canvas画二维码并生成图片（微信原生可用，其余的平台可以自行尝试）

效果展示：

1.首先创建weapp.qrcode.esm.js文件，将以下代码复制上去（适用于微信原生小程序），建议创在utils文件下

/**
 * weapp.qrcode.js v1.0.0 (https://github.com/yingye/weapp-qrcode#readme)
 */

(function (global, factory) {
	typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
	typeof define === 'function' && define.amd ? define(factory) :
	(global.drawQrcode = factory());
}(this, (function () { 'use strict';

var hasOwn = Object.prototype.hasOwnProperty;
var toStr = Object.prototype.toString;
var defineProperty = Object.defineProperty;
var gOPD = Object.getOwnPropertyDescriptor;

var isArray = function isArray(arr) {
	if (typeof Array.isArray === 'function') {
		return Array.isArray(arr);
	}

	return toStr.call(arr) === '[object Array]';
};

var isPlainObject = function isPlainObject(obj) {
	if (!obj || toStr.call(obj) !== '[object Object]') {
		return false;
	}

	var hasOwnConstructor = hasOwn.call(obj, 'constructor');
	var hasIsPrototypeOf = obj.constructor && obj.constructor.prototype && hasOwn.call(obj.constructor.prototype, 'isPrototypeOf');
	// Not own constructor property must be Object
	if (obj.constructor && !hasOwnConstructor && !hasIsPrototypeOf) {
		return false;
	}

	// Own properties are enumerated firstly, so to speed up,
	// if last one is own, then all properties are own.
	var key;
	for (key in obj) { /**/ }

	return typeof key === 'undefined' || hasOwn.call(obj, key);
};

// If name is '__proto__', and Object.defineProperty is available, define __proto__ as an own property on target
var setProperty = function setProperty(target, options) {
	if (defineProperty && options.name === '__proto__') {
		defineProperty(target, options.name, {
			enumerable: true,
			configurable: true,
			value: options.newValue,
			writable: true
		});
	} else {
		target[options.name] = options.newValue;
	}
};

// Return undefined instead of __proto__ if '__proto__' is not an own property
var getProperty = function getProperty(obj, name) {
	if (name === '__proto__') {
		if (!hasOwn.call(obj, name)) {
			return void 0;
		} else if (gOPD) {
			// In early versions of node, obj['__proto__'] is buggy when obj has
			// __proto__ as an own property. Object.getOwnPropertyDescriptor() works.
			return gOPD(obj, name).value;
		}
	}

	return obj[name];
};

var extend = function extend() {
	var options, name, src, copy, copyIsArray, clone;
	var target = arguments[0];
	var i = 1;
	var length = arguments.length;
	var deep = false;

	// Handle a deep copy situation
	if (typeof target === 'boolean') {
		deep = target;
		target = arguments[1] || {};
		// skip the boolean and the target
		i = 2;
	}
	if (target == null || (typeof target !== 'object' && typeof target !== 'function')) {
		target = {};
	}

	for (; i < length; ++i) {
		options = arguments[i];
		// Only deal with non-null/undefined values
		if (options != null) {
			// Extend the base object
			for (name in options) {
				src = getProperty(target, name);
				copy = getProperty(options, name);

				// Prevent never-ending loop
				if (target !== copy) {
					// Recurse if we're merging plain objects or arrays
					if (deep && copy && (isPlainObject(copy) || (copyIsArray = isArray(copy)))) {
						if (copyIsArray) {
							copyIsArray = false;
							clone = src && isArray(src) ? src : [];
						} else {
							clone = src && isPlainObject(src) ? src : {};
						}

						// Never move original objects, clone them
						setProperty(target, { name: name, newValue: extend(deep, clone, copy) });

					// Don't bring in undefined values
					} else if (typeof copy !== 'undefined') {
						setProperty(target, { name: name, newValue: copy });
					}
				}
			}
		}
	}

	// Return the modified object
	return target;
};

//---------------------------------------------------------------------
// QRCode for JavaScript
//
// Copyright (c) 2009 Kazuhiko Arase
//
// URL: http://www.d-project.com/
//
// Licensed under the MIT license:
//   http://www.opensource.org/licenses/mit-license.php
//
// The word "QR Code" is registered trademark of 
// DENSO WAVE INCORPORATED
//   http://www.denso-wave.com/qrcode/faqpatent-e.html
//
//---------------------------------------------------------------------

//---------------------------------------------------------------------
// QR8bitByte
//---------------------------------------------------------------------

function QR8bitByte(data) {
  this.mode = QRMode.MODE_8BIT_BYTE;
  this.data = data;
}

QR8bitByte.prototype = {

  getLength: function (buffer) {
    return this.data.length;
  },

  write: function (buffer) {
    for (var i = 0; i < this.data.length; i++) {
      // not JIS ...
      buffer.put(this.data.charCodeAt(i), 8);
    }
  }
};

//---------------------------------------------------------------------
// QRCode
//---------------------------------------------------------------------

function QRCode(typeNumber, errorCorrectLevel) {
  this.typeNumber = typeNumber;
  this.errorCorrectLevel = errorCorrectLevel;
  this.modules = null;
  this.moduleCount = 0;
  this.dataCache = null;
  this.dataList = new Array();
}

