RainLoop / rainloop-webmail

// (c) 2015 Alasdair Mercer  

// Licensed under the GPL Version 3 license.  

// Based on [jsqrencode](http://code.google.com/p/jsqrencode/)  

// (c) 2010 [email protected]  

// Licensed under the GPL Version 3 license.  

// For all details and documentation:  

// <http://neocotic.com/qr.js>

(function (root) {

  'use strict';

  // Private constants

  // -----------------

  // Alignment pattern.

  var ALIGNMENT_DELTA = [

    0,  11, 15, 19, 23, 27, 31,

    16, 18, 20, 22, 24, 26, 28, 20, 22, 24, 24, 26, 28, 28, 22, 24, 24,

    26, 26, 28, 28, 24, 24, 26, 26, 26, 28, 28, 24, 26, 26, 26, 28, 28

  ];

  // Default MIME type.

  var DEFAULT_MIME = 'image/png';

  // MIME used to initiate a browser download prompt when `qr.save` is called.

  var DOWNLOAD_MIME = 'image/octet-stream';

  // There are four elements per version. The first two indicate the number of blocks, then the

  // data width, and finally the ECC width.

  var ECC_BLOCKS = [

    1,  0,  19,  7,     1,  0,  16,  10,    1,  0,  13,  13,    1,  0,  9,   17,

    1,  0,  34,  10,    1,  0,  28,  16,    1,  0,  22,  22,    1,  0,  16,  28,

    1,  0,  55,  15,    1,  0,  44,  26,    2,  0,  17,  18,    2,  0,  13,  22,

    1,  0,  80,  20,    2,  0,  32,  18,    2,  0,  24,  26,    4,  0,  9,   16,

    1,  0,  108, 26,    2,  0,  43,  24,    2,  2,  15,  18,    2,  2,  11,  22,

    2,  0,  68,  18,    4,  0,  27,  16,    4,  0,  19,  24,    4,  0,  15,  28,

    2,  0,  78,  20,    4,  0,  31,  18,    2,  4,  14,  18,    4,  1,  13,  26,

    2,  0,  97,  24,    2,  2,  38,  22,    4,  2,  18,  22,    4,  2,  14,  26,

    2,  0,  116, 30,    3,  2,  36,  22,    4,  4,  16,  20,    4,  4,  12,  24,

    2,  2,  68,  18,    4,  1,  43,  26,    6,  2,  19,  24,    6,  2,  15,  28,

    4,  0,  81,  20,    1,  4,  50,  30,    4,  4,  22,  28,    3,  8,  12,  24,

    2,  2,  92,  24,    6,  2,  36,  22,    4,  6,  20,  26,    7,  4,  14,  28,

    4,  0,  107, 26,    8,  1,  37,  22,    8,  4,  20,  24,    12, 4,  11,  22,

    3,  1,  115, 30,    4,  5,  40,  24,    11, 5,  16,  20,    11, 5,  12,  24,

    5,  1,  87,  22,    5,  5,  41,  24,    5,  7,  24,  30,    11, 7,  12,  24,

    5,  1,  98,  24,    7,  3,  45,  28,    15, 2,  19,  24,    3,  13, 15,  30,

    1,  5,  107, 28,    10, 1,  46,  28,    1,  15, 22,  28,    2,  17, 14,  28,

    5,  1,  120, 30,    9,  4,  43,  26,    17, 1,  22,  28,    2,  19, 14,  28,

    3,  4,  113, 28,    3,  11, 44,  26,    17, 4,  21,  26,    9,  16, 13,  26,

    3,  5,  107, 28,    3,  13, 41,  26,    15, 5,  24,  30,    15, 10, 15,  28,

    4,  4,  116, 28,    17, 0,  42,  26,    17, 6,  22,  28,    19, 6,  16,  30,

    2,  7,  111, 28,    17, 0,  46,  28,    7,  16, 24,  30,    34, 0,  13,  24,

    4,  5,  121, 30,    4,  14, 47,  28,    11, 14, 24,  30,    16, 14, 15,  30,

    6,  4,  117, 30,    6,  14, 45,  28,    11, 16, 24,  30,    30, 2,  16,  30,

    8,  4,  106, 26,    8,  13, 47,  28,    7,  22, 24,  30,    22, 13, 15,  30,

    10, 2,  114, 28,    19, 4,  46,  28,    28, 6,  22,  28,    33, 4,  16,  30,

    8,  4,  122, 30,    22, 3,  45,  28,    8,  26, 23,  30,    12, 28, 15,  30,

    3,  10, 117, 30,    3,  23, 45,  28,    4,  31, 24,  30,    11, 31, 15,  30,

    7,  7,  116, 30,    21, 7,  45,  28,    1,  37, 23,  30,    19, 26, 15,  30,

    5,  10, 115, 30,    19, 10, 47,  28,    15, 25, 24,  30,    23, 25, 15,  30,

    13, 3,  115, 30,    2,  29, 46,  28,    42, 1,  24,  30,    23, 28, 15,  30,

    17, 0,  115, 30,    10, 23, 46,  28,    10, 35, 24,  30,    19, 35, 15,  30,

    17, 1,  115, 30,    14, 21, 46,  28,    29, 19, 24,  30,    11, 46, 15,  30,

    13, 6,  115, 30,    14, 23, 46,  28,    44, 7,  24,  30,    59, 1,  16,  30,

    12, 7,  121, 30,    12, 26, 47,  28,    39, 14, 24,  30,    22, 41, 15,  30,

    6,  14, 121, 30,    6,  34, 47,  28,    46, 10, 24,  30,    2,  64, 15,  30,

    17, 4,  122, 30,    29, 14, 46,  28,    49, 10, 24,  30,    24, 46, 15,  30,

    4,  18, 122, 30,    13, 32, 46,  28,    48, 14, 24,  30,    42, 32, 15,  30,

    20, 4,  117, 30,    40, 7,  47,  28,    43, 22, 24,  30,    10, 67, 15,  30,

    19, 6,  118, 30,    18, 31, 47,  28,    34, 34, 24,  30,    20, 61, 15,  30

  ];

  // Map of human-readable ECC levels.

  var ECC_LEVELS = {

    L: 1,

    M: 2,

    Q: 3,

