February 17Feb 17 Administrators HTML Canvas Graphics Your browser does not support the <canvas> element. The HTML <canvas> element is used to draw graphics on a web page. The graphic to the left is created with <canvas>. It shows four elements: a red rectangle, a gradient rectangle, a multicolor rectangle, and a multicolor text. What is HTML Canvas? The HTML <canvas> element is used to draw graphics, on the fly, via JavaScript. The <canvas> element is only a container for graphics. You must use JavaScript to actually draw the graphics. Canvas has several methods for drawing paths, boxes, circles, text, and adding images. Canvas is supported by all major browsers. Canvas Examples A canvas is a rectangular area on an HTML page. By default, a canvas has no border and no content. The markup looks like this: <canvas id="myCanvas" width="200" height="100"></canvas> Note: Always specify an id attribute (to be referred to in a script), and a width and height attribute to define the size of the canvas. To add a border, use the style attribute. Here is an example of a basic, empty canvas: Your browser does not support the canvas element. Example <canvas id="myCanvas" width="200" height="100" style="border:1px solid #000000;"> </canvas> Add a JavaScript After creating the rectangular canvas area, you must add a JavaScript to do the drawing. Here are some examples: Draw a Line Your browser does not support the canvas element Example <script>var c = document.getElementById("myCanvas");var ctx = c.getContext("2d"); ctx.moveTo(0, 0);ctx.lineTo(200, 100); ctx.stroke();</script> Draw a Circle Your browser does not support the canvas element Example <script>var c = document.getElementById("myCanvas");var ctx = c.getContext("2d"); ctx.beginPath();ctx.arc(95, 50, 40, 0, 2 * Math.PI);ctx.stroke(); </script> Draw a Text Your browser does not support the canvas element Example <script>var c = document.getElementById("myCanvas");var ctx = c.getContext("2d"); ctx.font = "30px Arial";ctx.fillText("Hello World", 10, 50); </script> Stroke Text Your browser does not support the canvas element Example <script>var c = document.getElementById("myCanvas");var ctx = c.getContext("2d"); ctx.font = "30px Arial";ctx.strokeText("Hello World", 10, 50); </script> Draw Linear Gradient Your browser does not support the canvas element Example <script>var c = document.getElementById("myCanvas"); var ctx = c.getContext("2d"); // Create gradient var grd = ctx.createLinearGradient(0, 0, 200, 0); grd.addColorStop(0, "red"); grd.addColorStop(1, "white"); // Fill with gradient ctx.fillStyle = grd; ctx.fillRect(10, 10, 150, 80);</script> Draw Circular Gradient Your browser does not support the canvas element Example <script>var c = document.getElementById("myCanvas"); var ctx = c.getContext("2d"); // Create gradient var grd = ctx.createRadialGradient(75, 50, 5, 90, 60, 100); grd.addColorStop(0, "red"); grd.addColorStop(1, "white"); // Fill with gradient ctx.fillStyle = grd;ctx.fillRect(10, 10, 150, 80);</script> Draw Image Example <script>var c = document.getElementById("myCanvas"); var ctx = c.getContext("2d"); var img = document.getElementById("scream"); ctx.drawImage(img, 10, 10);</script> HTML Canvas Tutorial To learn more about <canvas>, please read our HTML Canvas Tutorial.
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