Taro+vue微信小程序根据字符串生成二维码图片，点击弹出图片，长按保存（可用！！！）

Taro+vue微信小程序根据字符串生成二维码图片

效果：页面加载时生成二维码，点击二维码弹出图片，长按图片可保存。

1. 工具类qrcode.js

!(function () {

    // alignment pattern
    var adelta = [
        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
    ];

    // 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 qrframe;
    }




    var _canvas = 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);
        },
        //这里的utf16to8(str)是对Text中的字符串进行转码，让其支持中文
        utf16to8: function (str) {
            var out, i, len, c;

            out = "";
            len = str.length;
            for (i = 0; i < len; i++) {
                c = str.charCodeAt(i);
                if ((c >= 0x0001) && (c <= 0x007F)) {
                    out += str.charAt(i);
                } else if (c > 0x07FF) {
                    out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
                    out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
                    out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
                } else {
                    out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
                    out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
                }
            }
            return out;
        },
        /**
         * 新增$this参数，传入组件的this,兼容在组件中生成
         */
        draw: function (str, canvas, cavW, cavH, $this, cb = function () { }, ecc) {
            var that = this;
            ecclevel = ecc || ecclevel;
            canvas = canvas || _canvas;
            if (!canvas) {
                console.warn('No canvas provided to draw QR code in!')
                return;
            }

            var size = Math.min(cavW, cavH);
            str = that.utf16to8(str); //增加中文显示

            var frame = that.getFrame(str),
                // 组件中生成qrcode需要绑定this 
                ctx = wx.createCanvasContext(canvas, $this),
                px = Math.round(size / (width + 8));
            var roundedSize = px * (width + 8),
                offset = Math.floor((size - roundedSize) / 2);
            size = roundedSize;
            //ctx.clearRect(0, 0, cavW, cavW);
            ctx.setFillStyle('#ff9933')
            ctx.fillRect(0, 0, cavW, cavW);
            ctx.setFillStyle('#ffffff');
            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);
                    }
                }
            }
            // // 字体
            // ctx.setFontSize(14)
            // // 颜色
            // ctx.setFillStyle("#ffffff")
            // ctx.setTextAlign('center')
            // ctx.fillText('title', size*0.5, size)
            //--增加绘制完成回调
            ctx.draw(false, function () {
                cb();
            })

        }
    }
    module.exports = {
        api
    }
})();

2.qrCode组件代码

<template>
    
    <view class='container'>
        <image :style="'width: '+qrWidth+'rpx;height: '+qrWidth+'rpx;'" @tap="previewImg" mode="scaleToFill" :src="imagePath">image>
    view>
    
    <view class="canvas-box">
        <canvas hidden="{{canvasHidden}}" :style="'width: '+qrWidth+'rpx;height: '+qrWidth+'rpx;background:#f1f1f1;'" canvas-id="mycanvas" />
    view>
template>

<script>
var QR = require("../../src/utils/qrcode.js")
const vueConfig = require('../../config/config.js')

export default {
    name: 'Index',
    data () {
        return {
            weChatPath: vueConfig.weChatPath,
            activityId: 891,
            canvasHidden: false,
            imagePath: '',
        }
    },
    props: {
        qrWidth: {
            type: Number,
            default: () => 686,
        },
    },
    mounted () {
        this.$nextTick(() => {
            var size = this.setCanvasSize(); //动态设置画布大小
            // 二维码内容（一个小程序的页面链接：https://www.**.com:8080?activity=）
            var url = this.weChatPath + this.activityId
            this.createQrCode(url, "mycanvas", size.w, size.h);
        })
    },
    methods: {
        //适配不同屏幕大小的canvas
        setCanvasSize: function () {
            var size = {};
            try {
                var res = wx.getSystemInfoSync();
                var scale = 750 / this.qrWidth; //不同屏幕下canvas的适配比例；设计稿是750宽 686是因为样式wxss文件中设置的大小
                var width = res.windowWidth / scale;
                var height = width; //canvas画布为正方形
                size.w = width;
                size.h = height;
            } catch (e) {
                // Do something when catch error
                console.log("获取设备信息失败" + e);
            }
            return size;
        },
        /**
         * 绘制二维码图片
         */
        createQrCode: function (url, canvasId, cavW, cavH) {
            //调用插件中的draw方法，绘制二维码图片
            QR.api.draw(url, canvasId, cavW, cavH, '');
            setTimeout(() => {
                this.canvasToTempImage();
            }, 1000);
        },
        /**
         * 获取临时缓存照片路径，存入data中
         */
        canvasToTempImage: function () {
            var that = this;
            //把当前画布指定区域的内容导出生成指定大小的图片，并返回文件路径。
            wx.canvasToTempFilePath({
                canvasId: 'mycanvas',
                success: function (res) {
                    var tempFilePath = res.tempFilePath;
                    console.log(tempFilePath);
                    that.imagePath = tempFilePath
                },
                fail: function (res) {
                    console.log(res);
                }
            });
        },
        /**
         * 点击图片进行预览
         */
        previewImg: function (e) {
            var img = this.imagePath;
            console.log(img);
            wx.previewImage({
                current: img, // 当前显示图片的http链接
                urls: [img] // 需要预览的图片http链接列表
            });
        },
    },
}
script>

<style>
.container {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
}

.container image {
    background-color: #f9f9f9;
}

.canvas-box {
    position: fixed;
    top: 999999rpx;
    left: 0;
}
style>

3.组件的使用

<template>
   <qrCode :qrWidth="200">qrCode>
template>

<script>
//引用Taro控件
import qrCode from '../../components/qrCode.vue'

export default {
    name: 'Index',
    data () {
        return {
          
        }
    },
    components: {
        qrCode
    },
    mounted () {

    },
    methods: {
      
    },
}
script>

<style>

style>

借鉴了一个大佬的文章https://www.zhangshengrong.com/p/q0arZ9J4ax/#google_vignette