我有一个PHP脚本,可以将PNG图像编码为Base64字符串。

我想用JavaScript做同样的事情。我知道如何打开文件,但我不知道如何进行编码。我不习惯使用二进制数据。


当前回答

JavaScript没有btoa中间步骤(没有库)

在问题标题中你写的是字符串转换,但在问题中你谈论的是二进制数据(图片),所以这里有一个函数,从PNG图片二进制数据开始进行适当的转换(详细信息和反转转换在这里)。

function bytesArrToBase64(arr) { const abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; // base64 alphabet const bin = n => n.toString(2).padStart(8,0); // convert num to 8-bit binary string const l = arr.length let result = ''; for(let i=0; i<=(l-1)/3; i++) { let c1 = i*3+1>=l; // case when "=" is on end let c2 = i*3+2>=l; // case when "=" is on end let chunk = bin(arr[3*i]) + bin(c1? 0:arr[3*i+1]) + bin(c2? 0:arr[3*i+2]); let r = chunk.match(/.{1,6}/g).map((x,j)=> j==3&&c2 ? '=' :(j==2&&c1 ? '=':abc[+('0b'+x)])); result += r.join(''); } return result; } // TEST const pic = [ // PNG binary data 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x10, 0x08, 0x06, 0x00, 0x00, 0x00, 0x1f, 0xf3, 0xff, 0x61, 0x00, 0x00, 0x00, 0x01, 0x73, 0x52, 0x47, 0x42, 0x00, 0xae, 0xce, 0x1c, 0xe9, 0x00, 0x00, 0x01, 0x59, 0x69, 0x54, 0x58, 0x74, 0x58, 0x4d, 0x4c, 0x3a, 0x63, 0x6f, 0x6d, 0x2e, 0x61, 0x64, 0x6f, 0x62, 0x65, 0x2e, 0x78, 0x6d, 0x70, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c, 0x78, 0x3a, 0x78, 0x6d, 0x70, 0x6d, 0x65, 0x74, 0x61, 0x20, 0x78, 0x6d, 0x6c, 0x6e, 0x73, 0x3a, 0x78, 0x3d, 0x22, 0x61, 0x64, 0x6f, 0x62, 0x65, 0x3a, 0x6e, 0x73, 0x3a, 0x6d, 0x65, 0x74, 0x61, 0x2f, 0x22, 0x20, 0x78, 0x3a, 0x78, 0x6d, 0x70, 0x74, 0x6b, 0x3d, 0x22, 0x58, 0x4d, 0x50, 0x20, 0x43, 0x6f, 0x72, 0x65, 0x20, 0x35, 0x2e, 0x34, 0x2e, 0x30, 0x22, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x3c, 0x72, 0x64, 0x66, 0x3a, 0x52, 0x44, 0x46, 0x20, 0x78, 0x6d, 0x6c, 0x6e, 0x73, 0x3a, 0x72, 0x64, 0x66, 0x3d, 0x22, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x77, 0x77, 0x77, 0x2e, 0x77, 0x33, 0x2e, 0x6f, 0x72, 0x67, 0x2f, 0x31, 0x39, 0x39, 0x39, 0x2f, 0x30, 0x32, 0x2f, 0x32, 0x32, 0x2d, 0x72, 0x64, 0x66, 0x2d, 0x73, 0x79, 0x6e, 0x74, 0x61, 0x78, 0x2d, 0x6e, 0x73, 0x23, 0x22, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x3c, 0x72, 0x64, 0x66, 0x3a, 0x44, 0x65, 0x73, 0x63, 0x72, 0x69, 0x70, 0x74, 0x69, 0x6f, 0x6e, 0x20, 0x72, 0x64, 0x66, 0x3a, 0x61, 0x62, 0x6f, 0x75, 0x74, 0x3d, 0x22, 0x22, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x78, 0x6d, 0x6c, 0x6e, 0x73, 0x3a, 0x74, 0x69, 0x66, 0x66, 0x3d, 0x22, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x6e, 0x73, 0x2e, 0x61, 0x64, 0x6f, 0x62, 0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x74, 0x69, 0x66, 0x66, 0x2f, 0x31, 