code: function getJpegSizeFromBytes(data) {
      var hdr = data[0] << 8 | data[1];
      if (hdr !== 0xFFD8) throw new Error('Supplied data is not a JPEG');
      var len = data.length,
          block = (data[4] << 8) + data[5],
          pos = 4,
          bytes,
          width,
          height,
          numcomponents;
  
      while (pos < len) {
        pos += block;
        bytes = readBytes(data, pos);
        block = (bytes[2] << 8) + bytes[3];
  
        if ((bytes[1] === 0xC0 || bytes[1] === 0xC2) && bytes[0] === 0xFF && block > 7) {
          bytes = readBytes(data, pos + 5);
          width = (bytes[2] << 8) + bytes[3];
          height = (bytes[0] << 8) + bytes[1];
          numcomponents = bytes[4];
          return {
            width: width,
            height: height,
            numcomponents: numcomponents
          };
        }
  
        pos += 2;
      }
  
      throw new Error('getJpegSizeFromBytes could not find the size of the image');
    }
docs: JPEG SUPPORT
   takes a string imgData containing the raw bytes of a jpeg image and returns [width, height] Algorithm from: http://www.64lines.com/jpeg-width-height