convertForTumblr.js

var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
function base64_decode(input){
    var output = new Array();
    var chr1, chr2, chr3;
    var enc1, enc2, enc3, enc4;
    var i = 0;

    var orig_input = input;
    input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
    if (orig_input != input)
        alert ("Warning! Characters outside Base64 range in input string ignored.");
    if (input.length % 4) {
        alert ("Error: Input length is not a multiple of 4 bytes.");
        return "";
    }
    
    var j=0;
    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[j++] = chr1;
        if (enc3 != 64)
          output[j++] = chr2;
        if (enc4 != 64)
          output[j++] = chr3;
          
    }
    return output;
}

// takes hex data with no seperator
function convert(data){
	
	// Now that we have raw hex data lets convert it
	// Each hex value is 2 characters
	var newhex = '';
	for(var i=0; i < data.length; i+=2){
		
		var substr = data.substr(i, 2);
		var val = parseInt(substr, 16);	
		
		if ((val <=46 && val >= 45) || (val <=57 && val >= 48) || (val <=90 && val >= 65) || (val == 95) || (val <=122 && val >= 97)) {
			newhex += String.fromCharCode(val);
		}else{
			newhex += '%' + substr.toUpperCase();
		}		
		
	}
	
	// dont convert tildes
	newhex = newhex.replace(/\%7E/g,'~');

	return newhex;
}

// http://tomeko.net/online_tools/base64.php
// Base64 to hex
var hD='0123456789ABCDEF';
function dec2hex(d){
    var h = hD.substr(d&15,1);
    while (d>15) {
        d>>=4;
        h=hD.substr(d&15,1)+h;
    }
    return h;
}

function convertForTumblr(imgURI,sep){
    var output = base64_decode(imgURI);
    var separator = "";
    if (sep){separator = "\\x";}
    var hexText = "";
    for (i=0; i<output.length; i++) {
      hexText = hexText + separator + (output[i]<16?"0":"") + dec2hex(output[i]);
    }
    
    var tumblrImage = convert(hexText);
    
    return tumblrImage;

}

img = convertForTumblr(base64image,false);