0x2e, 0x30, 0x2f, 0x22, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x3c, 0x74, 0x69, 0x66, 0x66, 0x3a, 0x4f, 0x72, 0x69, 0x65, 0x6e, 0x74, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3e, 0x31, 0x3c, 0x2f, 0x74, 0x69, 0x66, 0x66, 0x3a, 0x4f, 0x72, 0x69, 0x65, 0x6e, 0x74, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x3c, 0x2f, 0x72, 0x64, 0x66, 0x3a, 0x44, 0x65, 0x73, 0x63, 0x72, 0x69, 0x70, 0x74, 0x69, 0x6f, 0x6e, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x3c, 0x2f, 0x72, 0x64, 0x66, 0x3a, 0x52, 0x44, 0x46, 0x3e, 0x0a, 0x3c, 0x2f, 0x78, 0x3a, 0x78, 0x6d, 0x70, 0x6d, 0x65, 0x74, 0x61, 0x3e, 0x0a, 0x4c, 0xc2, 0x27, 0x59, 0x00, 0x00, 0x00, 0xf9, 0x49, 0x44, 0x41, 0x54, 0x38, 0x11, 0x95, 0x93, 0x3d, 0x0a, 0x02, 0x41, 0x0c, 0x85, 0xb3, 0xb2, 0x85, 0xb7, 0x10, 0x6c, 0x04, 0x1b, 0x0b, 0x4b, 0x6f, 0xe2, 0x76, 0x1e, 0xc1, 0xc2, 0x56, 0x6c, 0x2d, 0xbc, 0x85, 0xde, 0xc4, 0xd2, 0x56, 0xb0, 0x11, 0xbc, 0x85, 0x85, 0xa0, 0xfb, 0x46, 0xbf, 0xd9, 0x30, 0x33, 0x88, 0x06, 0x76, 0x93, 0x79, 0x93, 0xf7, 0x92, 0xf9, 0xab, 0xcc, 0xec, 0xd9, 0x7e, 0x7f, 0xd9, 0x63, 0x33, 0x8e, 0xf9, 0x75, 0x8c, 0x92, 0xe0, 0x34, 0xe8, 0x27, 0x88, 0xd9, 0xf4, 0x76, 0xcf, 0xb0, 0xaa, 0x45, 0xb2, 0x0e, 0x4a, 0xe4, 0x94, 0x39, 0x59, 0x0c, 0x03, 0x54, 0x14, 0x58, 0xce, 0xbb, 0xea, 0xdb, 0xd1, 0x3b, 0x71, 0x75, 0xb9, 0x9a, 0xe2, 0x7a, 0x7d, 0x36, 0x3f, 0xdf, 0x4b, 0x95, 0x35, 0x09, 0x09, 0xef, 0x73, 0xfc, 0xfa, 0x85, 0x67, 0x02, 0x3e, 0x59, 0x55, 0x31, 0x89, 0x31, 0x56, 0x8c, 0x78, 0xb6, 0x04, 0xda, 0x23, 0x01, 0x01, 0xc8, 0x8c, 0xe5, 0x77, 0x87, 0xbb, 0x65, 0x02, 0x24, 0xa4, 0xad, 0x82, 0xcb, 0x4b, 0x4c, 0x64, 0x59, 0x14, 0xa0, 0x72, 0x40, 0x3f, 0xbf, 0xe6, 0x68, 0xb6, 0x9f, 0x75, 0x08, 0x63, 0xc8, 0x9a, 0x09, 0x02, 0x25, 0x32, 0x34, 0x48, 0x7e, 0xcc, 0x7d, 0x10, 0xaf, 0xa6, 0xd5, 0xd2, 0x1a, 0x3d, 0x89, 0x38, 0xf5, 0xf1, 0x14, 0xb4, 0x69, 0x6a, 0x4d, 0x15, 0xf5, 0xc9, 0xf0, 0x5c, 0x1a, 0x61, 0x8a, 0x75, 0xd1, 0xe8, 0x3a, 0x2c, 0x41, 0x5d, 0x70, 0x41, 0x20, 0x29, 0xf9, 0x9b, 0xb1, 0x37, 0xc5, 0x4d, 0xfc, 0x45, 0x84, 0x7d, 0x08, 0x8f, 0x89, 0x76, 0x54, 0xf1, 0x1b, 0x19, 0x92, 0xef, 0x2c, 0xbe, 0x46, 0x8e, 0xa6, 0x49, 0x5e, 0x61, 0x89, 0xe4, 0x05, 0x5e, 0x4e, 0xa4, 0x5c, 0x10, 0x6e, 0x9f, 0xfc, 0x5b, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82 ]; let b64pic = bytesArrToBase64(pic); myPic.src = "data:image/png;base64,"+b64pic; msg.innerHTML = "Base64 encoded pic data:<br>" + b64pic; img { zoom: 10; image-rendering: pixelated; } #msg { word-break: break-all; } <img id="myPic"> <code id="msg"></code>