    H: 4

  };

  // Final format bits with mask (level << 3 | mask).

  var FINAL_FORMAT = [

    0x77c4, 0x72f3, 0x7daa, 0x789d, 0x662f, 0x6318, 0x6c41, 0x6976, /* L */

    0x5412, 0x5125, 0x5e7c, 0x5b4b, 0x45f9, 0x40ce, 0x4f97, 0x4aa0, /* M */

    0x355f, 0x3068, 0x3f31, 0x3a06, 0x24b4, 0x2183, 0x2eda, 0x2bed, /* Q */

    0x1689, 0x13be, 0x1ce7, 0x19d0, 0x0762, 0x0255, 0x0d0c, 0x083b  /* H */

  ];

  // Galois field exponent table.

  var GALOIS_EXPONENT = [

    0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,

    0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9, 0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,

    0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35, 0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,

    0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0, 0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,

    0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc, 0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,

    0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f, 0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,

    0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88, 0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,

    0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93, 0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,

    0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9, 0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,

    0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa, 0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,

    0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e, 0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,

    0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4, 0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,

    0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e, 0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,

    0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef, 0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,

    0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5, 0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,

    0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83, 0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x00

  ];

  // Galois field log table.

  var GALOIS_LOG = [

    0xff, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6, 0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,

    0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81, 0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,

    0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21, 0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,

    0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9, 0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,

    0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd, 0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,

    0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd, 0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,

    0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e, 0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,

    0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b, 0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,

    0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d, 0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,

    0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c, 0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,

    0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd, 0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,

    0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e, 0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,

    0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76, 0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,

    0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa, 0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,

    0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51, 0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,

    0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8, 0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf

  ];

  // *Badness* coefficients.

  var N1 = 3;

  var N2 = 3;

  var N3 = 40;

  var N4 = 10;

  // Version pattern.

