A encryptor used for http://puzzling.stackexchange.com/questions/12481/a-row-of-two-colored-circles/12566

imagecrypt.js

function encript(current, previous) {
	previous = previous || 0;
	return (current + previous)%27;
}

var Canvas = require("canvas");
var fs = require("fs");
var source = process.argv[2];
//---PREPARE---
source = source.toUpperCase();
source = source.split("");
var charA = "A".charCodeAt(0);
for(var i in source) {
	if(source[i] >= "A" && source[i] <= "Z")
		source[i] = source[i].charCodeAt(0) - charA + 1;
	else
		source[i] = 0;
}
//----CRYPT----
var encripted = [];
for(var i in source) {
	encripted[i] = encript(source[i], source[i-1]);
}
//----IMAGE----
var CSIZE = 20;
var CMARGIN = 10;
var canvas = new Canvas(encripted.length*(CSIZE*2+CMARGIN) + 30,CSIZE*2+20);
var context = canvas.getContext("2d");
context.beginPath();
context.moveTo(0, canvas.height/2);
context.lineTo(canvas.width, canvas.height/2);
context.lineWidth = 2;
context.stroke();
context.closePath();
context.lineWidth = 1;
for(var i in encripted) {
	var red_a = encripted[i] & 1;
	var green_a = encripted[i] & 2;
	var blue_a = encripted[i] & 4;
	var color_a = "rgba(" + red_a*255 + ", " + green_a*255 + ", " + blue_a*255 + ", 1)";

	context.beginPath();
	context.fillStyle = color_a;
	context.arc((1*i + 0.5)*(CSIZE*2+CMARGIN) + 30, 10 + CSIZE, CSIZE, Math.PI/2, Math.PI*3/2, false);
	context.stroke();
	context.fill();
	context.closePath();

	var red_b = encripted[i] & 8;
	var green_b = encripted[i] & 16;
	var blue_b = encripted[i] & 4;
	var color_b = "rgba(" + red_b*255 + ", " + green_b*255 + ", " + blue_b*255 + ", 1)";

	context.beginPath();
	context.fillStyle = color_b;
	context.arc((1*i + 0.5)*(CSIZE*2+CMARGIN) + 30, 10 + CSIZE, CSIZE, Math.PI/2, Math.PI*3/2, true);
	context.stroke();
	context.fill();
	context.closePath();
}
var buffer = canvas.toBuffer();
fs.writeFile("./image_"+Math.round(Math.random()*36*36).toString(36)+".png", buffer);
//----PRINT----
for(var i in encripted) {
	if(encripted[i] != 0)
		encripted[i] = String.fromCharCode(encripted[i]%27 + charA - 1);
	else
		encripted[i] = " ";
}
console.log(encripted.join(""))