由于小程序无法使用dom操作,window、document都是undefined。常用恩qrcode组件不可使用。
我在项目中使用qr-image这个模块,npm中下载即可。 代码具体如下:
var qr = require('qr-image')
var code = qr.imageSync(this.data.url, { type: 'png' })
let base64Url = this._arrayBufferToBase64(code)
上述base64Url就是生成base64的图片数据。 _arrayBufferToBase64是将Uint8Array转成base64的方法。两部即可实现展示二维码。
_arrayBufferToBase64(raw) {
var base64 = '';
var encodings = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
var bytes = new Uint8Array(raw);
var byteLength = bytes.byteLength;
var byteRemainder = byteLength % 3;
var mainLength = byteLength - byteRemainder;
var a, b, c, d;
var chunk;
// Main loop deals with bytes in chunks of 3
for (var i = 0; i < mainLength; i = i + 3) {
// Combine the three bytes into a single integer
chunk = (bytes[i] << 16) | (bytes[i + 1] << 8) | bytes[i + 2];
// Use bitmasks to extract 6-bit segments from the triplet
a = (chunk & 16515072) >> 18; // 16515072 = (2^6 - 1) << 18
b = (chunk & 258048) >> 12; // 258048 = (2^6 - 1) << 12
c = (chunk & 4032) >> 6; // 4032 = (2^6 - 1) << 6
d = chunk & 63; // 63 = 2^6 - 1
// Convert the raw binary segments to the appropriate ASCII encoding
base64 += encodings[a] + encodings[b] + encodings[c] + encodings[d];
}
// Deal with the remaining bytes and padding
if (byteRemainder == 1) {
chunk = bytes[mainLength];
a = (chunk & 252) >> 2 // 252 = (2^6 - 1) << 2;
// Set the 4 least significant bits to zero
b = (chunk & 3) << 4 // 3 = 2^2 - 1;
base64 += encodings[a] + encodings[b] + '==';
}
else if (byteRemainder == 2) {
chunk = (bytes[mainLength] << 8) | bytes[mainLength + 1];
a = (chunk & 16128) >> 8 // 16128 = (2^6 - 1) << 8;
b = (chunk & 1008) >> 4 // 1008 = (2^6 - 1) << 4;
// Set the 2 least significant bits to zero
c = (chunk & 15) << 2 // 15 = 2^4 - 1;
base64 += encodings[a] + encodings[b] + encodings[c] + '=';
}
return "data:image/jpeg;base64," + base64;
},