The designer gave me SVG images exported from PhotoShop, which cannot be supported by Android Studio. So I wrote this script to convert SVG to PNGs of different sizes needed in Android projects.

svg2png.js

#!/usr/bin/phantomjs

var fs = require('fs');
var system = require('system');
var webPage = require('webpage');

var args = system.args;

if (args.length != 4) {
  console.error('ERROR: Please specify 3 arguments: [input svg file], [res directory] and [output image width (mdpi)].');
  phantom.exit();
}

var arg0 = args[1]; // input file
var arg1 = args[2]; // output res/
var arg2 = args[3]; // image width for mdpi

var ratios = {
  'drawable-ldpi': 0.75,
  'drawable-mdpi': 1,
  'drawable-hdpi': 1.5,
  'drawable-xhdpi': 2,
  'drawable-xxhdpi': 3,
  'drawable-xxxhdpi': 4
};

var fileBaseName = arg0.substring(arg0.lastIndexOf('/'), arg0.lastIndexOf('.'));

var outputs = fs.list(arg1).filter(function (name) {
  return ratios.hasOwnProperty(name);
});

var content = fs.read(arg0);
var parser = new DOMParser();
var svgDoc = parser.parseFromString(content, 'image/svg+xml');
var root = svgDoc.rootElement;
if (!root || root.tagName.toLowerCase() !== 'svg') {
  console.error('ERROR: No valid SVG file supplied.');
  phantom.exit();
}
var vb = root.getAttribute('viewBox');
if (!vb) {
  console.error('ERROR: ViewBox not specified in SVG.');
  phantom.exit();
}
var vbp = vb.split(/\s+/g).map(function (item) { return parseFloat(item); });
var w = parseFloat(root.getAttribute('width'));
var h = parseFloat(root.getAttribute('height'));
if (isNaN(w) || isNaN(h)) {
  console.error('ERROR: Width/height not specified in SVG.');
  phantom.exit();
}
if (vbp.length !== 4 || vbp[0] !== 0 || vbp[1] !== 0 || vbp[2] !== w || wbp[3] !== h) {
  console.warn('WARNING: ViewBox does not match width/height specifications.');
}

var mdpiW = parseFloat(arg2);
if (isNaN(mdpiW)) {
  console.error('ERROR: Wrong output width specified.');
  phantom.exit();
}
var mdpiH = mdpiW * h / w;
console.log('INFO: source width is ' + w + ', height is ' + h + '.');

var finishedFlags = outputs.map(function () { return false; })

outputs.forEach(function (output, index) {
  var ratio = ratios[output];
  var tw = Math.round(mdpiW * ratio);
  var th = Math.round(mdpiH * ratio);
  root.setAttribute('width', tw);
  root.setAttribute('height', th);
  var xmls = new XMLSerializer();
  var page = webPage.create();
  page.viewportSize = { width: tw, height: th };
  page.open('data:image/svg+xml;base64,' + window.btoa(xmls.serializeToString(svgDoc)), function (status) {
    page.render(arg1 + '/' + output + fileBaseName  + '.png', { format: 'png' });
    finishedFlags[index] = true;
    console.log('INFO: Output ' + tw + 'x' + th + ' image to ' + output + fileBaseName + '.png.');
    if (finishedFlags.every(function (item) { return item; })) {
      phantom.exit();
    }
  })
});