  var VERSION_BLOCK = [ 

    0xc94, 0x5bc, 0xa99, 0x4d3, 0xbf6, 0x762, 0x847, 0x60d, 0x928, 0xb78, 0x45d, 0xa17, 0x532,

    0x9a6, 0x683, 0x8c9, 0x7ec, 0xec4, 0x1e1, 0xfab, 0x08e, 0xc1a, 0x33f, 0xd75, 0x250, 0x9d5,

    0x6f0, 0x8ba, 0x79f, 0xb0b, 0x42e, 0xa64, 0x541, 0xc69

  ];

  // Mode for node.js file system file writes.

  var WRITE_MODE = parseInt('0666', 8);

  // Private variables

  // -----------------

  // Run lengths for badness.

  var badBuffer = [];

  // Constructor for `canvas` elements in the node.js environment.

  var Canvas;

  // Data block.

  var dataBlock;

  // ECC data blocks and tables.

  var eccBlock, neccBlock1, neccBlock2;

  // ECC buffer.

  var eccBuffer = [];

  // ECC level (defaults to **L**).

  var eccLevel = 1;

  // Image buffer.

  var frameBuffer = [];

  // Fixed part of the image.

  var frameMask = [];

  // File system within the node.js environment.

  var fs;

  // Constructor for `img` elements in the node.js environment.

  var Image;

  // Indicates whether or not this script is running in node.js.

  var inNode = false;

  // Generator polynomial.

  var polynomial = [];

  // Save the previous value of the `qr` variable.

  var previousQr = root.qr;

  // Data input buffer.

  var stringBuffer = [];

  // Version for the data.

  var version;

  // Data width is based on `version`.

  var width;

  // Private functions

  // -----------------

  // Create a new canvas  using `document.createElement` unless script is running in node.js, in

  // which case the `canvas` module is used.

  function createCanvas() {

    return inNode ? new Canvas() : root.document.createElement('canvas');

  }

  // Create a new image using `document.createElement` unless script is running in node.js, in

  // which case the `canvas` module is used.

  function createImage() {

    return inNode ? new Image() : root.document.createElement('img');

  }

  // Force the canvas image to be downloaded in the browser.  

  // Optionally, a `callback` function can be specified which will be called upon completed. Since

  // this is not an asynchronous operation, this is merely convenient and helps simplify the

  // calling code.

  function download(cvs, data, callback) {

    var mime = data.mime || DEFAULT_MIME;

    root.location.href = cvs.toDataURL(mime).replace(mime, DOWNLOAD_MIME);

    if (typeof callback === 'function') callback();

  }

  // Normalize the `data` that is provided to the main API.

  function normalizeData(data) {

    if (typeof data === 'string') data = { value: data };

    return data || {};

  }

  // Override the `qr` API methods that require HTML5 canvas support to throw a relevant error.

  function overrideAPI(qr) {

    var methods = [ 'canvas', 'image', 'save', 'saveSync', 'toDataURL' ];

    var i;

    function overrideMethod(name) {

      qr[name] = function () {

        throw new Error(name + ' requires HTML5 canvas element support');

      };

    }

    for (i = 0; i < methods.length; i++) {

      overrideMethod(methods[i]);

    }

  }

  // Asynchronously write the data of the rendered canvas to a given file path.

  function writeFile(cvs, data, callback) {

    if (typeof data.path !== 'string') {

      return callback(new TypeError('Invalid path type: ' + typeof data.path));

    }

    var fd, buff;

    // Write the buffer to the open file stream once both prerequisites are met.

    function writeBuffer() {

      fs.write(fd, buff, 0, buff.length, 0, function (error) {

        fs.close(fd);

        callback(error);

      });

    }

    // Create a buffer of the canvas' data.

    cvs.toBuffer(function (error, _buff) {

      if (error) return callback(error);

      buff = _buff;

      if (fd) {

        writeBuffer();

      }

    });

    // Open a stream for the file to be written.

    fs.open(data.path, 'w', WRITE_MODE, function (error, _fd) {

      if (error) return callback(error);

      fd = _fd;

      if (buff) {

        writeBuffer();

