Building you first Serverless app in Node.js with AWS Lambda + S3 + API Gateway

serverless-app-3.js

const im = require('imagemagick');
const fs = require('fs');

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

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

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

const performConvert = (params) => {
  return new Promise(function (res, rej) {
    im.convert(params, (err) => {
      if (err) {
        console.log(`Error${err}`);
        rej(err);
      } else {
        res('operation completed successfully');
      }
    });
  });
}