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How to Create Background Like TV Noise in a Canvas ?

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TV noise is a random black-and-white dot pixel pattern displayed when no transmission signal is obtained by the receiver antenna of television sets or other such devices. To create that scenario as a background we will need HTML, CSS, and JavaScript. HTML is used to create the canvas area or you can use the whole background as an area. CSS will be applicable for designing the background and JavaScript will create the TV noise animation. We will accomplish that in stepwise. The below steps are mentioned and described one by one.

How to Create Background Like TV Noise in a Canvas ?

Example:

html

<!DOCTYPE html>
<html lang="en">
  
<head>
    <meta charset="utf-8">
    <title>TV noise Background</title>
</head>
  
<body>
    <canvas id="canvas"></canvas>
    <h1>GeeksforGeeks</h1>
    <h2>A Computer Science Portal for Geeks</h2>
    <h3>Animated TV noise Background</h3>
</body>
  
</html>

                    

CSS

<style> 
    #canvas {
        z-index: -100;
        position: absolute;
        top: 0;
        left: 0;
        opacity: 0.8;
        background-color: #fff;
    }
    h1 {
        color: green;
        font-size: 50px;
        margin-bottom: 0;
    }
    body {
        text-align: center;
    }
</style>

                    

Javascript

<script>
    var canvas = document.getElementById('canvas'),
               
    /* The getContext() method returns an object 
    that provides methods and properties for 
    drawing on the canvas. */
    ctx = canvas.getContext('2d');
   
    /* Setting canvas width and height equal to
    window screen width and height. */
    function resize() {
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
    }
    resize();
    window.onresize = resize;
   
    // Function to generate noise effect
    function generate_noise(ctx) {
        var w = ctx.canvas.width,
        h = ctx.canvas.height,
                   
        /* This creates a new ImageData object
        with the specified dimensions(i.e canvas
        width and height). All pixels are set to
        transparent black (i.e rgba(0,0,0,0)). */
        idata = ctx.createImageData(w, h), 
                   
        // Creating Uint32Array typed array
        buffer32 = new Uint32Array(idata.data.buffer), 
        buffer_len = buffer32.length,
        i = 0
          
        for ( ; i < buffer_len; i++)
            buffer32[i] = 
                ((255 * Math.random()) | 0) << 24;
               
        /* The putImageData() method puts the image
        data (from a specified ImageData object)
        back onto the canvas. */
        ctx.putImageData(idata, 0, 0); 
    }
   
    // Creating animation effect
    var toggle = true;
    (function loop() {
        toggle = !toggle;
        if (toggle) {
               
            // Loop function is called each time
            // before next repaint.
            requestAnimationFrame(loop); 
            return;
        }
    generate_noise(ctx);
    requestAnimationFrame(loop);
    })();
</script>

                    

Output: Click here to see the live output
 

How to Create Background Like TV Noise in a Canvas ?



Last Updated : 25 Jan, 2023
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