QRCode.prototype = {

  addData: function (data) {
    var newData = new QR8bitByte(data);
    this.dataList.push(newData);
    this.dataCache = null;
  },

  isDark: function (row, col) {
    if (row < 0 || this.moduleCount <= row || col < 0 || this.moduleCount <= col) {
      throw new Error(row + "," + col);
    }
    return this.modules[row][col];
  },

  getModuleCount: function () {
    return this.moduleCount;
  },

  make: function () {
    // Calculate automatically typeNumber if provided is < 1
    if (this.typeNumber < 1) {
      var typeNumber = 1;
      for (typeNumber = 1; typeNumber < 40; typeNumber++) {
        var rsBlocks = QRRSBlock.getRSBlocks(typeNumber, this.errorCorrectLevel);

        var buffer = new QRBitBuffer();
        var totalDataCount = 0;
        for (var i = 0; i < rsBlocks.length; i++) {
          totalDataCount += rsBlocks[i].dataCount;
        }

        for (var i = 0; i < this.dataList.length; i++) {
          var data = this.dataList[i];
          buffer.put(data.mode, 4);
          buffer.put(data.getLength(), QRUtil.getLengthInBits(data.mode, typeNumber));
          data.write(buffer);
        }
        if (buffer.getLengthInBits() <= totalDataCount * 8) break;
      }
      this.typeNumber = typeNumber;
    }
    this.makeImpl(false, this.getBestMaskPattern());
  },

  makeImpl: function (test, maskPattern) {

    this.moduleCount = this.typeNumber * 4 + 17;
    this.modules = new Array(this.moduleCount);

    for (var row = 0; row < this.moduleCount; row++) {

      this.modules[row] = new Array(this.moduleCount);

      for (var col = 0; col < this.moduleCount; col++) {
        this.modules[row][col] = null; //(col + row) % 3;
      }
    }

    this.setupPositionProbePattern(0, 0);
    this.setupPositionProbePattern(this.moduleCount - 7, 0);
    this.setupPositionProbePattern(0, this.moduleCount - 7);
    this.setupPositionAdjustPattern();
    this.setupTimingPattern();
    this.setupTypeInfo(test, maskPattern);

    if (this.typeNumber >= 7) {
      this.setupTypeNumber(test);
    }

    if (this.dataCache == null) {
      this.dataCache = QRCode.createData(this.typeNumber, this.errorCorrectLevel, this.dataList);
    }

    this.mapData(this.dataCache, maskPattern);
  },

  setupPositionProbePattern: function (row, col) {

    for (var r = -1; r <= 7; r++) {

      if (row + r <= -1 || this.moduleCount <= row + r) continue;

      for (var c = -1; c <= 7; c++) {

        if (col + c <= -1 || this.moduleCount <= col + c) continue;

        if (0 <= r && r <= 6 && (c == 0 || c == 6) || 0 <= c && c <= 6 && (r == 0 || r == 6) || 2 <= r && r <= 4 && 2 <= c && c <= 4) {
          this.modules[row + r][col + c] = true;
        } else {
          this.modules[row + r][col + c] = false;
        }
      }
    }
  },

  getBestMaskPattern: function () {

    var minLostPoint = 0;
    var pattern = 0;

    for (var i = 0; i < 8; i++) {

      this.makeImpl(true, i);

      var lostPoint = QRUtil.getLostPoint(this);

      if (i == 0 || minLostPoint > lostPoint) {
        minLostPoint = lostPoint;
        pattern = i;
      }
    }

    return pattern;
  },

  createMovieClip: function (target_mc, instance_name, depth) {

    var qr_mc = target_mc.createEmptyMovieClip(instance_name, depth);
    var cs = 1;

    this.make();

    for (var row = 0; row < this.modules.length; row++) {

      var y = row * cs;

      for (var col = 0; col < this.modules[row].length; col++) {

        var x = col * cs;
        var dark = this.modules[row][col];

        if (dark) {
          qr_mc.beginFill(0, 100);
          qr_mc.moveTo(x, y);
          qr_mc.lineTo(x + cs, y);
          qr_mc.lineTo(x + cs, y + cs);
          qr_mc.lineTo(x, y + cs);
          qr_mc.endFill();
        }
      }
    }

    return qr_mc;
  },

  setupTimingPattern: function () {

    for (var r = 8; r < this.moduleCount - 8; r++) {
      if (this.modules[r][6] != null) {
        continue;
      }
      this.modules[r][6] = r % 2 == 0;
    }

    for (var c = 8; c < this.moduleCount - 8; c++) {
      if (this.modules[6][c] != null) {
        continue;
      }
      this.modules[6][c] = c % 2 == 0;
    }
  },

  setupPositionAdjustPattern: function () {

    var pos = QRUtil.getPatternPosition(this.typeNumber);

