Translate a crop area from a zoomed copy

scale-crop.js

// Usage:
// node scale-crop.js infile zoom translate_x translate_y rotation outfile

'use strict';

var gm = require('gm');
var args = process.argv.slice(2);
console.log(args);

var infile = args[0];
var outfile = args[5];

var offset = 10;
var finalHeight = 720;

var zoom = args[1];
var translate_x = args[2];
var translate_y = args[3];
var rotation = args[4];

gm(infile).size(function (err, size){
  if (err){
    console.error(err);
  } else {
    var coeff = size.width / size.height;
    var finalWidth = finalHeight * coeff;
    var crop_w = size.width - (2 * (size.width / offset));
    var crop_h = size.height - (2 * (size.height / offset));
    var crop_x = (size.width / 2) - (crop_w / 2) + translate_x;
    var crop_y = (size.height / 2) - (crop_h / 2) + translate_y;

    gm(infile)
      .scale(size.width * zoom)
      .rotate('black', rotation)
      .crop(crop_w, crop_h, crop_x, crop_y)
      .resize(finalWidth, finalHeight)
      .write(outfile, function (err){
        if (err){
          console.error(err);
        } else {
          console.log('Success!');
        }
      });
  }
});