首先在utils文件下创建barcode.js与index.js两个文件
1.在barcode.js中复制如下代码（此代码已经改动过，测试可用）：
var CHAR_TILDE = 126;
var CODE_FNC1 = 102;
var SET_STARTA = 103;
var SET_STARTB = 104;
var SET_STARTC = 105;
var SET_SHIFT = 98;
var SET_CODEA = 101;
var SET_CODEB = 100;
var SET_STOP = 106;
var REPLACE_CODES = {
CHAR_TILDE: CODE_FNC1 //~ corresponds to FNC1 in GS1-128 standard
}
var CODESET = {
ANY: 1,
AB: 2,
A: 3,
B: 4,
C: 5
};
function getBytes(str) {
var bytes = [];
for (var i = 0; i < str.length; i++) {
bytes.push(str.charCodeAt(i));
}
return bytes;
}
exports.code128 = function (ctx, text, width, height) {
width = parseInt(width);
height = parseInt(height);
var codes = stringToCode128(text);
var g = new Graphics(ctx, width, height);
var barWeight = g.area.width / ((codes.length - 3) * 11 + 35);
var x = g.area.left;
var y = g.area.top;
for (var i = 0; i < codes.length; i++) {
var c = codes[i];
//two bars at a time: 1 black and 1 white
for (var bar = 0; bar < 8; bar += 2) {
var barW = PATTERNS[c][bar] * barWeight;
// var barH = height - y - this.border;
var barH = height - y;
var spcW = PATTERNS[c][bar + 1] * barWeight;
//no need to draw if 0 width
if (barW > 0) {
g.fillFgRect(x, y, barW, barH);
}
x += barW + spcW;
}
}
ctx.draw();
}
function stringToCode128(text) {
var barc = {
currcs: CODESET.C
};
var bytes = getBytes(text);
//decide starting codeset
var index = bytes[0] == CHAR_TILDE ? 1 : 0;
var csa1 = bytes.length > 0 ? codeSetAllowedFor(bytes[index++]) : CODESET.AB;
var csa2 = bytes.length > 0 ? codeSetAllowedFor(bytes[index++]) : CODESET.AB;
barc.currcs = getBestStartSet(csa1, csa2);
barc.currcs = perhapsCodeC(bytes, barc.currcs);
//if no codeset changes this will end up with bytes.length+3
//start, checksum and stop
var codes = new Array();
switch (barc.currcs) {
case CODESET.A:
codes.push(SET_STARTA);
break;
case CODESET.B:
codes.push(SET_STARTB);
break;
default:
codes.push(SET_STARTC);
break;
}
for (var i = 0; i < bytes.length; i++) {
var b1 = bytes[i]; //get the first of a pair
//should we translate/replace
if (b1 in REPLACE_CODES) {
codes.push(REPLACE_CODES[b1]);
i++ //jump to next
b1 = bytes[i];
}
//get the next in the pair if possible
var b2 = bytes.length > (i + 1) ? bytes[i + 1] : -1;
codes = codes.concat(codesForChar(b1, b2, barc.currcs));
//code C takes 2 chars each time
if (barc.currcs == CODESET.C) i++;
}
//calculate checksum according to Code 128 standards
var checksum = codes[0];
for (var weight = 1; weight < codes.length; weight++) {
checksum += (weight * codes[weight]);
}
codes.push(checksum % 103);
codes.push(SET_STOP);
//encoding should now be complete
return codes;
function getBestStartSet(csa1, csa2) {
//tries to figure out the best codeset
//to start with to get the most compact code
var vote = 0;
vote += csa1 == CODESET.A ? 1 : 0;
vote += csa1 == CODESET.B ? -1 : 0;
vote += csa2 == CODESET.A ? 1 : 0;
vote += csa2 == CODESET.B ? -1 : 0;
//tie goes to B due to my own predudices
return vote > 0 ? CODESET.A : CODESET.B;
}
function perhapsCodeC(bytes, codeset) {
for (var i = 0; i < bytes.length; i++) {
var b = bytes[i]
if ((b < 48 || b > 57) && b != CHAR_TILDE)
return codeset;
}
if (bytes.length % 2 == 0) {
return CODESET.C
}else{
return CODESET.A;
}
}
//chr1 is current byte
//chr2 is the next byte to process. looks ahead.