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

      for (var j = 0; j < pos.length; j++) {

        var row = pos[i];
        var col = pos[j];

        if (this.modules[row][col] != null) {
          continue;
        }

        for (var r = -2; r <= 2; r++) {

          for (var c = -2; c <= 2; c++) {

            if (r == -2 || r == 2 || c == -2 || c == 2 || r == 0 && c == 0) {
              this.modules[row + r][col + c] = true;
            } else {
              this.modules[row + r][col + c] = false;
            }
          }
        }
      }
    }
  },

  setupTypeNumber: function (test) {

    var bits = QRUtil.getBCHTypeNumber(this.typeNumber);

    for (var i = 0; i < 18; i++) {
      var mod = !test && (bits >> i & 1) == 1;
      this.modules[Math.floor(i / 3)][i % 3 + this.moduleCount - 8 - 3] = mod;
    }

    for (var i = 0; i < 18; i++) {
      var mod = !test && (bits >> i & 1) == 1;
      this.modules[i % 3 + this.moduleCount - 8 - 3][Math.floor(i / 3)] = mod;
    }
  },

  setupTypeInfo: function (test, maskPattern) {

    var data = this.errorCorrectLevel << 3 | maskPattern;
    var bits = QRUtil.getBCHTypeInfo(data);

    // vertical   
    for (var i = 0; i < 15; i++) {

      var mod = !test && (bits >> i & 1) == 1;

      if (i < 6) {
        this.modules[i][8] = mod;
      } else if (i < 8) {
        this.modules[i + 1][8] = mod;
      } else {
        this.modules[this.moduleCount - 15 + i][8] = mod;
      }
    }

    // horizontal
    for (var i = 0; i < 15; i++) {

      var mod = !test && (bits >> i & 1) == 1;

      if (i < 8) {
        this.modules[8][this.moduleCount - i - 1] = mod;
      } else if (i < 9) {
        this.modules[8][15 - i - 1 + 1] = mod;
      } else {
        this.modules[8][15 - i - 1] = mod;
      }
    }

    // fixed module
    this.modules[this.moduleCount - 8][8] = !test;
  },

  mapData: function (data, maskPattern) {

    var inc = -1;
    var row = this.moduleCount - 1;
    var bitIndex = 7;
    var byteIndex = 0;

    for (var col = this.moduleCount - 1; col > 0; col -= 2) {

      if (col == 6) col--;

      while (true) {

        for (var c = 0; c < 2; c++) {

          if (this.modules[row][col - c] == null) {

            var dark = false;

            if (byteIndex < data.length) {
              dark = (data[byteIndex] >>> bitIndex & 1) == 1;
            }

            var mask = QRUtil.getMask(maskPattern, row, col - c);

            if (mask) {
              dark = !dark;
            }

            this.modules[row][col - c] = dark;
            bitIndex--;

            if (bitIndex == -1) {
              byteIndex++;
              bitIndex = 7;
            }
          }
        }

        row += inc;

        if (row < 0 || this.moduleCount <= row) {
          row -= inc;
          inc = -inc;
          break;
        }
      }
    }
  }

};

QRCode.PAD0 = 0xEC;
QRCode.PAD1 = 0x11;

QRCode.createData = function (typeNumber, errorCorrectLevel, dataList) {

  var rsBlocks = QRRSBlock.getRSBlocks(typeNumber, errorCorrectLevel);

  var buffer = new QRBitBuffer();

  for (var i = 0; i < dataList.length; i++) {
    var data = dataList[i];
    buffer.put(data.mode, 4);
    buffer.put(data.getLength(), QRUtil.getLengthInBits(data.mode, typeNumber));
    data.write(buffer);
  }

  // calc num max data.
  var totalDataCount = 0;
  for (var i = 0; i < rsBlocks.length; i++) {
    totalDataCount += rsBlocks[i].dataCount;
  }

  if (buffer.getLengthInBits() > totalDataCount * 8) {
    throw new Error("code length overflow. (" + buffer.getLengthInBits() + ">" + totalDataCount * 8 + ")");
  }

  // end code
  if (buffer.getLengthInBits() + 4 <= totalDataCount * 8) {
    buffer.put(0, 4);
  }

  // padding
  while (buffer.getLengthInBits() % 8 != 0) {
    buffer.putBit(false);
  }

  // padding
  while (true) {

    if (buffer.getLengthInBits() >= totalDataCount * 8) {
      break;
    }
    buffer.put(QRCode.PAD0, 8);

    if (buffer.getLengthInBits() >= totalDataCount * 8) {
      break;
    }
    buffer.put(QRCode.PAD1, 8);
  }

  return QRCode.createBytes(buffer, rsBlocks);
};

QRCode.createBytes = function (buffer, rsBlocks) {

  var offset = 0;

  var maxDcCount = 0;
  var maxEcCount = 0;

  var dcdata = new Array(rsBlocks.length);
  var ecdata = new Array(rsBlocks.length);

  for (var r = 0; r < rsBlocks.length; r++) {

    var dcCount = rsBlocks[r].dataCount;
    var ecCount = rsBlocks[r].totalCount - dcCount;

    maxDcCount = Math.max(maxDcCount, dcCount);
    maxEcCount = Math.max(maxEcCount, ecCount);

    dcdata[r] = new Array(dcCount);

    for (var i = 0; i < dcdata[r].length; i++) {
      dcdata[r][i] = 0xff & buffer.buffer[i + offset];
    }
    offset += dcCount;

    var rsPoly = QRUtil.getErrorCorrectPolynomial(ecCount);
    var rawPoly = new QRPolynomial(dcdata[r], rsPoly.getLength() - 1);

