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。
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
如果你需要编码一个HTML图像对象,你可以写一个简单的函数,像这样:
function getBase64Image(img) {
var canvas = document.createElement("canvas");
canvas.width = img.width;
canvas.height = img.height;
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0);
var dataURL = canvas.toDataURL("image/png");
// escape data:image prefix
return dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
// or just return dataURL
// return dataURL
}
通过id获取图像的Base64编码:
function getBase64ImageById(id){
return getBase64Image(document.getElementById(id));
}
还有更多。
其他回答
这是一个缩小的填充窗口。Atob + window.btoa:
(function(){function t(t){this.message=t}var e="undefined"!=typeof exports?exports:this,r="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";t.prototype=Error(),t.prototype.name="InvalidCharacterError",e.btoa||(e.btoa=function(e){for(var o,n,a=0,i=r,c="";e.charAt(0|a)||(i="=",a%1);c+=i.charAt(63&o>>8-8*(a%1))){if(n=e.charCodeAt(a+=.75),n>255)throw new t("'btoa' failed: The string to be encoded contains characters outside of the Latin1 range.");o=o<<8|n}return c}),e.atob||(e.atob=function(e){if(e=e.replace(/=+$/,""),1==e.length%4)throw new t("'atob' failed: The string to be decoded is not correctly encoded.");for(var o,n,a=0,i=0,c="";n=e.charAt(i++);~n&&(o=a%4?64*o+n:n,a++%4)?c+=String.fromCharCode(255&o>>(6&-2*a)):0)n=r.indexOf(n);return c})})();
(function (root, factory) {
if (typeof define === 'function' && define.amd) {
// AMD. Register as an anonymous module.
define([], function() {factory(root);});
} else factory(root);
// node.js has always supported base64 conversions, while browsers that support
// web workers support base64 too, but you may never know.
})(typeof exports !== "undefined" ? exports : this, function(root) {
if (root.atob) {
// Some browsers' implementation of atob doesn't support whitespaces
// in the encoded string (notably, IE). This wraps the native atob
// in a function that strips the whitespaces.
// The original function can be retrieved in atob.original
try {
root.atob(" ");
} catch(e) {
root.atob = (function(atob) {
var func = function(string) {
return atob(String(string).replace(/[\t\n\f\r ]+/g, ""));
};
func.original = atob;
return func;
})(root.atob);
}
return;
}
// base64 character set, plus padding character (=)
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
// Regular expression to check formal correctness of base64 encoded strings
b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;
root.btoa = function(string) {
string = String(string);
var bitmap, a, b, c,
result = "", i = 0,
rest = string.length % 3; // To determine the final padding
for (; i < string.length;) {
if ((a = string.charCodeAt(i++)) > 255
|| (b = string.charCodeAt(i++)) > 255
|| (c = string.charCodeAt(i++)) > 255)
throw new TypeError("Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.");
bitmap = (a << 16) | (b << 8) | c;
result += b64.charAt(bitmap >> 18 & 63) + b64.charAt(bitmap >> 12 & 63)
+ b64.charAt(bitmap >> 6 & 63) + b64.charAt(bitmap & 63);
}
// If there's need of padding, replace the last 'A's with equal signs
return rest ? result.slice(0, rest - 3) + "===".substring(rest) : result;
};
root.atob = function(string) {
// atob can work with strings with whitespaces, even inside the encoded part,
// but only \t, \n, \f, \r and ' ', which can be stripped.
