一、看下效果图

二、废话不多说，直接上代码
1.页面增加存放二维码的标签

<canvas class="bar_code" canvas-id="Qrcode"></canvas>

2.引入qrcode.js，后面会放上

import qrCode from "../../utils/qrcode.js"

3.在自己的methods中写入生成二维码的方法

qrCode.api.draw(this.info.CardNo,{ctx:uni.createCanvasContext('Qrcode'), width: this.convert_length(300), height: this.convert_length(300)});

其中api.draw为qrcode.js的导出函数，需要传入四个参数。
第一个参数为用户卡的编号，我自己定义的是需要将用户卡编号转成二维码
第二个参数是一个对象，对象中的第一个参数为创建 canvas 绘图上下文并且制定了创建canvasId，这里的canvasId为Qrcode，需要与第一步骤的id对上；
对象的第二、三个参数分别为宽度、高度，可以根据自己需求来定
这样我们的二维码就成功生成了
三、qrcode.js 文件的代码，本来想上传js文件，后来没找到地方上传，干脆把代码直接上了

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
    }

})()