微信小程序之生成条形码和二维码

需求描述：商家用扫描枪扫用户条形码或二维码实现支付。

效果图：

说明：微信小程序、支付宝小程序的条形码和二维码都可以由一串数字通过 barcode.js 和 qrcode.js 插件绘制在页面的 Canvas 元素上。

两个插件的内容我贴在文章末尾

下面我总结一下基于微信小程序的整个实现流程：

（支付宝小程序类似，只要在微信小程序的基础上稍微改一下就行了）

1. 从后台获取要转换成条形码和二维码的一串数字 code

2. 分别用 barcode.js 和 qrcode.js 把数字绘制成页面canvas里的条形码和二维码

wxml: 

     
     {{codeStr}}
     

utils.js

import qrcode from './qrcode';
import barcode from './barcode';

// 插件内部是根据width, height参数的rpx值来进行绘画
// 把数字转换成条形码
function toBarcode (canvasId, code, width, height) {
    barcode.code128(wx.createCanvasContext(canvasId), code, width, height);
}

// 把数字转换成二维码
function toQrcode (canvasId, code, width, height) {
    qrcode.api.draw(code, {
        ctx: wx.createCanvasContext(canvasId),
        width,
        height
    })
}

export {
    toBarcode,
    toQrcode
}

// 使用 api

const code = '1221334122546765342';

toBarcode('barcode', code, 680, 200);
toQrcode('qrcode', code, 420, 420);
const codeStr = `${code.slice(0, 4)}****${code.slice(20)}`;

3. 轮询请求后台，查看是否已被扫码（其实就是判断后台返回的 code 状态）

        getStatus(code);

        function getStatus (code) {
            wx.request({
                url: '/api/xxx',
                method: 'GET',
                data: {code},
                success: (res) => {
                    if (res.isSuccess) {
                        // 支付成功后的操作
                    } else {
                        // 还未支付并且允许轮训的话就继续轮训
                        if (this.state.caninterval) {
                            setTimeout(() => {
                                getStatus(code);
                            }, 1500)
                        }
                    }
                }
            })
        }

完整代码：

import { toBarcode, toQrcode } from '../utils';

Page({
    data: {
        canInterval: true, //判断能不能轮询，作用是控制小程序切换到后台时不进行轮训
        code: '', // 转换成条形码、二维码的数字
        codeStr: ''
    },

    onLoad () {
        wx.request({
            url: '/api/xxx',
            method: 'GET',
            success: (res) => {
                const { code } = res.data;
                toBarcode('barcode', code , 680, 200);
                toQrcode('qrcode', code, 420, 420);
                const codeStr = `${code.slice(0, 4)}****${code.slice(20)}`;

                this.setData({
                    code,
                    codeStr
                })

                this.getStatus(code);
            }
        })
    },

    onShow () {
        const {code} = this.data;

        this.setData({
            canInterval: true
        });

        code && this.getStatus(code);
    },

    getStatus (code) {
        wx.request({
            url: '',
            method: 'GET',
            data: {code},
            success: (res) => {
                if (res.isSuccess) {
                    // 支付成功后的操作
                } else {
                    // 还未支付并且允许轮训的话就继续轮训
                    if (this.state.canInterval) {
                        setTimeout(() => {
                            this.getStatus(code);
                        }, 1000)
                    }
                }
            }
        })
    },

    onHide () {
        this.setData({
            canInterval: false
        })
    },

    onUnload () {
        this.setData({
            canInterval: false
        })
    }
})

附赠两个插件

barcode.js

/** 
// https://github.com/alsey/wxbarcode
// 最后一位显示 _ 问题
// https://github.com/alsey/wxbarcode/issues/2
// //ok some type of shift is nessecary if (shifter != -1) { result.push(shifter); result.push(codeValue(chr1));//把这里的chr2改成chr1即可。 }
**/

!(function(){
var CHAR_TILDE = 126;
var CODE_FNC1 = 102;

var SET_STARTA = 103;
var SET_STARTB = 104;
var SET_STARTC = 105;
var SET_SHIFT = 98;
var SET_CODEA = 101;
var SET_CODEB = 100;
var SET_STOP = 106;


var REPLACE_CODES = {
    CHAR_TILDE: CODE_FNC1 //~ corresponds to FNC1 in GS1-128 standard
}

var CODESET = {
    ANY: 1,
    AB: 2,
    A: 3,
    B: 4,
    C: 5
};

function getBytes(str) {
    var bytes = [];
    for (var i = 0; i < str.length; i++) {
        bytes.push(str.charCodeAt(i));
    }
    return bytes;
}

exports.code128 = function (ctx, text, width, height) {

    width = parseInt(width);

    height = parseInt(height);

    var codes = stringToCode128(text);

    var g = new Graphics(ctx, width, height);

    var barWeight = g.area.width / ((codes.length - 3) * 11 + 35);

    var x = g.area.left;
    var y = g.area.top;
    for (var i = 0; i < codes.length; i++) {
        var c = codes[i];
        //two bars at a time: 1 black and 1 white
        for (var bar = 0; bar < 8; bar += 2) {
            var barW = PATTERNS[c][bar] * barWeight;
            // var barH = height - y - this.border;
            var barH = height - y;
            var spcW = PATTERNS[c][bar + 1] * barWeight;

