HTML5 Canvas - Drawing Lines

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Line Methods

We require the following methods to draw lines on the canvas −

Sr.No. Method and Description
1

beginPath()

This method resets the current path.
2

moveTo(x, y)

This method creates a new subpath with the given point.
3

closePath()

This method marks the current subpath as closed, and starts a new subpath with a point the same as the start and end of the newly closed subpath.
4

fill()

This method fills the subpaths with the current fill style.
5

stroke()

This method strokes the subpaths with the current stroke style.
6

lineTo(x, y)

This method adds the given point to the current subpath, connected to the previous one by a straight line.

Example

Following is a simple example which makes use of the above-mentioned methods to draw a triangle.

<!DOCTYPE HTML>

<html>
   <head>
      
      <style>
         #test {
            width: 100px;
            height:100px;
            margin: 0px auto;
         }
      </style>
      
      <script type = "text/javascript">
         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');
            
               // Filled triangle
               ctx.beginPath();
               ctx.moveTo(25,25);
               ctx.lineTo(105,25);
               ctx.lineTo(25,105);
               ctx.fill();
            
               // Stroked triangle
               ctx.beginPath();
               ctx.moveTo(125,125);
               ctx.lineTo(125,45);
               ctx.lineTo(45,125);
               ctx.closePath();
               ctx.stroke();
            } 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>

The above example would draw following shape −

Line Properties

There are several properties which allow us to style lines.

S.No. Property and Description
1

lineWidth [ = value ]

This property returns the current line width and can be set, to change the line width.
2

lineCap [ = value ]

This property returns the current line cap style and can be set, to change the line cap style. The possible line cap styles are butt, round, and square
3

lineJoin [ = value ]

This property returns the current line join style and can be set, to change the line join style. The possible line join styles are bevel, round, andmiter.
4

miterLimit [ = value ]

This property returns the current miter limit ratio and can be set, to change the miter limit ratio.

Example

Following is a simple example which makes use of lineWidth property to draw lines of different width.

<!DOCTYPE HTML>

<html>
   <head>
      
      <style>
         #test {
            width: 100px;
            height:100px;
            margin: 0px auto;
         }
      </style>
      
      <script type = "text/javascript">
         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');
               
               for (i=0;i<10;i++){
                  ctx.lineWidth = 1+i;
                  ctx.beginPath();
                  ctx.moveTo(5+i*14,5);
                  ctx.lineTo(5+i*14,140);
                  ctx.stroke();
               }
            } 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>

The above example would draw following shape −

html5_canvas.htm
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