Sprite sheet script.

gistfile1.js

var canvas = document.createElement( 'canvas' );
canvas.width = 2048;
canvas.height = 2048;

canvas.addEventListener( 'click', function() {

	window.open( canvas.toDataURL( 'image/png' ), 'mywindow' );

}, false );

var context = canvas.getContext( '2d' );

/*
context.fillStyle = 'rgb(255,0,0)';
context.fillRect( 0, 0, canvas.width, canvas.height );
*/

document.body.appendChild( canvas );

for ( var i = 0, j = 0; i <= 62; i++, j += 2) {

	loadBitmap( i + 0, 'tree_front/tree_front_lighter' + pad( j, 4 ) + '.png' );

}

function pad( value, amount ) {

	var string = value.toString();

	while ( string.length < amount ) {

		string = '0' + string;

	}

	return string;

}

function loadBitmap( id, path ) {

	var bitmap = document.createElement( 'img' );
	bitmap.addEventListener( 'load', function () {

		var x = ( id * 256 ) % canvas.width;
		var y = Math.floor( ( id * 256 ) / canvas.width ) * 256;

		context.drawImage( this, x, y );

	}, false );
	bitmap.src = path;
	return bitmap;

}