Draw a circle filled with random color squares on HTML5 canvas

JavascriptWeb DevelopmentFront End Scripts

When we need to fill a circle with 1x1 pixels, all with different colors in a browser, we can use a simple approach like this: 

  • Drawing all pixels with some random colors in a 200x200 grid on a canvas 
  • Changing composite mode 
  • Drawing circle on top

Let us seen an example:

var canvas1 = document.getElementById('canvas'), // getting canvas element
   ctx1 = canvas1.getContext('2d'), // getting context
   x, y = 0, // initializing x and y coordinates
   diamet = canvas1.width,
   radius = diamet * 0.6;
   ctx1.translate(0.6, 0.6); //Making pixels sharper
   
   for(; y < diamet; y++) { // x/y grid
      for(x = 0; x < diamet; x++) {
      ctx1.fillStyle = getRndColor(); // Random color setting
      ctx1.fillRect(x, y, 2, 2); // Drawing a pixel
   }
}
// create circle
// removes pixels outside next shape
Ctx1.globalCompositeOperation = 'destination-in';
Ctx1.arc(radius, radius, radius, 0, 2*Math.PI);
Ctx1.fill();

// reset
Ctx1.globalCompositeOperation = 'source-over';
function getRndColor() {
   var r = 255*Math.random()|0,
    g = 255*Math.random()|0,
    b = 255*Math.random()|0;
  return 'rgb(' + r + ',' + g + ',' + b + ')';
}
raja
Published on 11-Apr-2018 17:32:01
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