index.js

const im = require('imagemagick');
const fs = require('fs');
const AWS = require('aws-sdk');
const s3 = new AWS.S3();

exports.handler = async (event) => {
  const operation = event.queryStringParameters ? event.queryStringParameters.operation : null;
  let data = JSON.parse(event.body);
  
  switch (operation) {
    case 'ping':
      sendRes(200, 'pong');
      break;
    case 'convert':
      return await operate(data);
    default:
      return sendRes(401, `Unrecognized operation ${operation}`);
  }
};

const sendRes = (status, body) => {
  return {
    statusCode: status,
    headers: {
        "Content-type": "text/html"
    },
    body: body
  };
}

const operate = async (data) => {
  const customArgs = data.customArgs.split(',') || [];
  let outputExtension = 'png';
  let inputFile = null, outputFile = null;
  
  try {
    if (data.base64Image) {
      inputFile = '/tmp/inputFile.png';
      const buffer = new Buffer(data.base64Image, 'base64');
      fs.writeFileSync(inputFile, buffer);
      customArgs.unshift(inputFile);
    }
    
    outputFile = `/tmp/outputFile.${outputExtension}`;
    customArgs.push(outputFile);
      
    await performConvert(customArgs);
    let fileBuffer = new Buffer(fs.readFileSync(outputFile));
    fs.unlinkSync(outputFile);
      
    await saveFile(fileBuffer);
    return sendRes(200, `<img src="data:image/png;base64,${fileBuffer.toString('base64')}"/>`);
  } catch (error) {
    return sendRes(500, error);
  }
}

const performConvert = (params) => {
  return new Promise((resolve, reject) => {
    im.convert(params, (error) => {
      if (error) {
        reject(error);
      } else {
        resolve('Operation completed succesfully');
      }
    })
  });
}

const saveFile = async (buffer) => {
  const params = {
    Bucket: 'imagetransformation',
    Key: `images/${Date.now().toString()}.png`,
    Body: buffer
  };
  
  return await s3.putObject(params).promise();
}