AWS API Gateway and Lambda to return image
Solution 1
It seems AWS has simplified this process, so that many answers are outdated and/or overly complicated.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<string, string>();
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. <img src="https://asdf.execute-api.us-east-1.amazonaws.com/live/myapi" />
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.
Solution 2
Luckily, now AWS API Gateway supports binary data, though you also need to update your resource method through the CLI as it is not yet implemented in the Console. This is what you need to do:
- In the Method Response of your method
SetContent-Type
asimage/jpeg
in HTTP 200 Status Response Header - In the Integration Response of your method
SetContent-Type
as'image/jpeg'
in Header Mappings. Mind the quotes! - With the AWS CLI, set
contentHandling
attribute toCONVERT_TO_BINARY
on your Integration Response
Check to entire process in this great step-by step guide: https://stackoverflow.com/a/41434295/720665
Solution 3
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
Solution 4
Just to be clear, the client does two different requests:
- The first to get the HTML (including the image url).
- The second to fetch the image data from the url.
In other words, the image data is not inlined in the HTML.
Based on this knowledge you can have a Lambda (behind the API gateway) as you suggest. The Lambda implementation can have some logic that determines the url to the image stored in S3. However, the Lambda returns JSON data and not HTML (there are workarounds such as return the html in a variable) which makes things trickier, especially for large HTML pages.
I suggest a slightly different approach, since just receiving an image tag will not get you far. I assume you will inline the image tag in a HTML document, probably by using JavaScript. Then you might as well let the API Gateway / Lambda request return a JSON document with the image url and let the JavaScript either update an existing image tag with the new url or generate the tag for you.
user1736191
Updated on June 04, 2020Comments
-
user1736191 almost 4 years
Say I have this HTML:
<img src="http://example.com/pic"/>
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!