在微信小程序如何wx.chooseImage的图片路径转成Base64

最新推荐文章于 2025-07-02 19:02:06 发布

原创最新推荐文章于 2025-07-02 19:02:06 发布 · 9.5k 阅读

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#微信 #base64 #javascript

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本文介绍了一个使用JavaScript实现的Base64编码和解码的算法，该算法能够处理不同长度的Unicode字符，并提供了从UTF-8到Base64及反向转换的方法。

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js文件：

(function(){
var BASE64_MAPPING=[
'A','B','C','D','E','F','G','H',
'I','J','K','L','M','N','O','P',
'Q','R','S','T','U','V','W','X',
'Y','Z','a','b','c','d','e','f',
'g','h','i','j','k','l','m','n',
'o','p','q','r','s','t','u','v',
'w','x','y','z','0','1','2','3',
'4','5','6','7','8','9','+','/'
];

/**
*ascii convert to binary
*/
var _toBinary=function(ascii){
var binary=new
 Array();
while(ascii>0){
var b= ascii%2;
ascii = Math.floor(ascii/2);
binary.push(b);
}
/*
var len = binary.length;
if(6-len > 0){
for(var i = 6-len ; i > 0 ; --i){
binary.push(0);
}
}*/
binary.reverse();
return binary;
};

/**
*binary convert to decimal
*/
var _toDecimal=function(binary){
var dec=0;
var p=0;
for(var i= binary.length-1;
 i >= 
0;--i){
var b= binary[i];
if(b==1){
dec += Math.pow(2,
 p);
}
++p;
}
return dec;
};

/**
*unicode convert to utf-8
*/
var _toUTF8Binary=function(c,
 binaryArray){
var mustLen=(8-(c+1))+((c-1)*6);
var fatLen= binaryArray.length;
var diff= mustLen-
 fatLen;
while(--diff>=0){
binaryArray.unshift(0);
}
var binary=[];
var _c= c;
while(--_c>=0){
binary.push(1);
}
binary.push(0);
var i=0,
 len= 
8-(c+1);
for(; i< len;
++i){
binary.push(binaryArray[i]);
}

for(var j=0;
 j< c-1;++j){
binary.push(1);
binary.push(0);
var sum=6;
while(--sum>=0){
binary.push(binaryArray[i++]);
}
}
return binary;
};

var __BASE64={
/**
*BASE64 Encode
*/
encoder:function(str){
var base64_Index=[];
var binaryArray=[];
for(var i=0,
 len= str.length; i<
 len ;++i){
var unicode= str.charCodeAt(i);
var _tmpBinary= _toBinary(unicode);
if(unicode<0x80){
var _tmpdiff=8-
 _tmpBinary.length;
while(--_tmpdiff>=0){
_tmpBinary.unshift(0);
}
binaryArray = binaryArray.concat(_tmpBinary);
}elseif(unicode>=0x80&&
 unicode<= 
0x7FF){
binaryArray = binaryArray.concat(_toUTF8Binary(2,
 _tmpBinary));
}elseif(unicode>=0x800&&
 unicode<= 
0xFFFF){//UTF-8 3byte
binaryArray = binaryArray.concat(_toUTF8Binary(3,
 _tmpBinary));
}elseif(unicode>=0x10000&&
 unicode<= 
0x1FFFFF){//UTF-8 4byte
binaryArray = binaryArray.concat(_toUTF8Binary(4,
 _tmpBinary));
}elseif(unicode>=0x200000&&
 unicode<= 
0x3FFFFFF){//UTF-8 5byte
binaryArray = binaryArray.concat(_toUTF8Binary(5,
 _tmpBinary));
}elseif(unicode>=4000000&&
 unicode<= 
0x7FFFFFFF){//UTF-8 6byte
binaryArray = binaryArray.concat(_toUTF8Binary(6,
 _tmpBinary));
}
}

var extra_Zero_Count=0;
for(var i=0,
 len= binaryArray.length; i<
 len ; i+=6){
var diff=(i+6)-len;
if(diff==2){
extra_Zero_Count =2;
}elseif(diff==4){
extra_Zero_Count =4;
}
//if(extra_Zero_Count > 0){
// len += extra_Zero_Count+1;
//}
var _tmpExtra_Zero_Count= extra_Zero_Count;
while(--_tmpExtra_Zero_Count>=0){
binaryArray.push(0);
}
base64_Index.push(_toDecimal(binaryArray.slice(i,
 i+6)));
}

var base64='';
for(var i=0,
 len= base64_Index.length; i<
 len ;++i){
base64 += BASE64_MAPPING[base64_Index[i]];
}

for(var i=0,
 len= extra_Zero_Count/2;
 i < len 
;++i){
base64 +='=';
}
return base64;
},
/**
*BASE64 Decode for UTF-8
*/
decoder :function(_base64Str){
var _len= _base64Str.length;
var extra_Zero_Count=0;
/**
* 计算在进行Base64编码的时候补了几个0
*/
if(_base64Str.charAt(_len-1)=='='){
//alert(_base64Str.charAt(_len-1));
//alert(_base64Str.charAt(_len-2));
if(_base64Str.charAt(_len-2)=='='){//两个等号说明补了4个0
extra_Zero_Count =4;
_base64Str = _base64Str.substring(0,
 _len-2);
}else{//一个等号说明补了2个0
extra_Zero_Count =2;
_base64Str = _base64Str.substring(0,
 _len - 
1);
}
}

var binaryArray=[];
for(var i=0,
 len= _base64Str.length; i<
 len ; 
++i){
var c= _base64Str.charAt(i);
for(var j=0,
 size= BASE64_MAPPING.length; j<
 size ;++j){
if(c== BASE64_MAPPING[j]){
var _tmp= _toBinary(j);
//不足六位的补0
var _tmpLen= _tmp.length;
if(6-_tmpLen>0){
for(var k=6-_tmpLen;
 k> 
0;--k){
_tmp.unshift(0);
}
}
binaryArray = binaryArray.concat(_tmp);
break;
}
}
}

if(extra_Zero_Count>0){
binaryArray = binaryArray.slice(0,
 binaryArray.length- extra_Zero_Count);
}

var unicode=[];
var unicodeBinary=[];
for(var i=0,
 len= binaryArray.length; i<
 len ;){
if(binaryArray[i]==0){
unicode=unicode.concat(_toDecimal(binaryArray.slice(i,i+8)));
i +=8;
}else{
var sum=0;
while(i< len){
if(binaryArray[i]==1){
++sum;
}else{
break;
}
++i;
}
unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+1,
 i+8-sum));
i +=8- sum;
while(sum>1){
unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+2,
 i+8));
i +=8;
--sum;
}
unicode = unicode.concat(_toDecimal(unicodeBinary));
unicodeBinary =[];
}
}
return unicode;
}
};

//window.BASE64 = __BASE64;
module.exports={
CusBASE64: __BASE64
}
})();

程序引入：

var Base64 
= require("../../../utils/base64.js");

转成Base64:

wx.chooseImage(
{
success:function(res){
var path= res.tempFilePaths[0];
var Path= Base64.CusBASE64.encoder(path);
Meths.Console("本地图片路径base6458：",
 Path);
})