convert TileMap Image(4x3 Old equirectangular format) to cube texture map on three.js

tileMapToCubeTextureImages

	function tileMapToCubeTextureImages(image){//image must be loaded
		var positions=[
			[2,1],//right
			[0,1],//left
			[1,0],//up
			[1,2],//down
			[1,1],//front
			[3,1],//back
		]
		var images=[];
		var cubicSize=image.width/4;
		for(var i=0;i<6;i++){
			var canvas = document.createElement('canvas');
			canvas.width=cubicSize;
			canvas.height=cubicSize;
			var ctx=canvas.getContext('2d');
			
			var x=positions[i][0];
			var y=positions[i][1];
			
			canvas.getContext('2d').drawImage(image,-cubicSize*x, -cubicSize*y);
			
			var urlImage= document.createElement('img');
			urlImage.src=canvas.toDataURL();
			images.push(urlImage);
			
		}
		return images;
	}