      }

    });

  }

  // Write the data of the rendered canvas to a given file path.

  function writeFileSync(cvs, data) {

    if (typeof data.path !== 'string') {

      throw new TypeError('Invalid path type: ' + typeof data.path);

    }

    var buff = cvs.toBuffer();

    var fd = fs.openSync(data.path, 'w', WRITE_MODE);

    try {

      fs.writeSync(fd, buff, 0, buff.length, 0);

    } finally {

      fs.closeSync(fd);

    }

  }

  // Set bit to indicate cell in frame is immutable (symmetric around diagonal).

  function setMask(x, y) {

    var bit;

    if (x > y) {

      bit = x;

      x   = y;

      y   = bit;

    }

    bit   = y;

    bit  *= y;

    bit  += y;

    bit >>= 1;

    bit  += x;

    frameMask[bit] = 1;

  }

  // Enter alignment pattern. Foreground colour to frame, background to mask. Frame will be merged

  // with mask later.

  function addAlignment(x, y) {

    var i;

    frameBuffer[x + width * y] = 1;

    for (i = -2; i < 2; i++) {

      frameBuffer[(x + i)     + width * (y - 2)]     = 1;

      frameBuffer[(x - 2)     + width * (y + i + 1)] = 1;

      frameBuffer[(x + 2)     + width * (y + i)]     = 1;

      frameBuffer[(x + i + 1) + width * (y + 2)]     = 1;

    }

    for (i = 0; i < 2; i++) {

      setMask(x - 1, y + i);

      setMask(x + 1, y - i);

      setMask(x - i, y - 1);

      setMask(x + i, y + 1);

    }

  }

  // Exponentiation mod N.

  function modN(x) {

    while (x >= 255) {

      x -= 255;

      x  = (x >> 8) + (x & 255);

    }

    return x;

  }

  // Calculate and append `ecc` data to the `data` block. If block is in the string buffer the

  // indices to buffers are used.

  function appendData(data, dataLength, ecc, eccLength) {

    var bit, i, j;

    for (i = 0; i < eccLength; i++) {

      stringBuffer[ecc + i] = 0;

    }

    for (i = 0; i < dataLength; i++) {

      bit = GALOIS_LOG[stringBuffer[data + i] ^ stringBuffer[ecc]];

      if (bit !== 255) {

        for (j = 1; j < eccLength; j++) {

          stringBuffer[ecc + j - 1] = stringBuffer[ecc + j] ^

              GALOIS_EXPONENT[modN(bit + polynomial[eccLength - j])];

        }

      } else {

        for (j = ecc; j < ecc + eccLength; j++) {

          stringBuffer[j] = stringBuffer[j + 1];

        }

      }

      stringBuffer[ecc + eccLength - 1] = bit === 255 ? 0 :

          GALOIS_EXPONENT[modN(bit + polynomial[0])];

    }

  }

  // Check mask since symmetricals use half.

  function isMasked(x, y) {

    var bit;

    if (x > y) {

      bit = x;

      x   = y;

      y   = bit;

    }

    bit   = y;

    bit  += y * y;

    bit >>= 1;

    bit  += x;

    return frameMask[bit] === 1;

  }

  // Apply the selected mask out of the 8 options.

  function applyMask(mask) {

    var x, y, r3x, r3y;

    switch (mask) {

      case 0:

        for (y = 0; y < width; y++) {

          for (x = 0; x < width; x++) {

            if (!((x + y) & 1) && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

      case 1:

        for (y = 0; y < width; y++) {

          for (x = 0; x < width; x++) {

            if (!(y & 1) && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

      case 2:

        for (y = 0; y < width; y++) {

          for (r3x = 0, x = 0; x < width; x++, r3x++) {

            if (r3x === 3) r3x = 0;

            if (!r3x && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

      case 3:

        for (r3y = 0, y = 0; y < width; y++, r3y++) {

          if (r3y === 3) r3y = 0;

          for (r3x = r3y, x = 0; x < width; x++, r3x++) {

            if (r3x === 3) r3x = 0;

            if (!r3x && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

      case 4:

        for (y = 0; y < width; y++) {

          for (r3x = 0, r3y = ((y >> 1) & 1), x = 0; x < width; x++, r3x++) {

            if (r3x === 3) {

              r3x = 0;

              r3y = !r3y;