string = String(string).replace(/[\t\n\f\r ]+/g, "");
if (!b64re.test(string))
throw new TypeError("Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.");
// Adding the padding if missing, for semplicity
string += "==".slice(2 - (string.length & 3));
var bitmap, result = "", r1, r2, i = 0;
for (; i < string.length;) {
bitmap = b64.indexOf(string.charAt(i++)) << 18 | b64.indexOf(string.charAt(i++)) << 12
| (r1 = b64.indexOf(string.charAt(i++))) << 6 | (r2 = b64.indexOf(string.charAt(i++)));
result += r1 === 64 ? String.fromCharCode(bitmap >> 16 & 255)
: r2 === 64 ? String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255)
: String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255, bitmap & 255);
}
return result;
};
});
完整版https://github.com/MaxArt2501/base64-js/blob/master/base64.js
基本上,我只是稍微清理了一下原始代码,这样JSLint就不会抱怨太多了,而且我把注释中标记为私有的方法实际上变成了私有的。我还添加了我在自己的项目中需要的两个方法,即decodeToHex和encodeFromHex。
代码:
var Base64 = (function() {
"use strict";
var _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var _utf8_encode = function (string) {
var utftext = "", c, n;
string = string.replace(/\r\n/g,"\n");
for (n = 0; n < string.length; n++) {
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;
};
var _utf8_decode = function (utftext) {
var string = "", i = 0, c = 0, c1 = 0, c2 = 0;
while ( i < utftext.length ) {
c = utftext.charCodeAt(i);
if (c < 128) {
string += String.fromCharCode(c);
i++;
} else if((c > 191) && (c < 224)) {
c1 = utftext.charCodeAt(i+1);
string += String.fromCharCode(((c & 31) << 6) | (c1 & 63));
i += 2;
} else {
c1 = utftext.charCodeAt(i+1);
c2 = utftext.charCodeAt(i+2);
string += String.fromCharCode(((c & 15) << 12) | ((c1 & 63) << 6) | (c2 & 63));
i += 3;
}
}
return string;
};
var _hexEncode = function(input) {
var output = '', i;
for(i = 0; i < input.length; i++) {
output += input.charCodeAt(i).toString(16);
}
return output;
};
var _hexDecode = function(input) {
var output = '', i;
if(input.length % 2 > 0) {
input = '0' + input;
}
for(i = 0; i < input.length; i = i + 2) {
output += String.fromCharCode(parseInt(input.charAt(i) + input.charAt(i + 1), 16));
}
return output;
};
var encode = function (input) {
var output = "", chr1, chr2, chr3, enc1, enc2, enc3, enc4, i = 0;
input = _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 += _keyStr.charAt(enc1);
output += _keyStr.charAt(enc2);
output += _keyStr.charAt(enc3);
output += _keyStr.charAt(enc4);
}
return output;
};
var decode = function (input) {
var output = "", chr1, chr2, chr3, enc1, enc2, enc3, enc4, i = 0;
input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
while (i < input.length) {
enc1 = _keyStr.indexOf(input.charAt(i++));
enc2 = _keyStr.indexOf(input.charAt(i++));
enc3 = _keyStr.indexOf(input.charAt(i++));
enc4 = _keyStr.indexOf(input.charAt(i++));
chr1 = (enc1 << 2) | (enc2 >> 4);
chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
chr3 = ((enc3 & 3) << 6) | enc4;
output += String.fromCharCode(chr1);
if (enc3 !== 64) {
output += String.fromCharCode(chr2);
}
if (enc4 !== 64) {
output += String.fromCharCode(chr3);
}
}
return _utf8_decode(output);
};
var decodeToHex = function(input) {
return _hexEncode(decode(input));
};
var encodeFromHex = function(input) {
return encode(_hexDecode(input));
};
return {
'encode': encode,
'decode': decode,
'decodeToHex': decodeToHex,
'encodeFromHex': encodeFromHex
};
}());
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, '');
}
下面是@user850789的AngularJS Factory版本:
'use strict';
var ProjectNameBase64Factory = angular.module('project_name.factories.base64', []);
ProjectNameBase64Factory.factory('Base64', function () {
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 +
Base64._keyStr.charAt(enc1) + Base64._keyStr.charAt(enc2) +
Base64._keyStr.charAt(enc3) + Base64._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 = Base64._keyStr.indexOf(input.charAt(i++));
enc2 = Base64._keyStr.indexOf(input.charAt(i++));
enc3 = Base64._keyStr.indexOf(input.charAt(i++));
enc4 = Base64._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 = 0, c2 = 0, c3 = 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;
}
};
return Base64;
});
虽然还有一些工作要做,但如果你想要一个高性能的本地解决方案,可以使用一些HTML5函数。
如果你可以把你的数据放到一个Blob中,那么你可以使用FileReader.readAsDataURL()函数来获得一个data:// URL,并砍掉它的前面来获得Base64数据。
你可能必须做进一步的处理,但urldecode数据,因为我不确定是否+字符转义或不为数据:// URL,但这应该是相当微不足道的。