α-wwwiki

α-wwwiki :: history/mandel/20130927-194337.txt

editor : alpha [82.249.219.106] 2013/09/27 19:43:37
{canvas 
   {@ id="mycanvas" width="420"; height="420" style="background:#ffe;
      border:1px dashed black; box-shadow:0 0 24px black;"}}

{div {@ style="position:relative; top:0px; left:0px; 
      width:130px; display:inline-block; vertical-align:top;
      white-space:pre-wrap; font:normal 0.8em courier;" }
iterations [1,.[
{input {@ id="iter" type="text" value="10" style="background:#ccc; width:100px; text-align:center;"}}
zoom [1..1.e-11]
{input {@ id="zoom" type="text" value="4" style="background:#ccc; width:150px; text-align:center;"}}
{span {@ id="info"}time :}
x0 :
{span {@ id="x0"}0}
y0 :
{span {@ id="y0"}0}
{input {@ id="code" type="submit" value="load code" onclick="°°

var MANDEL = (function () { // the only one global var

var ctx,    // global 2D context
    iter,   // can be edited by field
    zoom,   // can be edited by field and by mouse
    x0, y0; // modified by mouse

function init () {
   var canvas = getId( 'mycanvas' );
   ctx = canvas.getContext( '2d' );
   getId('reset').addEventListener( 'click', this.reset );
   getId('update').addEventListener( 'click', this.update );
   add_zoom_to_mouse( canvas );
   getId('iter').value = iter = 10;
   getId('zoom').value = zoom = 4;
   x0 = 0;
   y0 = 0;
   compute_imageData();
}

function reset () {
   getId('iter').value = iter = 10;
   getId('zoom').value = zoom = 4;
   getId('x0').innerHTML = x0 = 0;
   getId('y0').innerHTML = y0 = 0;
   compute_imageData();
}

function update () { // called by the update button
   iter = getId('iter').value;
   zoom = getId('zoom').value;
   compute_imageData();
}

/////////////////////////////
// ADD ZOOM TO MOUSE
/////////////////////////////

function add_zoom_to_mouse ( can ) {

var context = can.getContext( '2d' );
var flag = false, coords, z, zmin = 50;

can.getMouse = function (event) {
  var totalOffsetX = 0,
      totalOffsetY = 0,
      canvasX = 0,
      canvasY = 0;
  var currentElement = this; // recursive search
  do { totalOffsetX += currentElement.offsetLeft;
       totalOffsetY += currentElement.offsetTop; 
  } while(currentElement = currentElement.offsetParent)
  canvasX = event.pageX - totalOffsetX;
  canvasY = event.pageY - totalOffsetY;
  return {x:canvasX, y:canvasY};
};

can.onmouseover = function(e) { 
   this.style.cursor = 'crosshair'; 
};

can.onmouseout  = function(e) { 
   this.style.cursor = 'default'; 
};

can.onmousedown = function (e) {
   iter = parseInt(getId('iter').value);
   var zoom_prev = zoom;
   zoom = parseFloat(getId('zoom').value);
   x0 = x0*zoom_prev/zoom;
   y0 = y0*zoom_prev/zoom;
   coords = this.getMouse( e );
   x0 =   coords.x/this.width  - 0.5  + x0;
   y0 = -(coords.y/this.height - 0.5) + y0;
   getId('x0').innerHTML = x0;
   getId('y0').innerHTML = y0;
   context.strokeStyle = '#888'; 
   context.lineWidth = 1;
   // context.globalCompositeOperation = 'xor';
   z = zmin;
   flag = true;
};

can.onmousemove = function (e) {
   if (!flag) return;
   var coords_2 = this.getMouse( e );
   var w = Math.abs( coords_2.x - coords.x );
   var h = Math.abs( coords_2.y - coords.y );
   z = Math.max( w, h );
   context.strokeRect( coords.x - z/2, coords.y - z/2, z, z );
};

can.onmouseup = function (e) {
   var zoom_prev = zoom;
   z = (z< zmin)? zmin : z;
   zoom = zoom*z/this.width;
   getId('zoom').value = zoom;
   x0 = x0*zoom_prev/zoom;
   y0 = y0*zoom_prev/zoom;
   flag = false;
   compute_imageData();
};

} // end add_mouse_zoom_to ( canvas )

/////////////////////////////
// MANDEL
/////////////////////////////

var count, norme; // shared by mandel_geo and mandel_col

function mandel_geo( cx, cy ) { // compute k at point C
   var x = 0.0, y = 0.0; // initialyze z = x + iy = 0
   for (count = 0; count < iter; count++) {
      var X = x*x - y*y + cx; // compute z = z^2 + c
      var Y = 2*x*y + cy;
      norme = X*X + Y*Y;
      if ( norme > 4.0 )	
         break; // exit if norme > 2
      x = X; // update z = x +iy
      y = Y;
   }
}

/*
function _mandel_col( rgba ) {
   if ( count < iter ) {
      rgba.r = ( count%2 == 0 )? 255 : 0;
      rgba.g = ( count%2 == 0 )? 0 : 255;
      rgba.b = 0;
   } else {
      rgba.r = 0;
      rgba.g = 255;
      rgba.b = 255; // Math.random() * 256 | 0;
   }
}
*/

return {init:init, update:update, reset:reset};

})().init(); // MANDEL is created then inited

°°"}}
{input {@ id="update" type="submit" value="update"}} 
{input {@ id="reset" type="submit" value="reset"}}
}
_h3 Using mandel
_ul {b 1)} First, click on "load code" to init the code,
_ul {b 2)} edit the fields "iterations" and "zoom", then click on "update",
_ul {b 3)} you can mouse-draw a rect around any point in the canvas to define a zoom around it, or click any point to get a predefined zoom in,
_ul {b 4)} click on "reset" to re-initialize mandel.

_h3 links
_ul [[maelstrom|http://www.youtube.com/watch?v=I9FTyXnq5z8]], Kalles Fractaler with bigInts,
_ul [[http://www.syti.net/Fractals.html|http://www.syti.net/Fractals.html]]

_h3 note

_p L'étonnant ensemble de [[Mandelbrot|../alphawiki/?view=mandel]] est construit sur une expression simplissime : {b z=z{sup 2}+c}, où z et c sont des nombres "dits" complexes (de la forme : {b x+iy}). Pour le cas où {b c=-1}, cette expression se réduit à : {b z=z{sup 2}-1} qui peut s'écrire : {b z{sup 2}-z-1=0}. Une équation du second degré dont les deux racines réelles (voir [[equation]]) sont les deux valeurs du nombre d'OR : {b 1.618 et 0.618}. 
_p The golden ratio is in the mandel set !

_h3 links
_ul [[Fractals-in-theory-and-practice|http://www.codeproject.com/Articles/650821/Fractals-in-theory-and-practice]]
_ul [[Vortex Based Math & the 360˚ Circle|http://www.youtube.com/watch?v=-Rrsm4aMUgE&feature=youtube_gdata_player]]