Imagemagick/Shell/child-process NodeJS

Question

I can't seem to get Node to understand my Imagemagick convert command. It works fine in the terminal, I've tried a ton of different permutations for escaping characters but it still reads every seperate string value in my args array as an attempt to convert an image:

convert \ input.jpg \ -write mpr:XY \ +delete \ -respect-parentheses \ \( mpr:XY -resize x640 -sampling-factor 4:2:0 -strip -interlace Plane +write output-640.jpg \) \ \( mpr:XY -resize x320 -sampling-factor 4:2:0 -strip -interlace Plane +write output-320.jpg \) \ \( mpr:XY -resize x155 -sampling-factor 4:2:0 -strip -interlace Plane +write output-155.jpg \) \ \( mpr:XY -resize x45 -sampling-factor 4:2:0 -strip -interlace Plane +write output-45.jpg \) \ null:

This ran in a shell works fine. This code however, fails totally

// const spawn = require('child-process-promise').spawn;
var spawn = require('child_process').spawn;

function argsForSize(number) {
  return [
    '\\(',
    'mpr:XY',
    '-resize',
    'x' + number, 
    '-sampling-factor', 
    '4:2:0', 
    '-strip', 
    '-interlace', 
    'Plane', 
    '+write', 
    'output-' + number +'.jpg', 
    '\\)\\'
  ]
}

let inputPath = '/Users/xconanm/Desktop/imagemagick/test-app/input.jpg';

var args = [
  inputPath, '\\',
  '-write', 'mpr:XY', '\\',       // resize width to 640
  '+delete', '\\',      
  '-respect-parentheses', '\\'
];
let extraArgs = argsForSize(640).concat(argsForSize(320)).concat(argsForSize(155)).concat(argsForSize(55));

extraArgs.push('null:');

args = args.concat(extraArgs)

let child = spawn('convert', args)
console.log(args);

child.stdout.on('data', function(data) {
  console.log('stdout: ' + data);
  //Here is where the output goes
});
child.stderr.on('data', function(data) {
  console.log('stderr: ' + data);
  //Here is where the error output goes
});
child.on('close', function(code) {
  console.log('closing code: ' + code);
  //Here you can get the exit code of the script
});

Answer 1

Got it.... Probably inefficient but :shrug

// const spawn = require('child-process-promise').spawn;
var spawn = require('child_process').spawn;

function argsForSize(number) {
  return [
    '-write', 
    'mpr:XY', 
    '+delete',
    '-respect-parentheses',
    'mpr:XY',
    '-resize',
    'x' + number, 
    '-sampling-factor', 
    '4:2:0', 
    '-strip', 
    '-interlace', 
    'Plane', 
    '-write', 
    'output-' + number +'.jpg'
  ]
}

let inputPath = '/Users/xconanm/Desktop/imagemagick/test-app/input.jpg';

var args = [
  inputPath
];
let extraArgs = argsForSize(640).concat(argsForSize(320)).concat(argsForSize(155)).concat(argsForSize(55));

extraArgs.push('null:');

args = args.concat(extraArgs)

let child = spawn('convert', args)
console.log(args);

child.stdout.on('data', function(data) {
  console.log('stdout: ' + data);
  //Here is where the output goes
});
child.stderr.on('data', function(data) {
  console.log('stderr: ' + data);
  //Here is where the error output goes
});
child.on('close', function(code) {
  console.log('closing code: ' + code);
  //Here you can get the exit code of the script
  process.exit();
});