    var modPoly = rawPoly.mod(rsPoly);
    ecdata[r] = new Array(rsPoly.getLength() - 1);
    for (var i = 0; i < ecdata[r].length; i++) {
      var modIndex = i + modPoly.getLength() - ecdata[r].length;
      ecdata[r][i] = modIndex >= 0 ? modPoly.get(modIndex) : 0;
    }
  }

  var totalCodeCount = 0;
  for (var i = 0; i < rsBlocks.length; i++) {
    totalCodeCount += rsBlocks[i].totalCount;
  }

  var data = new Array(totalCodeCount);
  var index = 0;

  for (var i = 0; i < maxDcCount; i++) {
    for (var r = 0; r < rsBlocks.length; r++) {
      if (i < dcdata[r].length) {
        data[index++] = dcdata[r][i];
      }
    }
  }

  for (var i = 0; i < maxEcCount; i++) {
    for (var r = 0; r < rsBlocks.length; r++) {
      if (i < ecdata[r].length) {
        data[index++] = ecdata[r][i];
      }
    }
  }

  return data;
};

//---------------------------------------------------------------------
// QRMode
//---------------------------------------------------------------------

var QRMode = {
  MODE_NUMBER: 1 << 0,
  MODE_ALPHA_NUM: 1 << 1,
  MODE_8BIT_BYTE: 1 << 2,
  MODE_KANJI: 1 << 3
};

//---------------------------------------------------------------------
// QRErrorCorrectLevel
//---------------------------------------------------------------------

var QRErrorCorrectLevel = {
  L: 1,
  M: 0,
  Q: 3,
  H: 2
};

//---------------------------------------------------------------------
// QRMaskPattern
//---------------------------------------------------------------------

var QRMaskPattern = {
  PATTERN000: 0,
  PATTERN001: 1,
  PATTERN010: 2,
  PATTERN011: 3,
  PATTERN100: 4,
  PATTERN101: 5,
  PATTERN110: 6,
  PATTERN111: 7
};

//---------------------------------------------------------------------
// QRUtil
//---------------------------------------------------------------------

var QRUtil = {

  PATTERN_POSITION_TABLE: [[], [6, 18], [6, 22], [6, 26], [6, 30], [6, 34], [6, 22, 38], [6, 24, 42], [6, 26, 46], [6, 28, 50], [6, 30, 54], [6, 32, 58], [6, 34, 62], [6, 26, 46, 66], [6, 26, 48, 70], [6, 26, 50, 74], [6, 30, 54, 78], [6, 30, 56, 82], [6, 30, 58, 86], [6, 34, 62, 90], [6, 28, 50, 72, 94], [6, 26, 50, 74, 98], [6, 30, 54, 78, 102], [6, 28, 54, 80, 106], [6, 32, 58, 84, 110], [6, 30, 58, 86, 114], [6, 34, 62, 90, 118], [6, 26, 50, 74, 98, 122], [6, 30, 54, 78, 102, 126], [6, 26, 52, 78, 104, 130], [6, 30, 56, 82, 108, 134], [6, 34, 60, 86, 112, 138], [6, 30, 58, 86, 114, 142], [6, 34, 62, 90, 118, 146], [6, 30, 54, 78, 102, 126, 150], [6, 24, 50, 76, 102, 128, 154], [6, 28, 54, 80, 106, 132, 158], [6, 32, 58, 84, 110, 136, 162], [6, 26, 54, 82, 110, 138, 166], [6, 30, 58, 86, 114, 142, 170]],

  G15: 1 << 10 | 1 << 8 | 1 << 5 | 1 << 4 | 1 << 2 | 1 << 1 | 1 << 0,
  G18: 1 << 12 | 1 << 11 | 1 << 10 | 1 << 9 | 1 << 8 | 1 << 5 | 1 << 2 | 1 << 0,
  G15_MASK: 1 << 14 | 1 << 12 | 1 << 10 | 1 << 4 | 1 << 1,

  getBCHTypeInfo: function (data) {
    var d = data << 10;
    while (QRUtil.getBCHDigit(d) - QRUtil.getBCHDigit(QRUtil.G15) >= 0) {
      d ^= QRUtil.G15 << QRUtil.getBCHDigit(d) - QRUtil.getBCHDigit(QRUtil.G15);
    }
    return (data << 10 | d) ^ QRUtil.G15_MASK;
  },

  getBCHTypeNumber: function (data) {
    var d = data << 12;
    while (QRUtil.getBCHDigit(d) - QRUtil.getBCHDigit(QRUtil.G18) >= 0) {
      d ^= QRUtil.G18 << QRUtil.getBCHDigit(d) - QRUtil.getBCHDigit(QRUtil.G18);
    }
    return data << 12 | d;
  },

  getBCHDigit: function (data) {

    var digit = 0;

    while (data != 0) {
      digit++;
      data >>>= 1;
    }

    return digit;
  },

  getPatternPosition: function (typeNumber) {
    return QRUtil.PATTERN_POSITION_TABLE[typeNumber - 1];
  },

