How to extract sprites from a spritesheet with pure javascript-CodePudding

So I have this spritesheet with all of the different tiles from legends of zelda is there a way in which I could get enter in a function like getTile(2,1) and it would return the base64 encoding for the knight?

So far I have tried this

function getTiles() {
  var sprites = new Image();
  sprites.src = 'https://cdn.glitch.me/b3505ee1-a321-48ea-baf5-d84841324af1/d3b13ce6-f5ed-4122-9bd9-37f74d13d470.image.png?v=1634242985542';

  allOverworldTiles = []

  var i = 0;
  for (var top = 0; top < 8 * 17; top  = 17) {
    for (var left = 0; left < 20 * 17; left  = 17) {
      var canvas = document.createElement("canvas");
      var ctx = canvas.getContext("2d");
      canvas.width = 16;
      canvas.height = 16;
      ctx.drawImage(sprites, left   1, top   1, 16, 16, 0, 0, 16, 16)
    }
  }
  var dataURL = canvas.toDataURL("image/png");
  var newTab = window.open('about:blank', 'image from canvas');
  newTab.document.write("<img src='"   dataURL   "' alt='from canvas'/>");
}

I would prefer if the answer was in vanilla javascript

CodePudding user response：

Some issues on your code...

you need an onl oad event to make sure the image has loaded before you can do anything
you need sprites.crossOrigin="anonymous" or you will get a Tainted canvas error
your logic was not clear, you had a double loop but only one toDataURL outside the loop

Here is a working prototype

var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = canvas.height = 16;

var sprites = new Image();
sprites.crossOrigin="anonymous"
sprites.src = 'https://cdn.glitch.me/b3505ee1-a321-48ea-baf5-d84841324af1/d3b13ce6-f5ed-4122-9bd9-37f74d13d470.image.png?v=1634242985542';
sprites.onload = getTiles

function getTile(x, y) {
  ctx.drawImage(sprites, x * 17   1, y * 17   1, 16, 16, 0, 0, 16, 16)
  return canvas.toDataURL("image/png");
}

function getTiles() {
  var knight1 = getTile(2, 1)
  document.write("<img src='"   knight1   "'/>");
  
  var knight2 = getTile(8, 1)
  document.write("<img src='"   knight2   "'/>");
  
  var knight3 = getTile(14, 1)
  document.write("<img src='"   knight3   "'/>");
}