function codesForChar(chr1, chr2, currcs) {
var result = [];
var shifter = -1;
if (charCompatible(chr1, currcs)) {
if (currcs == CODESET.C) {
if (chr2 == -1) {
shifter = SET_CODEB;
currcs = CODESET.B;
}
else if ((chr2 != -1) && !charCompatible(chr2, currcs)) {
//need to check ahead as well
if (charCompatible(chr2, CODESET.A)) {
shifter = SET_CODEA;
currcs = CODESET.A;
}
else {
shifter = SET_CODEB;
currcs = CODESET.B;
}
}
}
}
else {
//if there is a next char AND that next char is also not compatible
if ((chr2 != -1) && !charCompatible(chr2, currcs)) {
//need to switch code sets
switch (currcs) {
case CODESET.A:
shifter = SET_CODEB;
currcs = CODESET.B;
break;
case CODESET.B:
shifter = SET_CODEA;
currcs = CODESET.A;
break;
}
}
else {
//no need to shift code sets, a temporary SHIFT will suffice
shifter = SET_SHIFT;
}
}
//ok some type of shift is nessecary
if (shifter != -1) {
result.push(shifter);
result.push(codeValue(chr1));
}
else {
if (currcs == CODESET.C) {
//include next as well
result.push(codeValue(chr1, chr2));
}
else {
result.push(codeValue(chr1));
}
}
barc.currcs = currcs;
return result;
}
}
//reduce the ascii code to fit into the Code128 char table
function codeValue(chr1, chr2) {
if (typeof chr2 == "undefined") {
return chr1 >= 32 ? chr1 - 32 : chr1 + 64;
}
else {
return parseInt(String.fromCharCode(chr1) + String.fromCharCode(chr2));
}
}
function charCompatible(chr, codeset) {
var csa = codeSetAllowedFor(chr);
if (csa == CODESET.ANY) return true;
//if we need to change from current
if (csa == CODESET.AB) return true;
if (csa == CODESET.A && codeset == CODESET.A) return true;
if (csa == CODESET.B && codeset == CODESET.B) return true;
return false;
}
function codeSetAllowedFor(chr) {
if (chr >= 48 && chr <= 57) {
//0-9
return CODESET.ANY;
}
else if (chr >= 32 && chr <= 95) {
//0-9 A-Z
return CODESET.AB;
}
else {
//if non printable
return chr < 32 ? CODESET.A : CODESET.B;
}
}
var Graphics = function (ctx, width, height) {
this.width = width;
this.height = height;
this.quiet = Math.round(this.width / 40);
this.border_size = 0;
this.padding_width = 0;
this.area = {
width: width - this.padding_width * 2 - this.quiet * 2,
height: height - this.border_size * 2,
top: this.border_size - 4,
left: this.padding_width + this.quiet