            //no need to draw if 0 width
            if (barW > 0) {
                g.fillFgRect(x, y, barW, barH);
            }

            x += barW + spcW;
        }
    }

    ctx.draw();
}


function stringToCode128(text) {

    var barc = {
        currcs: CODESET.C
    };

    var bytes = getBytes(text);
    //decide starting codeset
    var index = bytes[0] == CHAR_TILDE ? 1 : 0;

    var csa1 = bytes.length > 0 ? codeSetAllowedFor(bytes[index++]) : CODESET.AB;
    var csa2 = bytes.length > 0 ? codeSetAllowedFor(bytes[index++]) : CODESET.AB;
    barc.currcs = getBestStartSet(csa1, csa2);
    barc.currcs = perhapsCodeC(bytes, barc.currcs);

    //if no codeset changes this will end up with bytes.length+3
    //start, checksum and stop
    var codes = new Array();

    switch (barc.currcs) {
        case CODESET.A:
            codes.push(SET_STARTA);
            break;
        case CODESET.B:
            codes.push(SET_STARTB);
            break;
        default:
            codes.push(SET_STARTC);
            break;
    }


    for (var i = 0; i < bytes.length; i++) {
        var b1 = bytes[i]; //get the first of a pair
        //should we translate/replace
        if (b1 in REPLACE_CODES) {
            codes.push(REPLACE_CODES[b1]);
            i++ //jump to next
            b1 = bytes[i];
        }

        //get the next in the pair if possible
        var b2 = bytes.length > (i + 1) ? bytes[i + 1] : -1;

        codes = codes.concat(codesForChar(b1, b2, barc.currcs));
        //code C takes 2 chars each time
        if (barc.currcs == CODESET.C) i++;
    }

    //calculate checksum according to Code 128 standards
    var checksum = codes[0];
    for (var weight = 1; weight < codes.length; weight++) {
        checksum += (weight * codes[weight]);
    }
    codes.push(checksum % 103);

    codes.push(SET_STOP);

    //encoding should now be complete
    return codes;

    function getBestStartSet(csa1, csa2) {
        //tries to figure out the best codeset
        //to start with to get the most compact code
        var vote = 0;
        vote += csa1 == CODESET.A ? 1 : 0;
        vote += csa1 == CODESET.B ? -1 : 0;
        vote += csa2 == CODESET.A ? 1 : 0;
        vote += csa2 == CODESET.B ? -1 : 0;
        //tie goes to B due to my own predudices
        return vote > 0 ? CODESET.A : CODESET.B;
    }

    function perhapsCodeC(bytes, codeset) {
        for (var i = 0; i < bytes.length; i++) {
            var b = bytes[i]
            if ((b < 48 || b > 57) && b != CHAR_TILDE)
                return codeset;
        }
        return CODESET.C;
    }

    //chr1 is current byte
    //chr2 is the next byte to process. looks ahead.
    function codesForChar(chr1, chr2, currcs) {
        var result = [];
        var shifter = -1;

        if (charCompatible(chr1, currcs)) {
            if (currcs == CODESET.C) {
                if (chr2 == -1) {
                    shifter = SET_CODEB;
                    currcs = CODESET.B;
                }
                else if ((chr2 != -1) && !charCompatible(chr2, currcs)) {
                    //need to check ahead as well
                    if (charCompatible(chr2, CODESET.A)) {
                        shifter = SET_CODEA;
                        currcs = CODESET.A;
                    }
                    else {
                        shifter = SET_CODEB;
                        currcs = CODESET.B;
                    }
                }
            }
        }
        else {
            //if there is a next char AND that next char is also not compatible
            if ((chr2 != -1) && !charCompatible(chr2, currcs)) {
                //need to switch code sets
                switch (currcs) {
                    case CODESET.A:
                        shifter = SET_CODEB;
                        currcs = CODESET.B;
                        break;
                    case CODESET.B:
                        shifter = SET_CODEA;
                        currcs = CODESET.A;
                        break;
                }
            }
            else {
                //no need to shift code sets, a temporary SHIFT will suffice
                shifter = SET_SHIFT;
            }
        }

