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+---
+title: HTMLCanvasElement.getContext()
+slug: Web/API/HTMLCanvasElement/getContext
+tags:
+  - TV
+translation_of: Web/API/HTMLCanvasElement/getContext
+---
+<div>{{APIRef("Canvas API")}}</div>
+
+<p><span class="seoSummary">The <strong><code>HTMLCanvasElement.getContext()</code></strong> method returns a drawing context on the canvas, or {{jsxref("null")}} if the context identifier is not supported.</span></p>
+
+<p>Later calls to this method on the same canvas element return the same drawing context instance as was returned the last time the method was invoked with the same <code>contextType</code> argument. To get a different drawing context object you need to pass a different <code>contextType</code> or call the method on a different canvas element. </p>
+
+<h2 id="Syntax">Syntax</h2>
+
+<pre class="syntaxbox">var <em>ctx</em> = <em>canvas</em>.getContext(<em>contextType</em>);
+var <em>ctx</em> = <em>canvas</em>.getContext(<em>contextType</em>, <em>contextAttributes</em>);
+</pre>
+
+<h3 id="Parameters">Parameters</h3>
+
+<dl>
+ <dt><code>contextType</code></dt>
+ <dd>Is a {{domxref("DOMString")}} containing the context identifier defining the drawing context associated to the canvas. Possible values are:
+ <ul>
+  <li><code>"2d"</code>, leading to the creation of a {{domxref("CanvasRenderingContext2D")}} object representing a two-dimensional rendering context.</li>
+  <li><code>"webgl"</code> (or <code>"experimental-webgl"</code>) which will create a {{domxref("WebGLRenderingContext")}} object representing a three-dimensional rendering context. This context is only available on browsers that implement <a href="https://developer.mozilla.org/en-US/docs/Web/WebGL">WebGL</a> version 1 (OpenGL ES 2.0).</li>
+  <li><code>"webgl2"</code> which will create a {{domxref("WebGL2RenderingContext")}} object representing a three-dimensional rendering context. This context is only available on browsers that implement <a href="https://developer.mozilla.org/en-US/docs/Web/WebGL">WebGL</a> version 2 (OpenGL ES 3.0). {{experimental_inline}}</li>
+  <li><code>"bitmaprenderer"</code> which will create an {{domxref("ImageBitmapRenderingContext")}} which only provides functionality to replace the content of the canvas with a given {{domxref("ImageBitmap")}}.</li>
+ </ul>
+
+ <div class="note">
+ <p><strong>Note</strong>: The identifier <code>"experimental-webgl"</code> is used in new implementations of WebGL. These implementations have either not reached test suite conformance, or the graphics drivers on the platform are not yet stable. The <a href="https://www.khronos.org/">Khronos Group</a> certifies WebGL implementations under certain <a href="https://www.khronos.org/registry/webgl/sdk/tests/CONFORMANCE_RULES.txt">conformance rules</a>.</p>
+ </div>
+ </dd>
+ <dt><code>contextAttributes</code></dt>
+ <dd>
+ <p>You can use several context attributes when creating your rendering context, for example:</p>
+
+ <pre class="brush: js">const gl = canvas.getContext('webgl', {
+  antialias: false,
+  depth: false
+});</pre>
+ 2d context attributes:
+
+ <ul>
+  <li><strong><code>alpha</code></strong>: Boolean that indicates if the canvas contains an alpha channel. If set to <code>false</code>, the browser now knows that the backdrop is always opaque, which can speed up drawing of transparent content and images.</li>
+  <li>{{non-standard_inline}} (Gecko only) <strong><code>willReadFrequently</code></strong>: Boolean that indicates whether or not a lot of read-back operations are planned. This will force the use of a software (instead of hardware accelerated) 2D canvas and can save memory when calling {{domxref("CanvasRenderingContext2D.getImageData", "getImageData()")}} frequently. This option is only available, if the flag <code>gfx.canvas.willReadFrequently.enable</code> is set to <code>true</code> (which, by default, is only the case for B2G/Firefox OS).</li>
+  <li>{{non-standard_inline}} (Blink only) <strong><code>storage</code></strong>: String that indicates which storage is used ("persistent" by default).</li>