};
this.ctx = ctx;
this.fg = "#000000";
this.bg = "#ffffff";
// fill background
this.fillBgRect(0, 0, width, height);
// fill center to create border
this.fillBgRect(0, this.border_size, width, height - this.border_size * 2);
}
//use native color
Graphics.prototype._fillRect = function (x, y, width, height, color) {
this.ctx.setFillStyle(color)
this.ctx.fillRect(x, y, width, height)
}
Graphics.prototype.fillFgRect = function (x, y, width, height) {
this._fillRect(x, y, width, height, this.fg);
}
Graphics.prototype.fillBgRect = function (x, y, width, height) {
this._fillRect(x, y, width, height, this.bg);
}
var PATTERNS = [
[2, 1, 2, 2, 2, 2, 0, 0], // 0
[2, 2, 2, 1, 2, 2, 0, 0], // 1
[2, 2, 2, 2, 2, 1, 0, 0], // 2
[1, 2, 1, 2, 2, 3, 0, 0], // 3
[1, 2, 1, 3, 2, 2, 0, 0], // 4
[1, 3, 1, 2, 2, 2, 0, 0], // 5
[1, 2, 2, 2, 1, 3, 0, 0], // 6
[1, 2, 2, 3, 1, 2, 0, 0], // 7
[1, 3, 2, 2, 1, 2, 0, 0], // 8
[2, 2, 1, 2, 1, 3, 0, 0], // 9
[2, 2, 1, 3, 1, 2, 0, 0], // 10
[2, 3, 1, 2, 1, 2, 0, 0], // 11
[1, 1, 2, 2, 3, 2, 0, 0], // 12
[1, 2, 2, 1, 3, 2, 0, 0], // 13
[1, 2, 2, 2, 3, 1, 0, 0], // 14
[1, 1, 3, 2, 2, 2, 0, 0], // 15
[1, 2, 3, 1, 2, 2, 0, 0], // 16
[1, 2, 3, 2, 2, 1, 0, 0], // 17
[2, 2, 3, 2, 1, 1, 0, 0], // 18
[2, 2, 1, 1, 3, 2, 0, 0], // 19
[2, 2, 1, 2, 3, 1, 0, 0], // 20
[2, 1, 3, 2, 1, 2, 0, 0], // 21
[2, 2, 3, 1, 1, 2, 0, 0], // 22
[3, 1, 2, 1, 3, 1, 0, 0], // 23
[3, 1, 1, 2, 2, 2, 0, 0], // 24
[3, 2, 1, 1, 2, 2, 0, 0], // 25
[3, 2, 1, 2, 2, 1, 0, 0], // 26
[3, 1, 2, 2, 1, 2, 0, 0], // 27
[3, 2, 2, 1, 1, 2, 0, 0], // 28
[3, 2, 2, 2, 1, 1, 0, 0], // 29
[2, 1, 2, 1, 2, 3, 0, 0], // 30
[2, 1, 2, 3, 2, 1, 0, 0], // 31
[2, 3, 2, 1, 2, 1, 0, 0], // 32
[1, 1, 1, 3, 2, 3, 0, 0], // 33
[1, 3, 1, 1, 2, 3, 0, 0], // 34
[1, 3, 1, 3, 2, 1, 0, 0], // 35
[1, 1, 2, 3, 1, 3, 0, 0], // 36
[1, 3, 2, 1, 1, 3, 0, 0], // 37
[1, 3, 2, 3, 1, 1, 0, 0], // 38
[2, 1, 1, 3, 1, 3, 0, 0], // 39
[2, 3, 1, 1, 1, 3, 0, 0], // 40
[2, 3, 1, 3, 1, 1, 0, 0], // 41
[1, 1, 2, 1, 3, 3, 0, 0], // 42
[1, 1, 2, 3, 3, 1, 0, 0], // 43
[1, 3, 2, 1, 3, 1, 0, 0], // 44
[1, 1, 3, 1, 2, 3, 0, 0], // 45
[1, 1, 3, 3, 2, 1, 0, 0], // 46
[1, 3, 3, 1, 2, 1, 0, 0], // 47
[3, 1, 3, 1, 2, 1, 0, 0], // 48
[2, 1, 1, 3, 3, 1, 0, 0], // 49
[2, 3, 1, 1, 3, 1, 0, 0], // 50