        //ok some type of shift is nessecary
        if (shifter != -1) {
            result.push(shifter);
            result.push(codeValue(chr1));
        }
        else {
            if (currcs == CODESET.C) {
                //include next as well
                result.push(codeValue(chr1, chr2));
            }
            else {
                result.push(codeValue(chr1));
            }
        }
        barc.currcs = currcs;

        return result;
    }
}

//reduce the ascii code to fit into the Code128 char table
function codeValue(chr1, chr2) {
    if (typeof chr2 == "undefined") {
        return chr1 >= 32 ? chr1 - 32 : chr1 + 64;
    }
    else {
        return parseInt(String.fromCharCode(chr1) + String.fromCharCode(chr2));
    }
}

function charCompatible(chr, codeset) {
    var csa = codeSetAllowedFor(chr);
    if (csa == CODESET.ANY) return true;
    //if we need to change from current
    if (csa == CODESET.AB) return true;
    if (csa == CODESET.A && codeset == CODESET.A) return true;
    if (csa == CODESET.B && codeset == CODESET.B) return true;
    return false;
}

function codeSetAllowedFor(chr) {
    if (chr >= 48 && chr <= 57) {
        //0-9
        return CODESET.ANY;
    }
    else if (chr >= 32 && chr <= 95) {
        //0-9 A-Z
        return CODESET.AB;
    }
    else {
        //if non printable
        return chr < 32 ? CODESET.A : CODESET.B;
    }
}

var Graphics = function(ctx, width, height) {

    this.width = width;
    this.height = height;
    this.quiet = Math.round(this.width / 40);

    this.border_size   = 0;
    this.padding_width = 0;

    this.area = {
        width : width - this.padding_width * 2 - this.quiet * 2,
        height: height - this.border_size * 2,
        top   : this.border_size - 4,
        left  : this.padding_width + this.quiet
    };

    this.ctx = ctx;
    this.fg = "#000000";
    this.bg = "#ffffff";

    // fill background
    this.fillBgRect(0,0, width, height);

    // fill center to create border
    this.fillBgRect(0, this.border_size, width, height - this.border_size * 2);
}

//use native color
Graphics.prototype._fillRect = function(x, y, width, height, color) {
    this.ctx.setFillStyle(color)
    this.ctx.fillRect(x, y, width, height)
}

Graphics.prototype.fillFgRect = function(x,y, width, height) {
    this._fillRect(x, y, width, height, this.fg);
}

Graphics.prototype.fillBgRect = function(x,y, width, height) {
    this._fillRect(x, y, width, height, this.bg);
}

