.body.location'
Add the 302 status to the Method Response as well

AWS API Gateway and Lambda to return image

5 Answers