three.js tiletipの切り取り

onload で切り取る。

//...

function tip(num,size){return (tex)=>{
  size=size||16,num=num||0;
  let img=tex.image,w=img.naturalWidth,h=img.naturalHeight
  ,c=document.createElement('canvas'),ctx=c.getContext("2d")
  ,nw=~~(w/size),nh =~~(h/size),x=num%nw,y=~~(num/nw)
  ;
  c.height=c.width=size
  ctx.drawImage(img,x*size,y*size,size,size, 0,0,size,size)
  tex.image.src=c.toDataURL()
  tex.needsUpdate=true////
 }
}

//var loader=new THREE.TextureLoader()
//let tex=loader.load(url,tip(number,size))