var PATTERNS = [
    [2, 1, 2, 2, 2, 2, 0, 0],  // 0
    [2, 2, 2, 1, 2, 2, 0, 0],  // 1
    [2, 2, 2, 2, 2, 1, 0, 0],  // 2
    [1, 2, 1, 2, 2, 3, 0, 0],  // 3
    [1, 2, 1, 3, 2, 2, 0, 0],  // 4
    [1, 3, 1, 2, 2, 2, 0, 0],  // 5
    [1, 2, 2, 2, 1, 3, 0, 0],  // 6
    [1, 2, 2, 3, 1, 2, 0, 0],  // 7
    [1, 3, 2, 2, 1, 2, 0, 0],  // 8
    [2, 2, 1, 2, 1, 3, 0, 0],  // 9
    [2, 2, 1, 3, 1, 2, 0, 0],  // 10
    [2, 3, 1, 2, 1, 2, 0, 0],  // 11
    [1, 1, 2, 2, 3, 2, 0, 0],  // 12
    [1, 2, 2, 1, 3, 2, 0, 0],  // 13
    [1, 2, 2, 2, 3, 1, 0, 0],  // 14
    [1, 1, 3, 2, 2, 2, 0, 0],  // 15
    [1, 2, 3, 1, 2, 2, 0, 0],  // 16
    [1, 2, 3, 2, 2, 1, 0, 0],  // 17
    [2, 2, 3, 2, 1, 1, 0, 0],  // 18
    [2, 2, 1, 1, 3, 2, 0, 0],  // 19
    [2, 2, 1, 2, 3, 1, 0, 0],  // 20
    [2, 1, 3, 2, 1, 2, 0, 0],  // 21
    [2, 2, 3, 1, 1, 2, 0, 0],  // 22
    [3, 1, 2, 1, 3, 1, 0, 0],  // 23
    [3, 1, 1, 2, 2, 2, 0, 0],  // 24
    [3, 2, 1, 1, 2, 2, 0, 0],  // 25
    [3, 2, 1, 2, 2, 1, 0, 0],  // 26
    [3, 1, 2, 2, 1, 2, 0, 0],  // 27
    [3, 2, 2, 1, 1, 2, 0, 0],  // 28
    [3, 2, 2, 2, 1, 1, 0, 0],  // 29
    [2, 1, 2, 1, 2, 3, 0, 0],  // 30
    [2, 1, 2, 3, 2, 1, 0, 0],  // 31
    [2, 3, 2, 1, 2, 1, 0, 0],  // 32
    [1, 1, 1, 3, 2, 3, 0, 0],  // 33
    [1, 3, 1, 1, 2, 3, 0, 0],  // 34
    [1, 3, 1, 3, 2, 1, 0, 0],  // 35
    [1, 1, 2, 3, 1, 3, 0, 0],  // 36
    [1, 3, 2, 1, 1, 3, 0, 0],  // 37
    [1, 3, 2, 3, 1, 1, 0, 0],  // 38
    [2, 1, 1, 3, 1, 3, 0, 0],  // 39
    [2, 3, 1, 1, 1, 3, 0, 0],  // 40
    [2, 3, 1, 3, 1, 1, 0, 0],  // 41
    [1, 1, 2, 1, 3, 3, 0, 0],  // 42
    [1, 1, 2, 3, 3, 1, 0, 0],  // 43
    [1, 3, 2, 1, 3, 1, 0, 0],  // 44
    [1, 1, 3, 1, 2, 3, 0, 0],  // 45
    [1, 1, 3, 3, 2, 1, 0, 0],  // 46
    [1, 3, 3, 1, 2, 1, 0, 0],  // 47
    [3, 1, 3, 1, 2, 1, 0, 0],  // 48
    [2, 1, 1, 3, 3, 1, 0, 0],  // 49
    [2, 3, 1, 1, 3, 1, 0, 0],  // 50
    [2, 1, 3, 1, 1, 3, 0, 0],  // 51
    [2, 1, 3, 3, 1, 1, 0, 0],  // 52
    [2, 1, 3, 1, 3, 1, 0, 0],  // 53
    [3, 1, 1, 1, 2, 3, 0, 0],  // 54
    [3, 1, 1, 3, 2, 1, 0, 0],  // 55
    [3, 3, 1, 1, 2, 1, 0, 0],  // 56
    [3, 1, 2, 1, 1, 3, 0, 0],  // 57
    [3, 1, 2, 3, 1, 1, 0, 0],  // 58
    [3, 3, 2, 1, 1, 1, 0, 0],  // 59
    [3, 1, 4, 1, 1, 1, 0, 0],  // 60
    [2, 2, 1, 4, 1, 1, 0, 0],  // 61
    [4, 3, 1, 1, 1, 1, 0, 0],  // 62
    [1, 1, 1, 2, 2, 4, 0, 0],  // 63
    [1, 1, 1, 4, 2, 2, 0, 0],  // 64
    [1, 2, 1, 1, 2, 4, 0, 0],  // 65
    [1, 2, 1, 4, 2, 1, 0, 0],  // 66
    [1, 4, 1, 1, 2, 2, 0, 0],  // 67
    [1, 4, 1, 2, 2, 1, 0, 0],  // 68
    [1, 1, 2, 2, 1, 4, 0, 0],  // 69
    [1, 1, 2, 4, 1, 2, 0, 0],  // 70
    [1, 2, 2, 1, 1, 4, 0, 0],  // 71
    [1, 2, 2, 4, 1, 1, 0, 0],  // 72
    [1, 4, 2, 1, 1, 2, 0, 0],  // 73
    [1, 4, 2, 2, 1, 1, 0, 0],  // 74
    [2, 4, 1, 2, 1, 1, 0, 0],  // 75
    [2, 2, 1, 1, 1, 4, 0, 0],  // 76
    [4, 1, 3, 1, 1, 1, 0, 0],  // 77
    [2, 4, 1, 1, 1, 2, 0, 0],  // 78
    [1, 3, 4, 1, 1, 1, 0, 0],  // 79
    [1, 1, 1, 2, 4, 2, 0, 0],  // 80
    [1, 2, 1, 1, 4, 2, 0, 0],  // 81
    [1, 2, 1, 2, 4, 1, 0, 0],  // 82
    [1, 1, 4, 2, 1, 2, 0, 0],  // 83
    [1, 2, 4, 1, 1, 2, 0, 0],  // 84
    [1, 2, 4, 2, 1, 1, 0, 0],  // 85
    [4, 1, 1, 2, 1, 2, 0, 0],  // 86
    [4, 2, 1, 1, 1, 2, 0, 0],  // 87
    [4, 2, 1, 2, 1, 1, 0, 0],  // 88
    [2, 1, 2, 1, 4, 1, 0, 0],  // 89
    [2, 1, 4, 1, 2, 1, 0, 0],  // 90
    [4, 1, 2, 1, 2, 1, 0, 0],  // 91
    [1, 1, 1, 1, 4, 3, 0, 0],  // 92
    [1, 1, 1, 3, 4, 1, 0, 0],  // 93
    [1, 3, 1, 1, 4, 1, 0, 0],  // 94
    [1, 1, 4, 1, 1, 3, 0, 0],  // 95
    [1, 1, 4, 3, 1, 1, 0, 0],  // 96
    [4, 1, 1, 1, 1, 3, 0, 0],  // 97
    [4, 1, 1, 3, 1, 1, 0, 0],  // 98
    [1, 1, 3, 1, 4, 1, 0, 0],  // 99
    [1, 1, 4, 1, 3, 1, 0, 0],  // 100
    [3, 1, 1, 1, 4, 1, 0, 0],  // 101
    [4, 1, 1, 1, 3, 1, 0, 0],  // 102
    [2, 1, 1, 4, 1, 2, 0, 0],  // 103
    [2, 1, 1, 2, 1, 4, 0, 0],  // 104
    [2, 1, 1, 2, 3, 2, 0, 0],  // 105
    [2, 3, 3, 1, 1, 1, 2, 0]   // 106
]
})();