  getMask: function (maskPattern, i, j) {

    switch (maskPattern) {

      case QRMaskPattern.PATTERN000:
        return (i + j) % 2 == 0;
      case QRMaskPattern.PATTERN001:
        return i % 2 == 0;
      case QRMaskPattern.PATTERN010:
        return j % 3 == 0;
      case QRMaskPattern.PATTERN011:
        return (i + j) % 3 == 0;
      case QRMaskPattern.PATTERN100:
        return (Math.floor(i / 2) + Math.floor(j / 3)) % 2 == 0;
      case QRMaskPattern.PATTERN101:
        return i * j % 2 + i * j % 3 == 0;
      case QRMaskPattern.PATTERN110:
        return (i * j % 2 + i * j % 3) % 2 == 0;
      case QRMaskPattern.PATTERN111:
        return (i * j % 3 + (i + j) % 2) % 2 == 0;

      default:
        throw new Error("bad maskPattern:" + maskPattern);
    }
  },

  getErrorCorrectPolynomial: function (errorCorrectLength) {

    var a = new QRPolynomial([1], 0);

    for (var i = 0; i < errorCorrectLength; i++) {
      a = a.multiply(new QRPolynomial([1, QRMath.gexp(i)], 0));
    }

    return a;
  },

  getLengthInBits: function (mode, type) {

    if (1 <= type && type < 10) {

      // 1 - 9

      switch (mode) {
        case QRMode.MODE_NUMBER:
          return 10;
        case QRMode.MODE_ALPHA_NUM:
          return 9;
        case QRMode.MODE_8BIT_BYTE:
          return 8;
        case QRMode.MODE_KANJI:
          return 8;
        default:
          throw new Error("mode:" + mode);
      }
    } else if (type < 27) {

      // 10 - 26

      switch (mode) {
        case QRMode.MODE_NUMBER:
          return 12;
        case QRMode.MODE_ALPHA_NUM:
          return 11;
        case QRMode.MODE_8BIT_BYTE:
          return 16;
        case QRMode.MODE_KANJI:
          return 10;
        default:
          throw new Error("mode:" + mode);
      }
    } else if (type < 41) {

      // 27 - 40

      switch (mode) {
        case QRMode.MODE_NUMBER:
          return 14;
        case QRMode.MODE_ALPHA_NUM:
          return 13;
        case QRMode.MODE_8BIT_BYTE:
          return 16;
        case QRMode.MODE_KANJI:
          return 12;
        default:
          throw new Error("mode:" + mode);
      }
    } else {
      throw new Error("type:" + type);
    }
  },

  getLostPoint: function (qrCode) {

    var moduleCount = qrCode.getModuleCount();

    var lostPoint = 0;

    // LEVEL1

    for (var row = 0; row < moduleCount; row++) {

      for (var col = 0; col < moduleCount; col++) {

        var sameCount = 0;
        var dark = qrCode.isDark(row, col);

        for (var r = -1; r <= 1; r++) {

          if (row + r < 0 || moduleCount <= row + r) {
            continue;
          }

          for (var c = -1; c <= 1; c++) {

            if (col + c < 0 || moduleCount <= col + c) {
              continue;
            }

            if (r == 0 && c == 0) {
              continue;
            }

            if (dark == qrCode.isDark(row + r, col + c)) {
              sameCount++;
            }
          }
        }

        if (sameCount > 5) {
          lostPoint += 3 + sameCount - 5;
        }
      }
    }

    // LEVEL2

    for (var row = 0; row < moduleCount - 1; row++) {
      for (var col = 0; col < moduleCount - 1; col++) {
        var count = 0;
        if (qrCode.isDark(row, col)) count++;
        if (qrCode.isDark(row + 1, col)) count++;
        if (qrCode.isDark(row, col + 1)) count++;
        if (qrCode.isDark(row + 1, col + 1)) count++;
        if (count == 0 || count == 4) {
          lostPoint += 3;
        }
      }
    }

    // LEVEL3

    for (var row = 0; row < moduleCount; row++) {
      for (var col = 0; col < moduleCount - 6; col++) {
        if (qrCode.isDark(row, col) && !qrCode.isDark(row, col + 1) && qrCode.isDark(row, col + 2) && qrCode.isDark(row, col + 3) && qrCode.isDark(row, col + 4) && !qrCode.isDark(row, col + 5) && qrCode.isDark(row, col + 6)) {
          lostPoint += 40;
        }
      }
    }

    for (var col = 0; col < moduleCount; col++) {
      for (var row = 0; row < moduleCount - 6; row++) {
        if (qrCode.isDark(row, col) && !qrCode.isDark(row + 1, col) && qrCode.isDark(row + 2, col) && qrCode.isDark(row + 3, col) && qrCode.isDark(row + 4, col) && !qrCode.isDark(row + 5, col) && qrCode.isDark(row + 6, col)) {
          lostPoint += 40;
        }
      }
    }

    // LEVEL4

    var darkCount = 0;

    for (var col = 0; col < moduleCount; col++) {
      for (var row = 0; row < moduleCount; row++) {
        if (qrCode.isDark(row, col)) {
          darkCount++;
        }
      }
    }

    var ratio = Math.abs(100 * darkCount / moduleCount / moduleCount - 50) / 5;
    lostPoint += ratio * 10;

    return lostPoint;
  }

};

