the tool uses LZW lossless data compression algorithm(http://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch) to compress text field in salesforce. It does NOT work fully, and I ported Javascript algorithm into apex. 

For JS example:

// LZW-compress a string
function lzw_encode(s) {
    var dict = {};
    var data = (s + "").split("");
    var out = [];
    var currChar;
    var phrase = data[0];
    var code = 256;
    for (var i=1; i 1 ? dict[phrase] : phrase.charCodeAt(0));
            dict[phrase + currChar] = code;
            code++;
            phrase=currChar;
        }
    }
    out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
    for (var i=0; i