qrcode.js

var QR = (function () {

    // alignment pattern
    var adelta = [
      0, 11, 15, 19, 23, 27, 31, // force 1 pat
      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
      ];

    // version block
    var vpat = [
        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
    ];

    // final format bits with mask: level << 3 | mask
    var fmtword = [
        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
    ];

    // 4 per version: number of blocks 1,2; data width; ecc width
    var eccblocks = [
        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
    ];

    // Galois field log table
    var glog = [
        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
    ];

    // Galios field exponent table
    var gexp = [
        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
    ];

    // Working buffers:
    // data input and ecc append, image working buffer, fixed part of image, run lengths for badness
    var strinbuf=[], eccbuf=[], qrframe=[], framask=[], rlens=[]; 
    // Control values - width is based on version, last 4 are from table.
    var version, width, neccblk1, neccblk2, datablkw, eccblkwid;
    var ecclevel = 2;
    // set bit to indicate cell in qrframe is immutable.  symmetric around diagonal
    function setmask(x, y)
    {
        var bt;
        if (x > y) {
            bt = x;
            x = y;
            y = bt;
        }
        // y*y = 1+3+5...
        bt = y;
        bt *= y;
        bt += y;
        bt >>= 1;
        bt += x;
        framask[bt] = 1;
    }

    // enter alignment pattern - black to qrframe, white to mask (later black frame merged to mask)
    function putalign(x, y)
    {
        var j;

        qrframe[x + width * y] = 1;
        for (j = -2; j < 2; j++) {
            qrframe[(x + j) + width * (y - 2)] = 1;
            qrframe[(x - 2) + width * (y + j + 1)] = 1;
            qrframe[(x + 2) + width * (y + j)] = 1;
            qrframe[(x + j + 1) + width * (y + 2)] = 1;
        }
        for (j = 0; j < 2; j++) {
            setmask(x - 1, y + j);
            setmask(x + 1, y - j);
            setmask(x - j, y - 1);
            setmask(x + j, y + 1);
        }
    }

    //========================================================================
    // Reed Solomon error correction
    // exponentiation mod N
    function modnn(x)
    {
        while (x >= 255) {
            x -= 255;
            x = (x >> 8) + (x & 255);
        }
        return x;
    }

    var genpoly = [];

    // Calculate and append ECC data to data block.  Block is in strinbuf, indexes to buffers given.
    function appendrs(data, dlen, ecbuf, eclen)
    {
        var i, j, fb;

        for (i = 0; i < eclen; i++)
            strinbuf[ecbuf + i] = 0;
        for (i = 0; i < dlen; i++) {
            fb = glog[strinbuf[data + i] ^ strinbuf[ecbuf]];
            if (fb != 255)     /* fb term is non-zero */
                for (j = 1; j < eclen; j++)
                    strinbuf[ecbuf + j - 1] = strinbuf[ecbuf + j] ^ gexp[modnn(fb + genpoly[eclen - j])];
            else
                for( j = ecbuf ; j < ecbuf + eclen; j++ )
                    strinbuf[j] = strinbuf[j + 1];
            strinbuf[ ecbuf + eclen - 1] = fb == 255 ? 0 : gexp[modnn(fb + genpoly[0])];
        }
    }

    //========================================================================
    // Frame data insert following the path rules

    // check mask - since symmetrical use half.
    function ismasked(x, y)
    {
        var bt;
        if (x > y) {
            bt = x;
            x = y;
            y = bt;
        }
        bt = y;
        bt += y * y;
        bt >>= 1;
        bt += x;
        return framask[bt];
    }

    //========================================================================
    //  Apply the selected mask out of the 8.
    function  applymask(m)
    {
        var x, y, r3x, r3y;

        switch (m) {
        case 0:
            for (y = 0; y < width; y++)
                for (x = 0; x < width; x++)
                    if (!((x + y) & 1) && !ismasked(x, y))
                        qrframe[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))
                        qrframe[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))
                        qrframe[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))
                        qrframe[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))
                        qrframe[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))
                        qrframe[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))
                        qrframe[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))
                        qrframe[x + y * width] ^= 1;
                }
            }
            break;
        }
        return;
    }

    // Badness coefficients.
    var N1 = 3, N2 = 3, N3 = 40, N4 = 10;