+ </ul>
+ WebGL context attributes:
+
+ <ul>
+  <li><strong><code>alpha</code></strong>: Boolean that indicates if the canvas contains an alpha buffer.</li>
+  <li><strong><code>antialias</code></strong>: Boolean that indicates whether or not to perform anti-aliasing.</li>
+  <li><strong><code>depth</code></strong>: Boolean that indicates that the drawing buffer has a depth buffer of at least 16 bits.</li>
+  <li><code><strong>failIfMajorPerformanceCaveat</strong></code>: Boolean that indicates if a context will be created if the system performance is low.</li>
+  <li><code><strong>powerPreference</strong></code>: A hint to the user agent indicating what configuration of GPU is suitable for the WebGL context. Possible values are:
+   <ul>
+    <li><code>"default"</code>: Let the user agent decide which GPU configuration is most suitable. This is the default value.</li>
+    <li><code>"high-performance"</code>: Prioritizes rendering performance over power consumption.</li>
+    <li><code>"low-power"</code>: Prioritizes power saving over rendering performance.</li>
+   </ul>
+  </li>
+  <li><strong><code>premultipliedAlpha</code></strong>: Boolean that indicates that the page compositor will assume the drawing buffer contains colors with pre-multiplied alpha.</li>
+  <li><strong><code>preserveDrawingBuffer</code></strong>: If the value is true the buffers will not be cleared and will preserve their values until cleared or overwritten by the author.</li>
+  <li><strong><code>stencil</code></strong>: Boolean that indicates that the drawing buffer has a stencil buffer of at least 8 bits.</li>
+ </ul>
+ </dd>
+</dl>
+
+<h3 id="Return_value">Return value</h3>
+
+<p>A {{domxref("RenderingContext")}} which is either a</p>
+
+<ul>
+ <li>{{domxref("CanvasRenderingContext2D")}} for <code>"2d"</code>,</li>
+ <li>{{domxref("WebGLRenderingContext")}} for <code>"webgl"</code> and <code>"experimental-webgl"</code>,</li>
+ <li>{{domxref("WebGL2RenderingContext")}} for <code>"webgl2"</code> or</li>
+ <li>{{domxref("ImageBitmapRenderingContext")}} for <code>"bitmaprenderer"</code>.</li>
+</ul>
+
+<p>If the <code>contextType</code> doesn't match a possible drawing context, <code>null</code> is returned.</p>
+
+<h2 id="Examples">Examples</h2>
+
+<p>Given this {{HTMLElement("canvas")}} element:</p>
+
+<pre class="brush: html">&lt;canvas id="canvas" width="300" height="300"&gt;&lt;/canvas&gt;
+</pre>
+
+<p>You can get a <code>2d</code> context of the canvas with the following code:</p>
+
+<pre class="brush: js">var canvas = document.getElementById('canvas');
+var ctx = canvas.getContext('2d');
+console.log(ctx); // CanvasRenderingContext2D { ... }
+</pre>
+
+<p>Now you have the <a href="/en-US/docs/Web/API/CanvasRenderingContext2D">2D rendering context</a> for a canvas and you can draw within it.</p>
+
+<h2 id="Specifications">Specifications</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">Specification</th>
+   <th scope="col">Status</th>
+   <th scope="col">Comment</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('HTML WHATWG', "scripting.html#dom-canvas-getcontext", "HTMLCanvasElement.getContext")}}</td>
+   <td>{{Spec2('HTML WHATWG')}}</td>
+   <td>No change since the latest snapshot, {{SpecName('HTML5 W3C')}}</td>
+  </tr>
+  <tr>
+   <td>{{SpecName('HTML5.1', "semantics-scripting.html#dom-htmlcanvaselement-getcontext", "HTMLCanvasElement.getContext")}}</td>
+   <td>{{Spec2('HTML5.1')}}</td>
+   <td></td>
+  </tr>
+  <tr>
+   <td>{{SpecName('HTML5 W3C', "scripting-1.html#dom-canvas-getcontext", "HTMLCanvasElement.getContext")}}</td>
+   <td>{{Spec2('HTML5 W3C')}}</td>
+   <td>Snapshot of the {{SpecName('HTML WHATWG')}} containing the initial definition.</td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="Browser_compatibility">Browser compatibility</h2>
+
+
+
+<p>{{Compat("api.HTMLCanvasElement.getContext")}}</p>
+
+<h2 id="See_also">See also</h2>
+
+<ul>
+ <li>The interface defining it, {{domxref("HTMLCanvasElement")}}.</li>