[2, 1, 3, 1, 1, 3, 0, 0], // 51
[2, 1, 3, 3, 1, 1, 0, 0], // 52
[2, 1, 3, 1, 3, 1, 0, 0], // 53
[3, 1, 1, 1, 2, 3, 0, 0], // 54
[3, 1, 1, 3, 2, 1, 0, 0], // 55
[3, 3, 1, 1, 2, 1, 0, 0], // 56
[3, 1, 2, 1, 1, 3, 0, 0], // 57
[3, 1, 2, 3, 1, 1, 0, 0], // 58
[3, 3, 2, 1, 1, 1, 0, 0], // 59
[3, 1, 4, 1, 1, 1, 0, 0], // 60
[2, 2, 1, 4, 1, 1, 0, 0], // 61
[4, 3, 1, 1, 1, 1, 0, 0], // 62
[1, 1, 1, 2, 2, 4, 0, 0], // 63
[1, 1, 1, 4, 2, 2, 0, 0], // 64
[1, 2, 1, 1, 2, 4, 0, 0], // 65
[1, 2, 1, 4, 2, 1, 0, 0], // 66
[1, 4, 1, 1, 2, 2, 0, 0], // 67
[1, 4, 1, 2, 2, 1, 0, 0], // 68
[1, 1, 2, 2, 1, 4, 0, 0], // 69
[1, 1, 2, 4, 1, 2, 0, 0], // 70
[1, 2, 2, 1, 1, 4, 0, 0], // 71
[1, 2, 2, 4, 1, 1, 0, 0], // 72
[1, 4, 2, 1, 1, 2, 0, 0], // 73
[1, 4, 2, 2, 1, 1, 0, 0], // 74
[2, 4, 1, 2, 1, 1, 0, 0], // 75
[2, 2, 1, 1, 1, 4, 0, 0], // 76
[4, 1, 3, 1, 1, 1, 0, 0], // 77
[2, 4, 1, 1, 1, 2, 0, 0], // 78
[1, 3, 4, 1, 1, 1, 0, 0], // 79
[1, 1, 1, 2, 4, 2, 0, 0], // 80
[1, 2, 1, 1, 4, 2, 0, 0], // 81
[1, 2, 1, 2, 4, 1, 0, 0], // 82
[1, 1, 4, 2, 1, 2, 0, 0], // 83
[1, 2, 4, 1, 1, 2, 0, 0], // 84
[1, 2, 4, 2, 1, 1, 0, 0], // 85
[4, 1, 1, 2, 1, 2, 0, 0], // 86
[4, 2, 1, 1, 1, 2, 0, 0], // 87
[4, 2, 1, 2, 1, 1, 0, 0], // 88
[2, 1, 2, 1, 4, 1, 0, 0], // 89
[2, 1, 4, 1, 2, 1, 0, 0], // 90
[4, 1, 2, 1, 2, 1, 0, 0], // 91
[1, 1, 1, 1, 4, 3, 0, 0], // 92
[1, 1, 1, 3, 4, 1, 0, 0], // 93
[1, 3, 1, 1, 4, 1, 0, 0], // 94
[1, 1, 4, 1, 1, 3, 0, 0], // 95
[1, 1, 4, 3, 1, 1, 0, 0], // 96
[4, 1, 1, 1, 1, 3, 0, 0], // 97
[4, 1, 1, 3, 1, 1, 0, 0], // 98
[1, 1, 3, 1, 4, 1, 0, 0], // 99
[1, 1, 4, 1, 3, 1, 0, 0], // 100
[3, 1, 1, 1, 4, 1, 0, 0], // 101
[4, 1, 1, 1, 3, 1, 0, 0], // 102
[2, 1, 1, 4, 1, 2, 0, 0], // 103
[2, 1, 1, 2, 1, 4, 0, 0], // 104
[2, 1, 1, 2, 3, 2, 0, 0], // 105
[2, 3, 3, 1, 1, 1, 2, 0] // 106
]
2.index.js中复制以下代码：
var barcode = require('./barcode');
function convert_length(length) {
return Math.round(wx.getSystemInfoSync().windowWidth * length / 750);
}
function barc(id, code, width, height) {
barcode.code128(wx.createCanvasContext(id), code, convert_length(width), convert_length(height))
}
module.exports = {
barcode: barc
}
3.wxml中添加代码：
4.js中添加代码：
注意在设置条码的宽的时候一定要刚好合适，不然会不能扫描或者不容易扫描，调动宽度的时候要根据code的位数来调整。
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