    // Using the table of the length of each run, calculate the amount of bad image 
    // - long runs or those that look like finders; called twice, once each for X and Y
    function badruns(length)
    {
        var i;
        var runsbad = 0;
        for (i = 0; i <= length; i++)
            if (rlens[i] >= 5)
                runsbad += N1 + rlens[i] - 5;
        // BwBBBwB as in finder
        for (i = 3; i < length - 1; i += 2)
            if (rlens[i - 2] == rlens[i + 2]
                && rlens[i + 2] == rlens[i - 1]
                && rlens[i - 1] == rlens[i + 1]
                && rlens[i - 1] * 3 == rlens[i]
                // white around the black pattern? Not part of spec
                && (rlens[i - 3] == 0 // beginning
                    || i + 3 > length  // end
                    || rlens[i - 3] * 3 >= rlens[i] * 4 || rlens[i + 3] * 3 >= rlens[i] * 4)
               )
                runsbad += N3;
        return runsbad;
    }

    // Calculate how bad the masked image is - blocks, imbalance, runs, or finders.
    function badcheck()
    {
        var x, y, h, b, b1;
        var thisbad = 0;
        var bw = 0;

        // blocks of same color.
        for (y = 0; y < width - 1; y++)
            for (x = 0; x < width - 1; x++)
                if ((qrframe[x + width * y] && qrframe[(x + 1) + width * y]
                     && qrframe[x + width * (y + 1)] && qrframe[(x + 1) + width * (y + 1)]) // all black
                    || !(qrframe[x + width * y] || qrframe[(x + 1) + width * y]
                         || qrframe[x + width * (y + 1)] || qrframe[(x + 1) + width * (y + 1)])) // all white
                    thisbad += N2;

        // X runs
        for (y = 0; y < width; y++) {
            rlens[0] = 0;
            for (h = b = x = 0; x < width; x++) {
                if ((b1 = qrframe[x + width * y]) == b)
                    rlens[h]++;
                else
                    rlens[++h] = 1;
                b = b1;
                bw += b ? 1 : -1;
            }
            thisbad += badruns(h);
        }

        // black/white imbalance
        if (bw < 0)
            bw = -bw;

        var big = bw;
        var count = 0;
        big += big << 2;
        big <<= 1;
        while (big > width * width)
            big -= width * width, count++;
        thisbad += count * N4;

        // Y runs
        for (x = 0; x < width; x++) {
            rlens[0] = 0;
            for (h = b = y = 0; y < width; y++) {
                if ((b1 = qrframe[x + width * y]) == b)
                    rlens[h]++;
                else
                    rlens[++h] = 1;
                b = b1;
            }
            thisbad += badruns(h);
        }
        return thisbad;
    }

    function genframe(instring)
    {
        var x, y, k, t, v, i, j, m;

    // find the smallest version that fits the string
        t = instring.length;
        version = 0;
        do {
            version++;
            k = (ecclevel - 1) * 4 + (version - 1) * 16;
            neccblk1 = eccblocks[k++];
            neccblk2 = eccblocks[k++];
            datablkw = eccblocks[k++];
            eccblkwid = eccblocks[k];
            k = datablkw * (neccblk1 + neccblk2) + neccblk2 - 3 + (version <= 9);
            if (t <= k)
                break;
        } while (version < 40);

    // FIXME - insure that it fits insted of being truncated
        width = 17 + 4 * version;

    // allocate, clear and setup data structures
        v = datablkw + (datablkw + eccblkwid) * (neccblk1 + neccblk2) + neccblk2;
        for( t = 0; t < v; t++ )
            eccbuf[t] = 0;
        strinbuf = instring.slice(0);

        for( t = 0; t < width * width; t++ )
            qrframe[t] = 0;

        for( t = 0 ; t < (width * (width + 1) + 1) / 2; t++)
            framask[t] = 0;

    // insert finders - black to frame, white to mask
        for (t = 0; t < 3; t++) {
            k = 0;
            y = 0;
            if (t == 1)
                k = (width - 7);
            if (t == 2)
                y = (width - 7);
            qrframe[(y + 3) + width * (k + 3)] = 1;
            for (x = 0; x < 6; x++) {
                qrframe[(y + x) + width * k] = 1;
                qrframe[y + width * (k + x + 1)] = 1;
                qrframe[(y + 6) + width * (k + x)] = 1;
                qrframe[(y + x + 1) + width * (k + 6)] = 1;
            }
            for (x = 1; x < 5; x++) {
                setmask(y + x, k + 1);
                setmask(y + 1, k + x + 1);
                setmask(y + 5, k + x);
                setmask(y + x + 1, k + 5);
            }
            for (x = 2; x < 4; x++) {
                qrframe[(y + x) + width * (k + 2)] = 1;
                qrframe[(y + 2) + width * (k + x + 1)] = 1;
                qrframe[(y + 4) + width * (k + x)] = 1;
                qrframe[(y + x + 1) + width * (k + 4)] = 1;
            }
        }