其他回答

你可以用window。Btoa和window.atob…

const encoded = window.btoa('Alireza Dezfoolian'); // encode a string
const decoded = window.atob(encoded); // decode the string

也许使用MDN的方式可以最好地完成你的工作…也接受Unicode…使用这两个简单的函数:

// UCS-2 string to Base64 encoded ASCII
function utoa(str) {
    return window.btoa(unescape(encodeURIComponent(str)));
}
// Base64 encoded ASCII to UCS-2 string
function atou(str) {
    return decodeURIComponent(escape(window.atob(str)));
}
// Usage:
utoa('✓ à la mode'); // 4pyTIMOgIGxhIG1vZGU=
atou('4pyTIMOgIGxhIG1vZGU='); // "✓ à la mode"

utoa('I \u2661 Unicode!'); // SSDimaEgVW5pY29kZSE=
atou('SSDimaEgVW5pY29kZSE='); // "I ♡ Unicode!"

这是一个helper funktion来编码到base64url:

base64url (s) {
        var to64url = btao(s);
         // Replace non-url compatible chars with base64url standard chars and remove leading =
        return to64url.replace(/\+/g, '_').replace(/\//g, '-').replace(/=+$/g, '');
    }

从这里开始:

/**
*
*  Base64 encode / decode
*  http://www.webtoolkit.info/
*
**/
var Base64 = {

    // private property
    _keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",

    // public method for encoding
    encode : function (input) {
        var output = "";
        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
        var i = 0;

        input = Base64._utf8_encode(input);

        while (i < input.length) {

            chr1 = input.charCodeAt(i++);
            chr2 = input.charCodeAt(i++);
            chr3 = input.charCodeAt(i++);

            enc1 = chr1 >> 2;
            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
            enc4 = chr3 & 63;

            if (isNaN(chr2)) {
                enc3 = enc4 = 64;
            } else if (isNaN(chr3)) {
                enc4 = 64;
            }

            output = output +
            this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +
            this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);
        }
        return output;
    },

    // public method for decoding
    decode : function (input) {
        var output = "";
        var chr1, chr2, chr3;
        var enc1, enc2, enc3, enc4;
        var i = 0;

        input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

        while (i < input.length) {

            enc1 = this._keyStr.indexOf(input.charAt(i++));
            enc2 = this._keyStr.indexOf(input.charAt(i++));
            enc3 = this._keyStr.indexOf(input.charAt(i++));
            enc4 = this._keyStr.indexOf(input.charAt(i++));

            chr1 = (enc1 << 2) | (enc2 >> 4);
            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
            chr3 = ((enc3 & 3) << 6) | enc4;

            output = output + String.fromCharCode(chr1);

            if (enc3 != 64) {
                output = output + String.fromCharCode(chr2);
            }
            if (enc4 != 64) {
                output = output + String.fromCharCode(chr3);
            }
        }

        output = Base64._utf8_decode(output);

        return output;
    },

    // private method for UTF-8 encoding
    _utf8_encode : function (string) {
        string = string.replace(/\r\n/g,"\n");
        var utftext = "";

        for (var n = 0; n < string.length; n++) {

            var c = string.charCodeAt(n);

            if (c < 128) {
                utftext += String.fromCharCode(c);
            }
            else if((c > 127) && (c < 2048)) {
                utftext += String.fromCharCode((c >> 6) | 192);
                utftext += String.fromCharCode((c & 63) | 128);
            }
            else {
                utftext += String.fromCharCode((c >> 12) | 224);
                utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                utftext += String.fromCharCode((c & 63) | 128);
            }
        }
        return utftext;
    },

    // private method for UTF-8 decoding
    _utf8_decode : function (utftext) {
        var string = "";
        var i = 0;
        var c = c1 = c2 = 0;

        while ( i < utftext.length ) {

            c = utftext.charCodeAt(i);

            if (c < 128) {
                string += String.fromCharCode(c);
                i++;
            }
            else if((c > 191) && (c < 224)) {
                c2 = utftext.charCodeAt(i+1);
                string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
                i += 2;
            }
            else {
                c2 = utftext.charCodeAt(i+1);
                c3 = utftext.charCodeAt(i+2);
                string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
                i += 3;
            }
        }
        return string;
    }
}

此外,搜索“JavaScript base64 encoding”会出现许多其他选项,上面是第一个。

这是一个atob()和btoa() JavaScript内置函数的现场演示:

<!DOCTYPE html>
<html>
  <head>
    <style>
      textarea{
        width:30%;
        height:100px;
      }
    </style>
    <script>
      // encode string to base64
      function encode()
      {
        var txt = document.getElementById("txt1").value;
        var result = btoa(txt);
        document.getElementById("txt2").value = result;
      }
      // decode base64 back to original string
      function decode()
      {
        var txt = document.getElementById("txt3").value;
        var result = atob(txt);
        document.getElementById("txt4").value = result;
      }
    </script>
  </head>
  <body>
    <div>
      <textarea id="txt1">Some text to decode
      </textarea>
    </div>
    <div>
      <input type="button" id="btnencode" value="Encode" onClick="encode()"/>
    </div>
    <div>
      <textarea id="txt2">
      </textarea>
    </div>
    <br/>
    <div>
      <textarea id="txt3">U29tZSB0ZXh0IHRvIGRlY29kZQ==
      </textarea>
    </div>
    <div>
      <input type="button" id="btndecode" value="Decode" onClick="decode()"/>
    </div>
    <div>
      <textarea id="txt4">
      </textarea>
    </div>
  </body>
</html>

对于更新的浏览器编码Uint8Array到字符串,并解码字符串到Uint8Array。

const base64 = {
    decode: s => Uint8Array.from(atob(s), c => c.charCodeAt(0)),
    encode: b => btoa(String.fromCharCode(...new Uint8Array(b)))
};

对于Node.js,你可以使用以下代码将string、Buffer或Uint8Array编码为string,并从string、Buffer或Uint8Array解码为Buffer。

const base64 = {
    decode: s => Buffer.from(s, 'base64'),
    encode: b => Buffer.from(b).toString('base64')
};