////============================================
//// expo15.js, 05/04/09, by ralph abraham
//// coloring by distance

//// GLOBAL VARS

	var c = 0.90; // dorband control parameter
	
	// hardwired init point, world coords
	// upper left corner of unit square of the u-v plane
	var u0 = 0.3; // init u
	var v0 = 0.8; // init v 
	// hardwired init point, screen coords
	var x0 = screenx(u0);
	var y0 = screeny(v0);
	
	// to setup 2D world coords (u, v) ranges
	// init values determined by canvas size
	var wumax = 1.0; // worldu max
	var wumin = 0; // worldu min
	var wvmax = 1.0; // worldv max
	var wvmin = 0; // worldv min
	// and screen coords (x, y) ranges
	var sxmax = 320; // screenx max, use width of canvas from HTML page
	var sxmin = 0; // screenx min
	var symax = 280; // screeny max, use height of canvas from HTML page
	var symin = 0; // screeny min
	
	// color spectrum 03 as an array of strings
	var a = new Array();
	a[0] = "red";
	a[1] = "#FF8000";
	a[2] = "yellow";
	a[3] = "#80FF00";
	a[4] = "lime";
	a[5] = "#00FF80";
	a[6] = "cyan";
	a[7] = "#0080FF";
	a[8] = "blue";
	a[9] = "#8000FF";
	a[10] = "magenta";
	a[11] = "#FF0080";
	a[12] = "white"; // for overscale
	a[13] = "white";
	a[14] = "white";

//// MATH FUNCS 

	// map screen to world coords, x --> u
	function worldu(sx) {
		var temp =  ( sx - sxmin ) / ( sxmax - sxmin );
		return wumin + ( wumax - wumin ) * temp;
	};

	// map screen to world coords, y --> v
	function worldv(sy) {
		var temp =  ( sy - symin ) / ( symax - symin );
		return wvmax - ( wvmax - wvmin ) * temp;
	};
	
	//// MATH FUNCS world (u, v) --> screen (x, y)

	function screenx(wu) {
		return 320 * wu;
	};
	
	function screeny(wv) {
		return 280 - 280 * wv;
	};

	// euclidean plane distance for world coords
	function dist(u1, v1, u2, v2) {
		var du2 = (u1 - u2) * (u1 - u2);
		var dv2 = (v1 - v2) * (v1 - v2);
		return Math.sqrt(du2 + dv2);
	};

//// here is the dorband map
	function dorbandu(u, v) {
		return (1 - c) * u + 4 * c * v * (1 - v);
	};

	function dorbandv(u, v) {
		return (1 - c) * v + 4 * c * u * (1 - u);
	};
	
//// SETUP

	// wait for the browser to load
	window.onload = function() {
	// set up background basic template
		base00(); // draw entire canvas
		drawblot(x0, y0, 2, "white"); // 10 is size of blot
	};
	
    // setup single white canvas
	function base00()  {
		var canvas = document.getElementById("canvas"); // only one canvas
		var ctx = canvas.getContext("2d");
		// setup whole rectangle (x0, y0, width, height)
		ctx.clearRect(0, 0, 320, 280);
 		ctx.fillStyle = "black"; //  bg color
 		ctx.fillRect (0, 0, 320, 280);
	};
	
	// draw a blot from upper corner (x, y), height and width w, color c
	function drawblot(x, y, w, c) {
		var canvas = document.getElementById("canvas"); // only one canvas
		var ctx = canvas.getContext("2d");
		//ctx.clearRect(x, y, w, w);
 		ctx.fillStyle = c; //  colored rect
 		ctx.fillRect (x, y, w, w);
	};

//// declare and init vars for iteration
  	var unow = u0;
  	var vnow = v0;
  	var unext = (1 - c) * unow; // temp version of dorband map
  	var vnext = (1 - c) * vnow;
  	var xnext = screenx(unext);
  	var ynext = screeny(vnext);
  	
    // this is for interaction (expo14)
	document.onclick = function(ev) { // to step the map
		//alert("got click");
  		unext = dorbandu(unow, vnow); // apply the dorband map
  		vnext = dorbandv(unow, vnow);
  		//alert("got next u-v");
  		xnext = screenx(unext); // get screen coords
  		ynext = screeny(vnext);
  		var temp1 = dist(unow, vnow, unext, vnext);
  		var temp2 = Math.floor(10 * temp1);
		drawblot(xnext, ynext, 2, a[temp2]); // draw next point
		unow = unext; // now step the map
		vnow = vnext;
	};

////////// END ///////////