    // alignment blocks
        if (version > 1) {
            t = adelta[version];
            y = width - 7;
            for (;;) {
                x = width - 7;
                while (x > t - 3) {
                    putalign(x, y);
                    if (x < t)
                        break;
                    x -= t;
                }
                if (y <= t + 9)
                    break;
                y -= t;
                putalign(6, y);
                putalign(y, 6);
            }
        }

    // single black
        qrframe[8 + width * (width - 8)] = 1;

    // timing gap - mask only
        for (y = 0; y < 7; y++) {
            setmask(7, y);
            setmask(width - 8, y);
            setmask(7, y + width - 7);
        }
        for (x = 0; x < 8; x++) {
            setmask(x, 7);
            setmask(x + width - 8, 7);
            setmask(x, width - 8);
        }

    // reserve mask-format area
        for (x = 0; x < 9; x++)
            setmask(x, 8);
        for (x = 0; x < 8; x++) {
            setmask(x + width - 8, 8);
            setmask(8, x);
        }
        for (y = 0; y < 7; y++)
            setmask(8, y + width - 7);

    // timing row/col
        for (x = 0; x < width - 14; x++)
            if (x & 1) {
                setmask(8 + x, 6);
                setmask(6, 8 + x);
            }
            else {
                qrframe[(8 + x) + width * 6] = 1;
                qrframe[6 + width * (8 + x)] = 1;
            }

    // version block
        if (version > 6) {
            t = vpat[version - 7];
            k = 17;
            for (x = 0; x < 6; x++)
                for (y = 0; y < 3; y++, k--)
                    if (1 & (k > 11 ? version >> (k - 12) : t >> k)) {
                        qrframe[(5 - x) + width * (2 - y + width - 11)] = 1;
                        qrframe[(2 - y + width - 11) + width * (5 - x)] = 1;
                    }
            else {
                setmask(5 - x, 2 - y + width - 11);
                setmask(2 - y + width - 11, 5 - x);
            }
        }

    // sync mask bits - only set above for white spaces, so add in black bits
        for (y = 0; y < width; y++)
            for (x = 0; x <= y; x++)
                if (qrframe[x + width * y])
                    setmask(x, y);

    // convert string to bitstream
    // 8 bit data to QR-coded 8 bit data (numeric or alphanum, or kanji not supported)
        v = strinbuf.length;

    // string to array
        for( i = 0 ; i < v; i++ )
            eccbuf[i] = strinbuf.charCodeAt(i);
        strinbuf = eccbuf.slice(0);

    // calculate max string length
        x = datablkw * (neccblk1 + neccblk2) + neccblk2;
        if (v >= x - 2) {
            v = x - 2;
            if (version > 9)
                v--;
        }

    // shift and repack to insert length prefix
        i = v;
        if (version > 9) {
            strinbuf[i + 2] = 0;
            strinbuf[i + 3] = 0;
            while (i--) {
                t = strinbuf[i];
                strinbuf[i + 3] |= 255 & (t << 4);
                strinbuf[i + 2] = t >> 4;
            }
            strinbuf[2] |= 255 & (v << 4);
            strinbuf[1] = v >> 4;
            strinbuf[0] = 0x40 | (v >> 12);
        }
        else {
            strinbuf[i + 1] = 0;
            strinbuf[i + 2] = 0;
            while (i--) {
                t = strinbuf[i];
                strinbuf[i + 2] |= 255 & (t << 4);
                strinbuf[i + 1] = t >> 4;
            }
            strinbuf[1] |= 255 & (v << 4);
            strinbuf[0] = 0x40 | (v >> 4);
        }
    // fill to end with pad pattern
        i = v + 3 - (version < 10);
        while (i < x) {
            strinbuf[i++] = 0xec;
            // buffer has room    if (i == x)      break;
            strinbuf[i++] = 0x11;
        }

    // calculate and append ECC

    // calculate generator polynomial
        genpoly[0] = 1;
        for (i = 0; i < eccblkwid; i++) {
            genpoly[i + 1] = 1;
            for (j = i; j > 0; j--)
                genpoly[j] = genpoly[j]
                ? genpoly[j - 1] ^ gexp[modnn(glog[genpoly[j]] + i)] : genpoly[j - 1];
            genpoly[0] = gexp[modnn(glog[genpoly[0]] + i)];
        }
        for (i = 0; i <= eccblkwid; i++)
            genpoly[i] = glog[genpoly[i]]; // use logs for genpoly[] to save calc step

