Canvas Renderer

canvasrenderer.py

#!/usr/bin/env python

import sys
import json
import base64

try:
	import WebKit
	view = WebKit.WebView.alloc().init()
	wso = view.windowScriptObject()
	evalJS = wso.evaluateWebScript_
except:
	import webkit
	import gtk
	gtk.gdk.threads_init()
	view = webkit.WebView()
	def evalJS(js):
		view.execute_script ('document.title=eval(' + json.dumps(js, False, False) + ')')
		return view.get_main_frame().get_title()

if len(sys.argv) > 1:
	input = open(sys.argv[1], 'r')
else:
	input = sys.stdin

result = json.loads(unicode(evalJS(u'''(function() {
	
	var canvas, ctx, files = [], w, h;
	function newFile(aw, ah) {
		canvas = document.createElement('canvas');
		ctx = canvas.getContext('2d');
		canvas.width = w = aw;
		canvas.height = h = ah;
	}
	function saveFile(filename) {
		if (filename === undefined) filename = 'Untitled';
		files.push ([filename, canvas.toDataURL()]);
	}

	newFile (1, 1);

	try {
		eval (''' + json.dumps(input.read(), True, False) + u''');
	} catch (e) {
		return JSON.stringify(['error', e.toString()]);
	}
	return JSON.stringify(['success', files]);

})() + '';''')));

if result[0] == 'error':
	sys.stderr.write ('Error in your code: ' + result[1] + '\n')
else:
	for file in result[1]:
		print 'Writing file ' + file[0] + '.png'
		fp = open(file[0] + '.png', 'wb')
		fp.write (base64.b64decode(file[1][file[1].index(',') + 1:]))
		fp.close ()

test.js

newFile (200, 100);

var gradient = ctx.createLinearGradient(0, 0, 0, h);
gradient.addColorStop (0, '#f00');
gradient.addColorStop (1, '#ff0');

ctx.fillStyle = gradient;
ctx.fillRect (0, 0, w, h);

ctx.fillStyle = '#fff';
ctx.font = 'bold 15pt Verdana';
ctx.textAlign = 'center';
ctx.textBaseLine = 'middle';

ctx.shadowColor = 'black';
ctx.shadowBlur = 10;
ctx.shadowOffsetY = 3;
ctx.fillText ('Hello World!', w / 2, h / 2);

saveFile ('test');