//---------------------------------------------------------------------
// QRMath
//---------------------------------------------------------------------

var QRMath = {

  glog: function (n) {

    if (n < 1) {
      throw new Error("glog(" + n + ")");
    }

    return QRMath.LOG_TABLE[n];
  },

  gexp: function (n) {

    while (n < 0) {
      n += 255;
    }

    while (n >= 256) {
      n -= 255;
    }

    return QRMath.EXP_TABLE[n];
  },

  EXP_TABLE: new Array(256),

  LOG_TABLE: new Array(256)

};

for (var i = 0; i < 8; i++) {
  QRMath.EXP_TABLE[i] = 1 << i;
}
for (var i = 8; i < 256; i++) {
  QRMath.EXP_TABLE[i] = QRMath.EXP_TABLE[i - 4] ^ QRMath.EXP_TABLE[i - 5] ^ QRMath.EXP_TABLE[i - 6] ^ QRMath.EXP_TABLE[i - 8];
}
for (var i = 0; i < 255; i++) {
  QRMath.LOG_TABLE[QRMath.EXP_TABLE[i]] = i;
}

//---------------------------------------------------------------------
// QRPolynomial
//---------------------------------------------------------------------

function QRPolynomial(num, shift) {

  if (num.length == undefined) {
    throw new Error(num.length + "/" + shift);
  }

  var offset = 0;

  while (offset < num.length && num[offset] == 0) {
    offset++;
  }

  this.num = new Array(num.length - offset + shift);
  for (var i = 0; i < num.length - offset; i++) {
    this.num[i] = num[i + offset];
  }
}

QRPolynomial.prototype = {

  get: function (index) {
    return this.num[index];
  },

  getLength: function () {
    return this.num.length;
  },

  multiply: function (e) {

    var num = new Array(this.getLength() + e.getLength() - 1);

    for (var i = 0; i < this.getLength(); i++) {
      for (var j = 0; j < e.getLength(); j++) {
        num[i + j] ^= QRMath.gexp(QRMath.glog(this.get(i)) + QRMath.glog(e.get(j)));
      }
    }

    return new QRPolynomial(num, 0);
  },

  mod: function (e) {

    if (this.getLength() - e.getLength() < 0) {
      return this;
    }

    var ratio = QRMath.glog(this.get(0)) - QRMath.glog(e.get(0));

    var num = new Array(this.getLength());

    for (var i = 0; i < this.getLength(); i++) {
      num[i] = this.get(i);
    }

    for (var i = 0; i < e.getLength(); i++) {
      num[i] ^= QRMath.gexp(QRMath.glog(e.get(i)) + ratio);
    }

    // recursive call
    return new QRPolynomial(num, 0).mod(e);
  }
};

//---------------------------------------------------------------------
// QRRSBlock
//---------------------------------------------------------------------

function QRRSBlock(totalCount, dataCount) {
  this.totalCount = totalCount;
  this.dataCount = dataCount;
}

QRRSBlock.RS_BLOCK_TABLE = [

// L
// M
// Q
// H

// 1
[1, 26, 19], [1, 26, 16], [1, 26, 13], [1, 26, 9],

// 2
[1, 44, 34], [1, 44, 28], [1, 44, 22], [1, 44, 16],

// 3
[1, 70, 55], [1, 70, 44], [2, 35, 17], [2, 35, 13],

// 4    
[1, 100, 80], [2, 50, 32], [2, 50, 24], [4, 25, 9],

// 5
[1, 134, 108], [2, 67, 43], [2, 33, 15, 2, 34, 16], [2, 33, 11, 2, 34, 12],

// 6
[2, 86, 68], [4, 43, 27], [4, 43, 19], [4, 43, 15],

// 7    
[2, 98, 78], [4, 49, 31], [2, 32, 14, 4, 33, 15], [4, 39, 13, 1, 40, 14],

// 8
[2, 121, 97], [2, 60, 38, 2, 61, 39], [4, 40, 18, 2, 41, 19], [4, 40, 14, 2, 41, 15],

// 9
[2, 146, 116], [3, 58, 36, 2, 59, 37], [4, 36, 16, 4, 37, 17], [4, 36, 12, 4, 37, 13],

// 10   
[2, 86, 68, 2, 87, 69], [4, 69, 43, 1, 70, 44], [6, 43, 19, 2, 44, 20], [6, 43, 15, 2, 44, 16],

// 11
[4, 101, 81], [1, 80, 50, 4, 81, 51], [4, 50, 22, 4, 51, 23], [3, 36, 12, 8, 37, 13],

// 12
[2, 116, 92, 2, 117, 93], [6, 58, 36, 2, 59, 37], [4, 46, 20, 6, 47, 21], [7, 42, 14, 4, 43, 15],

// 13
[4, 133, 107], [8, 59, 37, 1, 60, 38], [8, 44, 20, 4, 45, 21], [12, 33, 11, 4, 34, 12],

// 14
[3, 145, 115, 1, 146, 116], [4, 64, 40, 5, 65, 41], [11, 36, 16, 5, 37, 17], [11, 36, 12, 5, 37, 13],

// 15
[5, 109, 87, 1, 110, 88], [5, 65, 41, 5, 66, 42], [5, 54, 24, 7, 55, 25], [11, 36, 12],