    // append ecc to data buffer
        k = x;
        y = 0;
        for (i = 0; i < neccblk1; i++) {
            appendrs(y, datablkw, k, eccblkwid);
            y += datablkw;
            k += eccblkwid;
        }
        for (i = 0; i < neccblk2; i++) {
            appendrs(y, datablkw + 1, k, eccblkwid);
            y += datablkw + 1;
            k += eccblkwid;
        }
    // interleave blocks
        y = 0;
        for (i = 0; i < datablkw; i++) {
            for (j = 0; j < neccblk1; j++)
                eccbuf[y++] = strinbuf[i + j * datablkw];
            for (j = 0; j < neccblk2; j++)
                eccbuf[y++] = strinbuf[(neccblk1 * datablkw) + i + (j * (datablkw + 1))];
        }
        for (j = 0; j < neccblk2; j++)
            eccbuf[y++] = strinbuf[(neccblk1 * datablkw) + i + (j * (datablkw + 1))];
        for (i = 0; i < eccblkwid; i++)
            for (j = 0; j < neccblk1 + neccblk2; j++)
                eccbuf[y++] = strinbuf[x + i + j * eccblkwid];
        strinbuf = eccbuf;

    // pack bits into frame avoiding masked area.
        x = y = width - 1;
        k = v = 1;         // up, minus
        /* inteleaved data and ecc codes */
        m = (datablkw + eccblkwid) * (neccblk1 + neccblk2) + neccblk2;
        for (i = 0; i < m; i++) {
            t = strinbuf[i];
            for (j = 0; j < 8; j++, t <<= 1) {
                if (0x80 & t)
                    qrframe[x + width * y] = 1;
                do {        // find next fill position
                    if (v)
                        x--;
                    else {
                        x++;
                        if (k) {
                            if (y != 0)
                                y--;
                            else {
                                x -= 2;
                                k = !k;
                                if (x == 6) {
                                    x--;
                                    y = 9;
                                }
                            }
                        }
                        else {
                            if (y != width - 1)
                                y++;
                            else {
                                x -= 2;
                                k = !k;
                                if (x == 6) {
                                    x--;
                                    y -= 8;
                                }
                            }
                        }
                    }
                    v = !v;
                } while (ismasked(x, y));
            }
        }

    // save pre-mask copy of frame
        strinbuf = qrframe.slice(0);
        t = 0;           // best
        y = 30000;         // demerit
    // for instead of while since in original arduino code
    // if an early mask was "good enough" it wouldn't try for a better one
    // since they get more complex and take longer.
        for (k = 0; k < 8; k++) {
            applymask(k);      // returns black-white imbalance
            x = badcheck();
            if (x < y) { // current mask better than previous best?
                y = x;
                t = k;
            }
            if (t == 7)
                break;       // don't increment i to a void redoing mask
            qrframe = strinbuf.slice(0); // reset for next pass
        }
        if (t != k)         // redo best mask - none good enough, last wasn't t
            applymask(t);

    // add in final mask/ecclevel bytes
        y = fmtword[t + ((ecclevel - 1) << 3)];
        // low byte
        for (k = 0; k < 8; k++, y >>= 1)
            if (y & 1) {
                qrframe[(width - 1 - k) + width * 8] = 1;
                if (k < 6)
                    qrframe[8 + width * k] = 1;
                else
                    qrframe[8 + width * (k + 1)] = 1;
            }
        // high byte
        for (k = 0; k < 7; k++, y >>= 1)
            if (y & 1) {
                qrframe[8 + width * (width - 7 + k)] = 1;
                if (k)
                    qrframe[(6 - k) + width * 8] = 1;
                else
                    qrframe[7 + width * 8] = 1;
            }

    // return image
        return qrframe;
    }

    var _canvas = null,
        _size = null;

    var api = {

        get ecclevel () {
            return ecclevel;
        },

        set ecclevel (val) {
            ecclevel = val;
        },

        get size () {
            return _size;
        },

        set size (val) {
            _size = val
        },

        get canvas () {
            return _canvas;
        },

        set canvas (el) {
            _canvas = el;
        },

        getFrame: function (string) {
            return genframe(string);
        },

        draw: function (string, canvas, size, ecc) {

            ecclevel = ecc || ecclevel;
            canvas = canvas || _canvas;

            if (!canvas) {
                console.warn('No canvas provided to draw QR code in!')
                return;
            }

            size = size || _size || Math.min(canvas.width, canvas.height);

            var frame = genframe(string),
                ctx = canvas.ctx,
                px = Math.round(size / (width + 8));

            var roundedSize = px * (width + 8),
                offset = Math.floor((size - roundedSize) / 2);

            size = roundedSize;

            ctx.clearRect(0, 0, canvas.width, canvas.height);
            ctx.setFillStyle('#000000');
            for (var i = 0; i < width; i++) {
                for (var j = 0; j < width; j++) {
                    if (frame[j * width + i]) {
                        ctx.fillRect(px * (4 + i) + offset, px * (4 + j) + offset, px, px);
                    }
                }
            }
            ctx.draw();
        }
    }

    module.exports = {
        api: api
    }

})()