            }

            if (!r3y && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

      case 5:

        for (r3y = 0, y = 0; y < width; y++, r3y++) {

          if (r3y === 3) r3y = 0;

          for (r3x = 0, x = 0; x < width; x++, r3x++) {

            if (r3x === 3) r3x = 0;

            if (!((x & y & 1) + !(!r3x | !r3y)) && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

      case 6:

        for (r3y = 0, y = 0; y < width; y++, r3y++) {

          if (r3y === 3) r3y = 0;

          for (r3x = 0, x = 0; x < width; x++, r3x++) {

            if (r3x === 3) r3x = 0;

            if (!(((x & y & 1) + (r3x && (r3x === r3y))) & 1) && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

      case 7:

        for (r3y = 0, y = 0; y < width; y++, r3y++) {

          if (r3y === 3) r3y = 0;

          for (r3x = 0, x = 0; x < width; x++, r3x++) {

            if (r3x === 3) r3x = 0;

            if (!(((r3x && (r3x === r3y)) + ((x + y) & 1)) & 1) && !isMasked(x, y)) {

              frameBuffer[x + y * width] ^= 1;

            }

          }

        }

        break;

    }

  }

  // Using the table for the length of each run, calculate the amount of bad image. Long runs or

  // those that look like finders are called twice; once for X and Y.

  function getBadRuns(length) {

    var badRuns = 0;

    var i;

    for (i = 0; i <= length; i++) {

      if (badBuffer[i] >= 5) {

        badRuns += N1 + badBuffer[i] - 5;

      }

    }

    // FBFFFBF as in finder.

    for (i = 3; i < length - 1; i += 2) {

      if (badBuffer[i - 2] === badBuffer[i + 2] &&

          badBuffer[i + 2] === badBuffer[i - 1] &&

          badBuffer[i - 1] === badBuffer[i + 1] &&

          badBuffer[i - 1] * 3 === badBuffer[i] &&

          // Background around the foreground pattern? Not part of the specs.

          (badBuffer[i - 3] === 0 || i + 3 > length ||

           badBuffer[i - 3] * 3 >= badBuffer[i] * 4 ||

           badBuffer[i + 3] * 3 >= badBuffer[i] * 4)) {

        badRuns += N3;

      }

    }

    return badRuns;

  }

  // Calculate how bad the masked image is (e.g. blocks, imbalance, runs, or finders).

  function checkBadness() {

    var b, b1, bad, big, bw, count, h, x, y;

    bad = bw = count = 0;

    // Blocks of same colour.

    for (y = 0; y < width - 1; y++) {

      for (x = 0; x < width - 1; x++) {

            // All foreground colour.

        if ((frameBuffer[x + width * y] &&

             frameBuffer[(x + 1) + width * y] &&

             frameBuffer[x + width * (y + 1)] &&

             frameBuffer[(x + 1) + width * (y + 1)]) ||

            // All background colour.

            !(frameBuffer[x + width * y] ||

              frameBuffer[(x + 1) + width * y] ||

              frameBuffer[x + width * (y + 1)] ||

              frameBuffer[(x + 1) + width * (y + 1)])) {

          bad += N2;

        }

      }

    }

    // X runs.

    for (y = 0; y < width; y++) {

      badBuffer[0] = 0;

      for (h = b = x = 0; x < width; x++) {

        if ((b1 = frameBuffer[x + width * y]) === b) {

          badBuffer[h]++;

        } else {

          badBuffer[++h] = 1;

        }

        b   = b1;

        bw += b ? 1 : -1;

      }

      bad += getBadRuns(h);

    }

    if (bw < 0) bw = -bw;

    big   = bw;

    big  += big << 2;

    big <<= 1;

    while (big > width * width) {

      big -= width * width;

      count++;

    }

    bad += count * N4;

    // Y runs.

    for (x = 0; x < width; x++) {

      badBuffer[0] = 0;

      for (h = b = y = 0; y < width; y++) {

        if ((b1 = frameBuffer[x + width * y]) === b) {

          badBuffer[h]++;

        } else {

          badBuffer[++h] = 1;

        }

        b = b1;

      }

      bad += getBadRuns(h);

    }

    return bad;

  }

  // Generate the encoded QR image for the string provided.

