After experimenting with a long running average at maxed out FPS and a variety of map sizes, 128 seems to actually be a good size to use if only drawing bits of world with stuff in it. 64 actually did even better in some situations, but significantly worse in others (lots of land, zoomed out).
<!doctype html>
<html>
<head>
<title>Hedgewars Theme Editor</title>
<script type="text/javascript">
var sky, clouds, horizont, water, land, border;
var skyColor, waterTopColor, waterBottomColor;
var elements = 7;
var landArray;
function landFunction(x){
return 384 - 192 * Math.sin(x * Math.PI/512);
}
function tryToDraw(){
if (--elements <= 0) {
draw();
}
}
function load(){
var canvas = document.getElementById('preview');
if (canvas.getContext){
var ctx = canvas.getContext('2d');
ctx.fillStyle = '#0b294b';
ctx.fillRect(0, 0, 512, 384);
ctx.font = "40pt Arial";
ctx.fillStyle = '#2b7bd5';
ctx.fillText('Loading Images...', 32, 212);
}
sky = new Image();
sky.onload = tryToDraw;
sky.src = 'http://hedgewars.googlecode.com/hg/share/hedgewars/Data/Themes/Nature/Sky.png';
clouds = new Image();
clouds.onload = tryToDraw;
clouds.src = 'http://hedgewars.googlecode.com/hg/share/hedgewars/Data/Graphics/Clouds.png';
horizont = new Image();
horizont.onload = tryToDraw;
horizont.src = 'http://hedgewars.googlecode.com/hg/share/hedgewars/Data/Themes/Nature/horizont.png';
land = new Image();
land.onload = tryToDraw;
land.src = 'http://hedgewars.googlecode.com/hg/share/hedgewars/Data/Themes/Nature/LandTex.png';
border = new Image();
border.onload = tryToDraw;
border.src = 'http://hedgewars.googlecode.com/hg/share/hedgewars/Data/Themes/Nature/Border.png';
water = new Image();
water.onload = tryToDraw;
water.src = 'http://hedgewars.googlecode.com/hg/share/hedgewars/Data/Graphics/BlueWater.png';
landArray = new Array(512);
for (var x = 0; x < landArray.length; x++)
landArray[x] = landFunction(x);
skyColor = '#131252';
document.getElementById('skyColor').value = skyColor;
waterTopColor = '#555C9D';
document.getElementById('waterTopColor').value = waterTopColor;
waterBottomColor = '#343C7D';
document.getElementById('waterBottomColor').value = waterBottomColor;
tryToDraw();
}
function draw(){
var canvas = document.getElementById('preview');
if (canvas.getContext){
var ctx = canvas.getContext('2d');
ctx.fillStyle = skyColor;
ctx.fillRect(0, 0, 512, 384);
ctx.drawImage(sky, 0, 64, 512, 256);
for (var i = 0; i < 4; i++)
ctx.drawImage(clouds, 0, i * 128, 256, 128, i * 128, 64, 128, 64);
ctx.drawImage(horizont, 0, 192, 512, 128);
ctx.save();
ctx.beginPath();
ctx.moveTo(0, 384);
for (var x = 0; x < landArray.length; x++)
ctx.lineTo(x, landArray[x]);
ctx.clip();
for (var i = 0; i < 2; i++)
for (var k = 0; k < 2; k++)
ctx.drawImage(land, i * 320, k * 240, 320, 240);
ctx.restore();
var k = 0;
for (var x = 0; x < landArray.length; x++) {
if (++k == 64)
k = 0;
ctx.drawImage(border, k, 0, 2, 16, x, landArray[x] - 4, 1, 8);
}
var gradient = ctx.createLinearGradient(0, 320, 0, 384);
gradient.addColorStop(0, waterTopColor);
gradient.addColorStop(1, waterBottomColor);
ctx.fillStyle = gradient;
ctx.fillRect(0, 320, 512, 384);
for (var i = 0; i < 8; i++)
ctx.drawImage(water, i * 64, 308, 64, 24);
}
}
</script>
<style type="text/css">
canvas { border: 1px solid black; }
</style>
</head>
<body onload="load();">
<h1>Hedgewars Theme editor</h1>
<canvas id="preview" width="512" height="384">Sorry, your browser does not support Canvas.</canvas><br>
<table>
<tr><td>Sky:</td><td>
<input id="sky" type="file" accept="image/png" onchange="sky.src = window.URL.createObjectURL(this.files[0])"></input>
</td></tr>
<tr><td>Sky Color:</td><td>
<input id="skyColor" type="color" onchange="skyColor = this.value; draw()"></input>
</td></tr>
<tr><td>Clouds:</td><td>
<input id="clouds" type="file" accept="image/png" onchange="clouds.src = window.URL.createObjectURL(this.files[0])"></input>
</td></tr>
<tr><td>Horizont:</td><td>
<input id="horizont" type="file" accept="image/png" onchange="horizont.src = window.URL.createObjectURL(this.files[0])"></input>
</td></tr>
<tr><td>Land:</td><td>
<input id="land" type="file" accept="image/png" onchange="land.src = window.URL.createObjectURL(this.files[0])"></input>
</td></tr>
<tr><td>Border:</td><td>
<input id="border" type="file" accept="image/png" onchange="border.src = window.URL.createObjectURL(this.files[0])"></input>
</td></tr>
<tr><td>Water:</td><td>
<input id="water" type="file" accept="image/png" onchange="water.src = window.URL.createObjectURL(this.files[0])"></input>
</td></tr>
<tr><td>Water Top Color:</td><td>
<input id="waterTopColor" type="color" onchange="waterTopColor = this.value; draw()"></input>
</td></tr>
<tr><td>Water Bottom Color:</td><td>
<input id="waterBottomColor" type="color" onchange="waterBottomColor = this.value; draw()"></input>
</td></tr>
</table>
</body>
</html>