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 (ignore Safari, #120 & #509)
    if (image.naturalWidth && !IS_SAFARI) {
      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;

    // Scale should come first before rotate (#633)
    if (isNumber(scaleX) && isNumber(scaleY)) {
      transforms.push('scale(' + scaleX + ',' + scaleY + ')');
    }

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

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

  function getRotatedSizes(data, isReversed) {
    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 (!isReversed) {
      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 dstX = 0;
    var dstY = 0;
    var dstWidth = data.naturalWidth;
    var dstHeight = 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 = dstWidth * abs(scaleX || 1);
    var canvasHeight = dstHeight * abs(scaleY || 1);
    var translateX;
    var translateY;
    var rotated;

    if (scalable) {
      translateX = canvasWidth / 2;
      translateY = canvasHeight / 2;
    }

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

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

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

    if (advanced) {
      dstX = -dstWidth / 2;
      dstY = -dstHeight / 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, floor(dstX), floor(dstY), floor(dstWidth), floor(dstHeight));

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

    return canvas;
  }

  function getTouchesCenter(touches) {
    var length = touches.length;
    var pageX = 0;
    var pageY = 0;

    if (length) {
      $.each(touches, function (i, touch) {
        pageX += touch.pageX;
        pageY += touch.pageY;
      });

      pageX /= length;
      pageY /= length;
    }

    return {
      pageX: pageX,
      pageY: pageY
    };
  }

  function getStringFromCharCode(dataView, start, length) {
    var str = '';
    var i;

    for (i = start, length += start; i < length; i++) {
      str += fromCharCode(dataView.getUint8(i));
    }

    return str;
  }

  function getOrientation(arrayBuffer) {
    var dataView = new DataView(arrayBuffer);
    var length = dataView.byteLength;
    var orientation;
    var exifIDCode;
    var tiffOffset;
    var firstIFDOffset;
    var littleEndian;
    var endianness;
    var app1Start;
    var ifdStart;
    var offset;
    var i;

    // Only handle JPEG image (start by 0xFFD8)
    if (dataView.getUint8(0) === 0xFF && dataView.getUint8(1) === 0xD8) {
      offset = 2;

      while (offset < length) {
        if (dataView.getUint8(offset) === 0xFF && dataView.getUint8(offset + 1) === 0xE1) {
          app1Start = offset;
          break;
        }

        offset++;
      }
    }

    if (app1Start) {
      exifIDCode = app1Start + 4;
      tiffOffset = app1Start + 10;

      if (getStringFromCharCode(dataView, exifIDCode, 4) === 'Exif') {
        endianness = dataView.getUint16(tiffOffset);
        littleEndian = endianness === 0x4949;

        if (littleEndian || endianness === 0x4D4D /* bigEndian */) {
          if (dataView.getUint16(tiffOffset + 2, littleEndian) === 0x002A) {
            firstIFDOffset = dataView.getUint32(tiffOffset + 4, littleEndian);

            if (firstIFDOffset >= 0x00000008) {
              ifdStart = tiffOffset + firstIFDOffset;
            }
          }
        }
      }
    }

    if (ifdStart) {
      length = dataView.getUint16(ifdStart, littleEndian);

      for (i = 0; i < length; i++) {
        offset = ifdStart + i * 12 + 2;

        if (dataView.getUint16(offset, littleEndian) === 0x0112 /* Orientation */) {

          // 8 is the offset of the current tag's value
          offset += 8;

          // Get the original orientation value
          orientation = dataView.getUint16(offset, littleEndian);

          // Override the orientation with its default value for Safari (#120)
          if (IS_SAFARI) {
            dataView.setUint16(offset, 1, littleEndian);
          }

          break;
        }
      }
    }

    return orientation;
  }

  function dataURLToArrayBuffer(dataURL) {
    var base64 = dataURL.replace(REGEXP_DATA_URL_HEAD, '');
    var binary = atob(base64);
    var length = binary.length;
    var arrayBuffer = new ArrayBuffer(length);
    var dataView = new Uint8Array(arrayBuffer);
    var i;

    for (i = 0; i < length; i++) {
      dataView[i] = binary.charCodeAt(i);
    }

    return arrayBuffer;
  }

  // Only available for JPEG image
  function arrayBufferToDataURL(arrayBuffer) {
    var dataView = new Uint8Array(arrayBuffer);
    var length = dataView.length;
    var base64 = '';
    var i;

    for (i = 0; i < length; i++) {
      base64 += fromCharCode(dataView[i]);
    }

    return 'data:image/jpeg;base64,' + btoa(base64);
  }