使用Node.js中的GraphicsMagick / ImageMagick包在AWS Lambda中将JPG转换为WebP

Question

I am leveraging the AWS Lambda example script to resize a JPG image using Node.js and ImageMagick/GraphicsMagick libraries. I want to make a simple modification to convert the image from a JPG to a WebP format after the resize. (GraphicsMagick does not support WebP, but ImageMagick does, which is subclassed in the script) . This should be possible with the following block of code, as per the example in the Buffers section here (which converts JPG to PNG).

gm('img.jpg')
.resize(100, 100)
.toBuffer('PNG',function (err, buffer) {
  if (err) return handle(err);
  console.log('done!');
})

When I run that block of code in my local Node.js installation (replacing PNG with WebP), it works.

When I modify the transform function (see below) of the AWS Lambda example script , however, and execute it on AWS, I receive the following "Stream yields empty buffer" error:

Unable to resize mybucket/104A0378.jpg and upload to mybucket_resized/resized-104A0378.jpg due to an error: Error: Stream yields empty buffer

Modified transform() function (see the line with 'webp'):

function tranform(response, next) {
            gm(response.Body).size(function(err, size) {
                // Infer the scaling factor to avoid stretching the image unnaturally.
                var scalingFactor = Math.min(
                    MAX_WIDTH / size.width,
                    MAX_HEIGHT / size.height
                );
                var width  = scalingFactor * size.width;
                var height = scalingFactor * size.height;

                // Transform the image buffer in memory.
                this.resize(width, height)
                    .toBuffer('webp', function(err, buffer) {
                        if (err) {
                            next(err);
                        } else {
                            next(null, response.ContentType, buffer);
                        }
                    });
            });
        }

I realize that the response.ContentType is still equal to image/jpeg, but I don't think that is playing a role here. Also, I realize that I should probably convert to WebP before resizing but...baby steps!

Any ideas?

Answer 1

I have encountered the same error, "Stream yields empty buffer", in other operations using gm and AWS lambda.

Turns out that the lambda container ran out of memory.

I tested this assumption using a large image that was constantly throwing an error.

When i increased the memory of the lambda function everything worked perfectly.

Hope this helps you as well

Answer 2

ImageMagick has to be specifically compiled with WebP support. My experimenting seems to show that the ImageMagick on AWS Lambda is not compiled with WEBP :(