AWS code example to slice image

gistfile1.txt

'use strict';

console.log('Loading function');
const aws = require('aws-sdk');
const s3 = new aws.S3({ apiVersion: '2006-03-01' });

var async = require('async');
//http://aheckmann.github.io/gm/docs.html
var gm = require('gm').subClass({ imageMagick: true }); // Enable ImageMagick integration.
var util = require('util');

exports.handler = (event, context, callback) => {

	// Get the object from the event and show its content type
	const bucketName = event.Records[0].s3.bucket.name;
	const keyName = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
	const paramsOrigin = {
		Bucket: bucketName,
		Key: keyName,
	};

	var typeMatch = keyName.match(/\.([^.]*)$/);
	var imageType = typeMatch[1]; //"jpg"

	if (!typeMatch) {
		callback("Could not determine the image type.");
		return;
	}

	async.waterfall([

		function download(next) {
			// Download the image from S3 into a buffer.
			s3.getObject(paramsOrigin, next);
		},

		function resize(response, next) { //if you need resize your image
			
			gm(response.Body).size(function(err,size) {
				
				if(err) {
					next('Error getting size of image');
				}
				
				if(size.width != 4096 ) {
					
					this.resize(4096, 2048, "!").toBuffer(imageType, function(err, buffer) {
                  if (err) {
                  	next('Error resizing image');
                  } else {
                  	next(null, response.ContentType, buffer,{
                  		width: 4096,
                  		height: 2048
                  	});
                  }
            	});
						
				} else {

					next(	null, response.ContentType,response.Body,{
            		width: 4096,
            		height: 2048
            	});
				}
				
			});
			

		},
		function slice (contentType, data,imgDimension, next) {
   		
			var allPromises = [];
			//example tiles to slice
   		var positions = [
   			[0,0],
   			[256,0],
   			[512,0],
			];
			
			function getPromiseCrop(id,positionX,positionY,imageData) {
				return new Promise(function (resolve, reject){
   				
   				gm(imageData).crop(256, 256,positionX,positionY)
		   		.toBuffer(imageType, function(err, buffer) {
		         	
		         	if (err) {
		         		reject('error promise');
		            	next(err);
		         	} else {
		         		console.log('promise done' + id);
		         		
		         		s3.putObject({
							 	Bucket: bucketName,
							 	Key: 'lambda_output/' + id + '.jpg',
							 	Body: buffer,
							 	ContentType: contentType
							},function(){
								resolve();	
							});
							
		         	}
		         });	
   				
   			});
			}
			
   		for (var y = 0; y < positions.length; y++) {
   			var currentPromise = getPromiseCrop(y,positions[y][0],positions[y][1],data);
   			allPromises.push(currentPromise);
   		}
   		
   		
   		Promise.all(allPromises).then(function(values) {      		
      		next(	null,'done all promises');
			},function(error){
				console.log(error);
			});
      	
		},
		function upload(msg,next) {			
			next(	null,msg);
		}

	], function (err) {

		if (err) {			
			callback(null, err);
		} else {
			callback(null, 'Successfully sliced');
		}
		
	});

	
};

This code example was triggered by the put on a bucket