canvas color picker

CanvasRenderingContext2D.getImageData() returns an ImageData object, which is used to describe the pixel data hidden in the canvas area. This area is represented by a rectangle. The starting point is (sx, sy), the width is sw, and the height is sh. Insert picture description here

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    canvas {
     
      cursor: crosshair;}
    div {
     
     width: 200px; height: 100px;}
  </style>
</head>
<body>
  <canvas id="canvas"></canvas>
  <div id="hovered-color"></div>
  <div id="selected-color"></div>
    <script>
      var img = new Image();
      img.crossOrigin = 'anonymous';
      img.src = 'https://imzhangting.github.io/avatar.png';
      var canvas = document.getElementById('canvas');
      var ctx = canvas.getContext('2d');
      canvas.width = 400
      canvas.height = 300
      img.onload = function() {
     
     
        ctx.drawImage(img, 0, 0);
        img.style.display = 'none';
      };
      var hoveredColor = document.getElementById('hovered-color');
      var selectedColor = document.getElementById('selected-color');


      function pick(event, destination) {
     
     
        var x = event.layerX;
        var y = event.layerY;
        var pixel = ctx.getImageData(x, y, 1, 1);
        var data = pixel.data;

          const rgba = `rgba(${
       
       data[0]}, ${
       
       data[1]}, ${
       
       data[2]}, ${
       
       data[3] / 255})`;
          destination.style.background = rgba;
          destination.textContent = rgba;

          return rgba;
      }
      canvas.addEventListener('mousemove', function(event) {
     
     
          pick(event, hoveredColor);
      });
      canvas.addEventListener('click', function(event) {
     
     
          pick(event, selectedColor);
      });
    </script>
</body>
</html>

Guess you like