What are save and restore methods in HTML5 Canvas?

JavascriptWeb DevelopmentFront End Scripts

HTML5 canvas provides two important methods to save and restore the canvas states. Canvas states are stored on a stack every time the save method is called, and the last saved state is returned from the stack every time the restore method is called.

Sr.No.
Method and Description
1
save()
This method pushes the current state onto the stack.
2
restore()
This method pops the top state on the stack, restoring the context to that state.

Example

You can try to run the following code learn about save and restore methods in Canvas:

<!DOCTYPE HTML>
<html>
   <head>
      <style>
         #test {
            width: 100px;
            height:100px;
            margin: 0px auto;
         }
      </style>
      <script>
         function drawShape(){

            // get the canvas element using the DOM
            var canvas = document.getElementById('mycanvas');

            // Make sure we don't execute when canvas isn't supported
            if (canvas.getContext){

               // use getContext to use the canvas for drawing
               var ctx = canvas.getContext('2d');

               // draw a rectangle with default settings
               ctx.fillRect(0,0,150,150);

               // Save the default state
               ctx.save();

               // Make changes to the settings
               ctx.fillStyle = '#66FFFF'
               ctx.fillRect( 15,15,120,120);

               // Save the current state
               ctx.save();

               // Make the new changes to the settings
               ctx.fillStyle = '#993333'
               ctx.globalAlpha = 0.5;
               ctx.fillRect(30,30,90,90);

               // Restore previous state
               ctx.restore();

               // Draw a rectangle with restored settings
               ctx.fillRect(45,45,60,60);

               // Restore original state
               ctx.restore();

               // Draw a rectangle with restored settings
               ctx.fillRect(40,40,90,90);
            } else {
               alert('You need Safari or Firefox 1.5+ to see this demo.');
            }
         }
      </script>
   </head>
   <body id = "test" onload = "drawShape();">
      <canvas id = "mycanvas"></canvas>
   </body>
</html>
raja
Published on 10-Apr-2018 13:33:29
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