// 16
[5, 122, 98, 1, 123, 99], [7, 73, 45, 3, 74, 46], [15, 43, 19, 2, 44, 20], [3, 45, 15, 13, 46, 16],

// 17
[1, 135, 107, 5, 136, 108], [10, 74, 46, 1, 75, 47], [1, 50, 22, 15, 51, 23], [2, 42, 14, 17, 43, 15],

// 18
[5, 150, 120, 1, 151, 121], [9, 69, 43, 4, 70, 44], [17, 50, 22, 1, 51, 23], [2, 42, 14, 19, 43, 15],

// 19
[3, 141, 113, 4, 142, 114], [3, 70, 44, 11, 71, 45], [17, 47, 21, 4, 48, 22], [9, 39, 13, 16, 40, 14],

// 20
[3, 135, 107, 5, 136, 108], [3, 67, 41, 13, 68, 42], [15, 54, 24, 5, 55, 25], [15, 43, 15, 10, 44, 16],

// 21
[4, 144, 116, 4, 145, 117], [17, 68, 42], [17, 50, 22, 6, 51, 23], [19, 46, 16, 6, 47, 17],

// 22
[2, 139, 111, 7, 140, 112], [17, 74, 46], [7, 54, 24, 16, 55, 25], [34, 37, 13],

// 23
[4, 151, 121, 5, 152, 122], [4, 75, 47, 14, 76, 48], [11, 54, 24, 14, 55, 25], [16, 45, 15, 14, 46, 16],

// 24
[6, 147, 117, 4, 148, 118], [6, 73, 45, 14, 74, 46], [11, 54, 24, 16, 55, 25], [30, 46, 16, 2, 47, 17],

// 25
[8, 132, 106, 4, 133, 107], [8, 75, 47, 13, 76, 48], [7, 54, 24, 22, 55, 25], [22, 45, 15, 13, 46, 16],

// 26
[10, 142, 114, 2, 143, 115], [19, 74, 46, 4, 75, 47], [28, 50, 22, 6, 51, 23], [33, 46, 16, 4, 47, 17],

// 27
[8, 152, 122, 4, 153, 123], [22, 73, 45, 3, 74, 46], [8, 53, 23, 26, 54, 24], [12, 45, 15, 28, 46, 16],

// 28
[3, 147, 117, 10, 148, 118], [3, 73, 45, 23, 74, 46], [4, 54, 24, 31, 55, 25], [11, 45, 15, 31, 46, 16],

// 29
[7, 146, 116, 7, 147, 117], [21, 73, 45, 7, 74, 46], [1, 53, 23, 37, 54, 24], [19, 45, 15, 26, 46, 16],

// 30
[5, 145, 115, 10, 146, 116], [19, 75, 47, 10, 76, 48], [15, 54, 24, 25, 55, 25], [23, 45, 15, 25, 46, 16],

// 31
[13, 145, 115, 3, 146, 116], [2, 74, 46, 29, 75, 47], [42, 54, 24, 1, 55, 25], [23, 45, 15, 28, 46, 16],

// 32
[17, 145, 115], [10, 74, 46, 23, 75, 47], [10, 54, 24, 35, 55, 25], [19, 45, 15, 35, 46, 16],

// 33
[17, 145, 115, 1, 146, 116], [14, 74, 46, 21, 75, 47], [29, 54, 24, 19, 55, 25], [11, 45, 15, 46, 46, 16],

// 34
[13, 145, 115, 6, 146, 116], [14, 74, 46, 23, 75, 47], [44, 54, 24, 7, 55, 25], [59, 46, 16, 1, 47, 17],

// 35
[12, 151, 121, 7, 152, 122], [12, 75, 47, 26, 76, 48], [39, 54, 24, 14, 55, 25], [22, 45, 15, 41, 46, 16],

// 36
[6, 151, 121, 14, 152, 122], [6, 75, 47, 34, 76, 48], [46, 54, 24, 10, 55, 25], [2, 45, 15, 64, 46, 16],

// 37
[17, 152, 122, 4, 153, 123], [29, 74, 46, 14, 75, 47], [49, 54, 24, 10, 55, 25], [24, 45, 15, 46, 46, 16],

// 38
[4, 152, 122, 18, 153, 123], [13, 74, 46, 32, 75, 47], [48, 54, 24, 14, 55, 25], [42, 45, 15, 32, 46, 16],

// 39
[20, 147, 117, 4, 148, 118], [40, 75, 47, 7, 76, 48], [43, 54, 24, 22, 55, 25], [10, 45, 15, 67, 46, 16],

// 40
[19, 148, 118, 6, 149, 119], [18, 75, 47, 31, 76, 48], [34, 54, 24, 34, 55, 25], [20, 45, 15, 61, 46, 16]];

QRRSBlock.getRSBlocks = function (typeNumber, errorCorrectLevel) {

  var rsBlock = QRRSBlock.getRsBlockTable(typeNumber, errorCorrectLevel);

  if (rsBlock == undefined) {
    throw new Error("bad rs block @ typeNumber:" + typeNumber + "/errorCorrectLevel:" + errorCorrectLevel);
  }

  var length = rsBlock.length / 3;

  var list = new Array();

