Creating a GIF from remote stream in graphicsmagick - node.js

Question

I am creating a GIF from remote files in node currently by downloading each image to the file system into a tmp folder.
I want to bypass saving the image to a tmp folder and save in memory instead. Is this possible?
As you can see, I have a download function in my AWS class which saves to a tmp folder:
download(key){
return new Promise((resolve, reject) => {
request.head(`${this.base_url}/${this.bucket}/${key}`, (err, res, body) => {
request(`${this.base_url}/${this.bucket}/${key}`)
.pipe(fs.createWriteStream(`tmp/${key}`)).on('close', resolve )
})
})
};
Once they have all downloaded, I have a createGif function in my GifService class which adds each file path as a custom argument of gm, adds a delay of 50ms, resizes then outputs as buffer which I am then uploading to AWS s3.
import gm from 'gm';
...
constructor(){
this.gm = gm()
}
generateGif(images, prefix){
return new Promise((resolve, reject) => {
// for each image we want in array, we pass to gm
images.forEach(image => {
this.gm.in(`tmp/${image.Key}`)
})
// Now we create the gif with 50sec delay between images, sized to 600px x 2
this.gm
.delay(50)
.resize(600,600)
.toBuffer('gif', async (err, buffer) => {
if (err) reject(err)
const params = {
ACL: 'public-read',
Bucket: config.aws_bucket,
ContentType: 'image/gif',
Key: `${prefix}/${uuid()}.gif`,
Body: buffer
}
try{
// uplaod to S3
const upload = await this.aws.upload(params)
// resolve s3 URL
resolve(upload)
}catch(err) {
console.log('err', err)
reject(err)
}
});
})
}
Ideally if I could pass a remote file stream as custom argument, or pass a buffer in as a custom argument as opposed to how I am currently passing in the tmp file path:
images.forEach(image => {
this.gm.in(`tmp/${image.Key}`)
})

Answer 1

I managed to make it work using only streams by converting first the images to miff and concat them into a single stream. Then passing the buffer or the stream into gm again with delay does the trick.
You will need to instal concat-stream npm for this to work.
Sorry for the mixed ES5 code.
import gm from 'gm';
var concat = require('concat-stream');
...
constructor() {
this.gm = gm()
}
start() {
return getYourReadAbleStreamsSomehow().then(streams => {
return generateGif(streams);
}).then(gifBuffer => {
return uploadToAWS(gifBuffer, prefix);
}).catch(err => {
console.log(err)
})
}
uploadToAWS(buffer, prefix) {
const params = {
ACL: 'public-read',
Bucket: config.aws_bucket,
ContentType: 'image/gif',
Key: `${prefix}/${uuid()}.gif`,
Body: buffer
}
try {
// uplaod to S3
const upload = await this.aws.upload(params)
// resolve s3 URL
resolve(upload)
} catch (err) {
console.log('err', err)
reject(err)
}
}
generateGif(imageStreams, delay) {
return new Promise((resolve, reject) => {
var write = concat(function(buffer) {
gm(buffer)
.delay(delay)
.toBuffer('gif', function(err, buffer) {
if (err)
reject(err);
resolve(buffer);
})
})
//Convert to miff and concat streams
var i = 0;
var streamHandler = function() {
gm(imageStreams[i])
.resize('600', '600')
.stream('miff', function(err, stdout, stderr) {
if (err)
reject(err)
var lastOne = i === streams.length - 1;
if (!lastOne)
stdout.once('end', streamHandler)
stdout.pipe(write, {
end: lastOne
});
i++;
});
}
streamHandler();
})
}