  // qr.js setup

  // -----------

  // Build the publicly exposed API.

  var qr = {

    // Constants

    // ---------

    // Current version of `qr`.

    VERSION: '1.1.4',

    // QR functions

    // ------------

    // Generate the QR code using the data provided and render it on to a `<canvas>` element.  

    // If no `<canvas>` element is specified in the argument provided a new one will be created and

    // used.  

    // ECC (error correction capacity) determines how many intential errors are contained in the QR

    // code.

    canvas: function(data) {

      data = normalizeData(data);

      // Module size of the generated QR code (i.e. 1-10).

      var size = data.size >= 1 && data.size <= 10 ? data.size : 4;

      // Actual size of the QR code symbol and is scaled to 25 pixels (e.g. 1 = 25px, 3 = 75px).

      size *= 25;

      // `<canvas>` element used to render the QR code.

      var cvs = data.canvas || createCanvas();

      // Retreive the 2D context of the canvas.

      var c2d = cvs.getContext('2d');

      // Ensure the canvas has the correct dimensions.

      c2d.canvas.width  = size;

      c2d.canvas.height = size;

      // Fill the canvas with the correct background colour.

      c2d.fillStyle = data.background || '#fff';

      c2d.fillRect(0, 0, size, size);

      // Determine the ECC level to be applied.

      eccLevel = ECC_LEVELS[(data.level && data.level.toUpperCase()) || 'L'];

      // Generate the image frame for the given `value`.

      var frame = generateFrame(data.value || '');

      c2d.lineWidth = 1;

      // Determine the *pixel* size.

      var px = size;

      px /= width;

      px  = Math.floor(px);

      var offset = Math.floor((size - (px * width)) / 2);

      // Draw the QR code.

      c2d.clearRect(0, 0, size, size);

      c2d.fillStyle = data.background || '#fff';

      c2d.fillRect(0, 0, size, size);

      c2d.fillStyle = data.foreground || '#000';

      var i, j;

      for (i = 0; i < width; i++) {

        for (j = 0; j < width; j++) {

          if (frame[j * width + i]) {

            c2d.fillRect(px * i + offset, px * j + offset, px, px);

          }

        }

      }

      return cvs;

    },

    // Generate the QR code using the data provided and render it on to a `<img>` element.  

    // If no `<img>` element is specified in the argument provided a new one will be created and

    // used.  

    // ECC (error correction capacity) determines how many intential errors are contained in the QR

    // code.

    image: function(data) {

      data = normalizeData(data);

      // `<canvas>` element only which the QR code is rendered.

      var cvs = this.canvas(data);

      // `<img>` element used to display the QR code.

      var img = data.image || createImage();

      // Apply the QR code to `img`.

      img.src    = cvs.toDataURL(data.mime || DEFAULT_MIME);

      img.height = cvs.height;

      img.width  = cvs.width;

      return img;

    },

    // Generate the QR code using the data provided and render it on to a `<canvas>` element and

    // save it as an image file.  

    // If no `<canvas>` element is specified in the argument provided a new one will be created and

    // used.  

    // ECC (error correction capacity) determines how many intential errors are contained in the QR

    // code.  

    // If called in a browser the `path` property/argument is ignored and will simply prompt the

    // user to choose a location and file name. However, if called within node.js the file will be

    // saved to specified path.  

    // A `callback` function must be provided which will be called once the saving process has

    // started. If an error occurs it will be passed as the first argument to this function,

    // otherwise this argument will be `null`.

    save: function(data, path, callback) {

      data = normalizeData(data);

      switch (typeof path) {