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

    var count = rsBlock[i * 3 + 0];
    var totalCount = rsBlock[i * 3 + 1];
    var dataCount = rsBlock[i * 3 + 2];

    for (var j = 0; j < count; j++) {
      list.push(new QRRSBlock(totalCount, dataCount));
    }
  }

  return list;
};

QRRSBlock.getRsBlockTable = function (typeNumber, errorCorrectLevel) {

  switch (errorCorrectLevel) {
    case QRErrorCorrectLevel.L:
      return QRRSBlock.RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 0];
    case QRErrorCorrectLevel.M:
      return QRRSBlock.RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 1];
    case QRErrorCorrectLevel.Q:
      return QRRSBlock.RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 2];
    case QRErrorCorrectLevel.H:
      return QRRSBlock.RS_BLOCK_TABLE[(typeNumber - 1) * 4 + 3];
    default:
      return undefined;
  }
};

//---------------------------------------------------------------------
// QRBitBuffer
//---------------------------------------------------------------------

function QRBitBuffer() {
  this.buffer = new Array();
  this.length = 0;
}

QRBitBuffer.prototype = {

  get: function (index) {
    var bufIndex = Math.floor(index / 8);
    return (this.buffer[bufIndex] >>> 7 - index % 8 & 1) == 1;
  },

  put: function (num, length) {
    for (var i = 0; i < length; i++) {
      this.putBit((num >>> length - i - 1 & 1) == 1);
    }
  },

  getLengthInBits: function () {
    return this.length;
  },

  putBit: function (bit) {

    var bufIndex = Math.floor(this.length / 8);
    if (this.buffer.length <= bufIndex) {
      this.buffer.push(0);
    }

    if (bit) {
      this.buffer[bufIndex] |= 0x80 >>> this.length % 8;
    }

    this.length++;
  }
};

// support Chinese
function utf16to8(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;
}

function drawQrcode(options) {
  options = options || {};
  options = extend(true, {
    width: 256,
    height: 256,
    x: 0,
    y: 0,
    typeNumber: -1,
    correctLevel: QRErrorCorrectLevel.H,
    background: '#ffffff',
    foreground: '#000000',
    image: {
      imageResource: '',
      dx: 0,
      dy: 0,
      dWidth: 100,
      dHeight: 100
    }
  }, options);

  if (!options.ctx) {
    console.warn('please set ctx!');
    return;
  }

  createCanvas();
  function createCanvas() {
    // create the qrcode itself
    var qrcode = new QRCode(options.typeNumber, options.correctLevel);
    qrcode.addData(utf16to8(options.text));
    qrcode.make();

    // get canvas context
    var ctx= options.ctx;
    // compute tileW/tileH based on options.width/options.height
    var tileW = options.width / qrcode.getModuleCount();
    var tileH = options.height / qrcode.getModuleCount();
    // draw in the canvas
    for (var row = 0; row < qrcode.getModuleCount(); row++) {
      for (var col = 0; col < qrcode.getModuleCount(); col++) {
        var style = qrcode.isDark(row, col) ? options.foreground : options.background;
        ctx.fillStyle=style;
        var w = Math.ceil((col + 1) * tileW) - Math.floor(col * tileW);
        var h = Math.ceil((row + 1) * tileW) - Math.floor(row * tileW);
        ctx.fillRect(Math.round(col * tileW) + options.x, Math.round(row * tileH) + options.y, w, h);
      }
    }
    if (options.image.imageResource) {
      ctx.drawImage(options.image.imageResource, options.image.dx, options.image.dy, options.image.dWidth, options.image.dHeight);
    }
  }
}
return drawQrcode;
})));

2.wxml页面

  <canvas type="2d" id="qrcode" style="width: 100%;height: 100%;"></canvas>

3.js页面

//这里导入是小编的地址，根据自己创建的地址对应导入
import drawQrcode from '../../../utils/qrcode/weapp.qrcode.esm'

data: {
    // 二维码路径
    ewm_image:"",
    // 生成二维码的图片路径
    qrImg:""
  },

// 生成二维码
  getcode() {
    let that = this
    const query = wx.createSelectorQuery()
    query.select('#qrcode')
      .fields({ node: true, size: true })
      .exec((res) => {
        const canvas = res[0].node
        const ctx = canvas.getContext('2d')
        // let dpr=1
        canvas.width = 300
        canvas.height = 300
          // 调用方法drawQrcode生成二维码
          drawQrcode({
            ctx: ctx,
            width:300,
            height:300,
            text: that.data.ewm_image,        //这个that.data.ewm_image是后端传过来的地址，必须先获取
          })
          // 获取临时路径（得到之后，想干嘛就干嘛了）
        wx.canvasToTempFilePath({
          canvasId: 'qrcode',
          canvas: canvas,
          x: 0,
          y: 0,
          width: 260,
          height: 260,
          padding:30,
          // 同比例放大，决定了保存图片的清晰程度
          destWidth: 260*2.5,
          destHeight: 260*2.5,
          // 图片质量
          quality: 1,
          success(res) { 
            that.setData({
              'qrImg':res.tempFilePath            //qrImg是canvas画布生成图片存储
            })
          },
          fail(err){
            console.log("err",err)
          }
        })
      })
  },

注：切记，必须先获取后端传过来的二维码地址，再画图