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<html>
<head>
<title>Compress colors using VQ</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
@import "../../../dojo/resources/dojo.css";
@import "../../../dijit/tests/css/dijitTests.css";
.pane { margin-top: 2em; }
</style>
<script type="text/javascript" src="../../../dojo/dojo.js" djConfig="isDebug: true"></script>
<script type="text/javascript">
dojo.require("dojox.encoding.tests.colors");
dojo.require("dojox.encoding.splay");
dojo.require("dojox.encoding.bits");
var colors = dojox.encoding.tests.colors;
var dist = function(a, b){
var r = a[0] - b[0], g = a[1] - b[1], b = a[2] - b[2];
return r * r + g * g + b * b;
};
var hexcolor = function(c){
return "#" + (c[0] < 16 ? "0" : "") + c[0].toString(16) +
(c[1] < 16 ? "0" : "") + c[1].toString(16) +
(c[2] < 16 ? "0" : "") + c[2].toString(16);
};
var maxdist = function(a, b, maxdist){
var r = Math.abs(a[0] - b[0]), g = Math.abs(a[1] - b[1]), b = Math.abs(a[2] - b[2]);
++maxdist[bits(r)];
++maxdist[bits(g)];
++maxdist[bits(b)];
};
var encodeColor = function(a, b, splay, stream){
var r = a[0] - b[0], g = a[1] - b[1], b = a[2] - b[2];
stream.putBits(r < 0 ? 1 : 0, 1);
splay.encode(Math.abs(r), stream);
stream.putBits(g < 0 ? 1 : 0, 1);
splay.encode(Math.abs(g), stream);
stream.putBits(b < 0 ? 1 : 0, 1);
splay.encode(Math.abs(b), stream);
};
var bits = function(x){
var w = 1;
for(var v = 2; x >= v; v <<= 1, ++w);
return w;
};
var runVQ = function(n){
dojo.byId("status").innerHTML = "<em>Initializing...</em>";
dojo.byId("report").innerHTML = "<em>Running VQ...</em>";
var clusters = [];
// select initial cluster centers
var empty = {};
for(var i in colors){
if(i in empty){ continue; }
clusters.push({center: colors[i]});
if(clusters.length == n){ break; }
}
/*
for(var i = 0; i < n; ++i){
var r = Math.floor(Math.random() * 256), g = Math.floor(Math.random() * 256), b = Math.floor(Math.random() * 256);
clusters.push({center: [r, g, b]});
}
*/
// do runs
dojo.byId("status").innerHTML = "<div>Starting runs...</div>";
var jitter = 0, niter = 1;
do {
// save previous centers
var old_clusters = [];
dojo.forEach(clusters, function(c){ old_clusters.push({center: c.center}); c.members = []; });
// assign colors to clusters
for(var i in colors){
if(i in empty){ continue; }
var c = colors[i], k = -1, kd = Number.MAX_VALUE;
for(var j = 0; j < clusters.length; ++j){
var jd = dist(clusters[j].center, c);
if(jd < kd){ k = j, kd = jd; }
}
clusters[k].members.push(i);
}
// recalculate cluster centers
for(var i = 0; i < clusters.length; ++i){
if(!clusters[i].members.length){ continue; }
var r = 0, g = 0, b = 0;
dojo.forEach(clusters[i].members, function(name){
var c = colors[name];
r += c[0];
g += c[1];
b += c[2];
});
r = Math.round(r / clusters[i].members.length);
g = Math.round(g / clusters[i].members.length);
b = Math.round(b / clusters[i].members.length);
clusters[i].center = [r, g, b];
}
// calculate the jitter
jitter = 0;
for(var i = 0; i < clusters.length; ++i){
jitter = Math.max(jitter, dist(clusters[i].center, old_clusters[i].center));
}
var node = dojo.doc.createElement("div");
node.innerHTML = "Run #" + niter + ", jitter = " + jitter;
dojo.byId("status").appendChild(node);
++niter;
}while(jitter > 1 && niter < 1000);
// calculate the required number of bytes
var output = new dojox.encoding.bits.OutputStream(),
splay = new dojox.encoding.Splay(256);
for(var i = 0; i < clusters.length; ++i){
var c = clusters[i], m = c.members, d = 0, ol = output.getWidth();
output.putBits(c.center[0], 8);
output.putBits(c.center[1], 8);
output.putBits(c.center[2], 8);
splay.init();
c.maxdist = [0, 0, 0, 0, 0, 0, 0, 0, 0];
for(var j = 0; j < m.length; ++j){
var color = colors[m[j]];
maxdist(c.center, color, c.maxdist);
encodeColor(c.center, color, splay, output);
}
c.bits = output.getWidth() - ol;
}
var node = dojo.doc.createElement("div");
node.innerHTML = "Required " + Math.ceil(output.getWidth() / 8) + " bytes";
dojo.byId("status").appendChild(node);
// generate color tables
var reps = [];
for(var i = 0; i < clusters.length; ++i){
var c = clusters[i], m = c.members;
reps.push("<p>Cluster #" + i + " contains " + m.length + " members. Length histogram:");
for(var j = 0; j < c.maxdist.length; ++j){
if(c.maxdist[j]){
reps.push(" " + j + "&mdash;" + c.maxdist[j]);
}
}
reps.push(". It requires " + c.bits + " bits (" + Math.ceil(c.bits / 8) + " bytes) to be encoded.</p>");
reps.push("<table>");
var wd = dist([255,255,255], c.center), bd = dist([0,0,0], c.center);
reps.push("<tr><td style='background: " + hexcolor(c.center) + "; color: " +
(wd < bd ? "black" : "white") + "'><strong>CENTER</strong></td><td>" +
c.center[0] + "</td><td>" + c.center[1] + "</td><td>" + c.center[2] + "</td></tr>");
for(var j = 0; j < m.length; ++j){
var color = colors[m[j]];
wd = dist([255,255,255], color);
bd = dist([0,0,0], color);
reps.push("<tr><td style='background: " + m[j] + "; color: " +
(wd < bd ? "black" : "white") + "'><strong>" + m[j] + "</strong></td><td>" +
color[0] + "</td><td>" + color[1] + "</td><td>" + color[2] + "</td></tr>");
}
reps.push("</table>");
}
dojo.byId("report").innerHTML = reps.join("\n");
};
run = function(){
var n = parseInt(dojo.byId("ncluster").value);
runVQ(n);
};
dojo.addOnLoad(function(){
dojo.connect(dojo.byId("run"), "onclick", run);
});
</script>
</head>
<body>
<h1>Compress colors using VQ</h1>
<p>Select desirable number of clusters:&nbsp;<select id="ncluster">
<option value="1">1</option>
<option value="2">2</option>
<option value="4">4</option>
<option value="8">8</option>
<option value="16">16</option>
<option value="32">32</option>
<option value="64">64</option>
</select>&nbsp;<button id="run">Run</button></p>
<div id="status" class="pane"><em>No status yet.</em></div>
<div id="report" class="pane"><em>No results yet.</em></div>
</body>
</html>

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