+ <li>{{domxref("OffscreenCanvas.getContext()")}}</li>
+ <li>Available rendering contexts: {{domxref("CanvasRenderingContext2D")}}, {{domxref("WebGLRenderingContext")}} and {{domxref("WebGL2RenderingContext")}} and {{domxref("ImageBitmapRenderingContext")}}.</li>
+</ul>
diff --git a/files/vi/web/api/htmlcanvaselement/index.html b/files/vi/web/api/htmlcanvaselement/index.html
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index 0000000000..50b2592322
--- /dev/null
+++ b/files/vi/web/api/htmlcanvaselement/index.html
@@ -0,0 +1,114 @@
+---
+title: HTMLCanvasElement
+slug: Web/API/HTMLCanvasElement
+tags:
+  - API
+  - Canvas
+  - HTML DOM
+  - Interface
+  - NeedsTranslation
+  - Reference
+  - TopicStub
+translation_of: Web/API/HTMLCanvasElement
+---
+<div>
+<div>{{APIRef("Canvas API")}}</div>
+</div>
+
+<p>The <strong><code>HTMLCanvasElement</code></strong> interface provides properties and methods for manipulating the layout and presentation of {{HtmlElement("canvas")}} elements. The <code>HTMLCanvasElement</code> interface also inherits the properties and methods of the {{domxref("HTMLElement")}} interface.</p>
+
+<p>{{InheritanceDiagram(600, 120)}}</p>
+
+<h2 id="Properties">Properties</h2>
+
+<p><em>Inherits properties from its parent, </em><em>{{domxref("HTMLElement")}}.</em></p>
+
+<dl>
+ <dt>{{domxref("HTMLCanvasElement.height")}}</dt>
+ <dd>Is a positive <code>integer</code> reflecting the {{htmlattrxref("height", "canvas")}} HTML attribute of the {{HTMLElement("canvas")}} element interpreted in CSS pixels. When the attribute is not specified, or if it is set to an invalid value, like a negative, the default value of <code>150</code> is used.</dd>
+ <dt>{{domxref("HTMLCanvasElement.width")}}</dt>
+ <dd>Is a positive <code>integer</code> reflecting the {{htmlattrxref("width", "canvas")}} HTML attribute of the {{HTMLElement("canvas")}} element interpreted in CSS pixels. When the attribute is not specified, or if it is set to an invalid value, like a negative, the default value of <code>300</code> is used.</dd>
+ <dt>{{domxref("HTMLCanvasElement.mozOpaque")}} {{non-standard_inline}} {{deprecated_inline}}</dt>
+ <dd>Is a {{jsxref("Boolean")}} reflecting the {{htmlattrxref("moz-opaque", "canvas")}} HTML attribute of the {{HTMLElement("canvas")}} element. It lets the canvas know whether or not translucency will be a factor. If the canvas knows there's no translucency, painting performance can be optimized. This is only supported in Mozilla-based browsers; use the standardized {{domxref("HTMLCanvasElement.getContext()", "canvas.getContext('2d', { alpha: false })")}} instead.</dd>
+ <dt>{{domxref("HTMLCanvasElement.mozPrintCallback")}}{{non-standard_inline}}</dt>
+ <dd>Is a <code>function</code> that is Initially null. Web content can set this to a JavaScript function that will be called when the canvas is to be redrawn while the page is being printed. When called, the callback is passed a "printState" object that implements the <a href="https://searchfox.org/mozilla-central/search?q=interface MozCanvasPrintState&amp;path=HTMLCanvasElement.webidl">MozCanvasPrintState</a> interface. The callback can get the context to draw to from the printState object and must then call done() on it when finished. The purpose of <code>mozPrintCallback</code> is to obtain a higher resolution rendering of the canvas at the resolution of the printer being used. <a href="https://blog.mozilla.org/labs/2012/09/a-new-way-to-control-printing-output/">See this blog post.</a></dd>
+</dl>
+
+<h2 id="Methods">Methods</h2>
+
+<p><em>Inherits methods from its parent, </em><em>{{domxref("HTMLElement")}}.</em></p>
+
+<dl>
+ <dt>{{domxref("HTMLCanvasElement.captureStream()")}} {{experimental_inline}}</dt>
+ <dd>Returns a {{domxref("CanvasCaptureMediaStream")}} that is a real-time video capture of the surface of the canvas.</dd>
+ <dt>{{domxref("HTMLCanvasElement.getContext()")}}</dt>
+ <dd>Returns a drawing context on the canvas, or null if the context ID is not supported. A drawing context lets you draw on the canvas. