HTML5 Game - Turn image to Grayscale

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  2. HTML5 Game
  3. Canvas
  4. Image Data

Description

Turn image to Grayscale

Demo

ResultView the demo in separate window 

<!DOCTYPE html>

<html>
  <head>
    <title>Manipulating images and video</title>
    <meta charset="utf-8">
    //from  w w  w.  ja va2s. c  o m
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
    
    <script type="text/javascript">
      $(document).ready(function() {  
        let canvas = $("#myCanvas");
        let context = canvas.get(0).getContext("2d");
        
        // Grayscale
        let image = new Image();
        image.src = "http://java2s.com/style/download.png";
        $(image).load(function() {
          context.drawImage(image, 0, 0, 1024, 683, 0, 0, 500, 500);
          
          let imageData = context.getImageData(0, 0, canvas.width(), canvas.height());
          let pixels = imageData.data;
          let numPixels = pixels.length;
          
          // Clear the image
          context.clearRect(0, 0, canvas.width(), canvas.height());
        
          // Access and change pixel values
          for (let i = 0; i < numPixels; i++) {
            let average = (pixels[i*4]+pixels[i*4+1]+pixels[i*4+2])/3;
            pixels[i*4] = average; // Red
            pixels[i*4+1] = average; // Green
            pixels[i*4+2] = average; // Blue
          };
          
          // Draw image data to the canvas
          context.putImageData(imageData, 0, 0);
        });
      
      });
    </script>
  </head>
  
  <body>
    <canvas id="myCanvas" width="500" height="500">
      <!-- Insert fallback content here -->
    </canvas>
  </body>
</html>

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