img.js

/**
 * This is simple transfer image to data uri(base64 encode) nodejs command line tool
 *
 * require
 *     install nodejs v0.8+
 *
 * how to use
 *     node img YOUR_IMAGE_FILE_PATH
 *
 * sample
 *     node img logo.png
 *
 */

var param = process.argv[2],
    sp = param.split(/\./ig),
    fs = require('fs');

console.log('File name: ', param, sp[sp.length-1]);
console.log('============================== BEGIN =================================');

fs.readFile( param , function(err, data) {
    var base64data = new Buffer(data).toString('base64'),
        imgString = 'data:image/' + sp[sp.length-1] + ';base64,' + base64data;

    // copy to clipboard
    pbcopy(imgString);

    console.log(imgString);
    console.log('============================== END =================================');
});


/**
 * copy string to clipboard
 * mac only
 *
 * @param  {String} data put string to clipboard
 * @return {String}      return original param
 */
function pbcopy(data) {
    var proc = require('child_process').spawn('pbcopy');
        proc.stdin.write(data);
        proc.stdin.end();

    return data;
}