Tracing back the tainted canvas glitch in MDN's demonstration and resolving it

I am currently working my way through the Canvas tutorial on MDN.

Everything was going smoothly until I reached the Pixel manipulation, specifically a color picker example.

However, when using getImageData, I encountered this error:

MDNTutorialBaseppp.html:21 Uncaught DOMException: Failed to execute 'getImageData' on 'CanvasRenderingContext2D': The canvas has been tainted by cross-origin data. at HTMLCanvasElement.pick

Below is the code that I have been running:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8"/>
  </head>
  <body>
    <canvas id="canvas" width="600" height="300"></canvas>
    <script>
      var img = new Image();
      //img.src = 'https://mdn.mozillademos.org/files/5397/rhino.jpg';
      img.src = 'photo2.jpg';
      var canvas = document.getElementById('canvas');
      var ctx = canvas.getContext('2d');
      img.onload = function() {
        ctx.drawImage(img, 0, 0);
        img.style.display = 'none';
      };
      var color = document.getElementById('color');
      function pick(event) {
        var x = event.layerX;
        var y = event.layerY;
        var pixel = ctx.getImageData(x, y, 1, 1);
        var data = pixel.data;
        var rgba = 'rgba(' + data[0] + ', ' + data[1] +
            ', ' + data[2] + ', ' + (data[3] / 255) + ')';
        color.style.background =  rgba;
        color.textContent = rgba;
      }
      canvas.addEventListener('mousemove', pick);
    </script>
  </body>
</html>

I've been stuck on this issue for hours and haven't been able to figure out what's wrong. Can anyone help identify where I'm going wrong?

Answer №1

The advice given in the responses to this inquiry offers a strategy for addressing the specific situation at hand. Setting up a local server is crucial, but thankfully it's not too difficult. The core problem being discussed is a complex subject that I am still trying to grasp fully.

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