function isNumber(n) {
    return typeof n === 'number' && !isNaN(n);
  }

  function isUndefined(n) {
    return typeof n === 'undefined';
  }

  function toArray(obj, offset) {
    var args = [];

    // This is necessary for IE8
    if (isNumber(offset)) {
      args.push(offset);
    }

    return args.slice.apply(obj, args);
  }

  // Custom proxy to avoid jQuery's guid
  function proxy(fn, context) {
    var args = toArray(arguments, 2);

    return function () {
      return fn.apply(context, args.concat(toArray(arguments)));
    };
  }

  function isCrossOriginURL(url) {
    var parts = url.match(/^(https?:)\/\/([^\:\/\?#]+):?(\d*)/i);

    return parts && (
      parts[1] !== location.protocol ||
      parts[2] !== location.hostname ||
      parts[3] !== location.port
    );
  }

  function addTimestamp(url) {
    var timestamp = 'timestamp=' + (new Date()).getTime();

    return (url + (url.indexOf('?') === -1 ? '?' : '&') + timestamp);
  }

  function getCrossOrigin(crossOrigin) {
    return crossOrigin ? ' crossOrigin="' + crossOrigin + '"' : '';
  }

  function getImageSize(image, callback) {
    var newImage;

    // Modern browsers
    if (image.naturalWidth) {
      return callback(image.naturalWidth, image.naturalHeight);
    }

    // IE8: Don't use `new Image()` here (#319)
    newImage = document.createElement('img');

    newImage.onload = function () {
      callback(this.width, this.height);
    };

    newImage.src = image.src;
  }

  function getTransform(options) {
    var transforms = [];
    var rotate = options.rotate;
    var scaleX = options.scaleX;
    var scaleY = options.scaleY;

    if (isNumber(rotate)) {
      transforms.push('rotate(' + rotate + 'deg)');
    }

    if (isNumber(scaleX) && isNumber(scaleY)) {
      transforms.push('scale(' + scaleX + ',' + scaleY + ')');
    }

    return transforms.length ? transforms.join(' ') : 'none';
  }

  function getRotatedSizes(data, reverse) {
    var deg = abs(data.degree) % 180;
    var arc = (deg > 90 ? (180 - deg) : deg) * Math.PI / 180;
    var sinArc = sin(arc);
    var cosArc = cos(arc);
    var width = data.width;
    var height = data.height;
    var aspectRatio = data.aspectRatio;
    var newWidth;
    var newHeight;

    if (!reverse) {
      newWidth = width * cosArc + height * sinArc;
      newHeight = width * sinArc + height * cosArc;
    } else {
      newWidth = width / (cosArc + sinArc / aspectRatio);
      newHeight = newWidth / aspectRatio;
    }

    return {
      width: newWidth,
      height: newHeight
    };
  }

  function getSourceCanvas(image, data) {
    var canvas = $('<canvas>')[0];
    var context = canvas.getContext('2d');
    var x = 0;
    var y = 0;
    var width = data.naturalWidth;
    var height = data.naturalHeight;
    var rotate = data.rotate;
    var scaleX = data.scaleX;
    var scaleY = data.scaleY;
    var scalable = isNumber(scaleX) && isNumber(scaleY) && (scaleX !== 1 || scaleY !== 1);
    var rotatable = isNumber(rotate) && rotate !== 0;
    var advanced = rotatable || scalable;
    var canvasWidth = width;
    var canvasHeight = height;
    var translateX;
    var translateY;
    var rotated;

    if (scalable) {
      translateX = width / 2;
      translateY = height / 2;
    }

    if (rotatable) {
      rotated = getRotatedSizes({
        width: width,
        height: height,
        degree: rotate
      });

      canvasWidth = rotated.width;
      canvasHeight = rotated.height;
      translateX = rotated.width / 2;
      translateY = rotated.height / 2;
    }

    canvas.width = canvasWidth;
    canvas.height = canvasHeight;

    if (advanced) {
      x = -width / 2;
      y = -height / 2;

      context.save();
      context.translate(translateX, translateY);
    }

    if (rotatable) {
      context.rotate(rotate * Math.PI / 180);
    }

    // Should call `scale` after rotated
    if (scalable) {
      context.scale(scaleX, scaleY);
    }

    context.drawImage(image, x, y, width, height);

    if (advanced) {
      context.restore();
    }

    return canvas;
  }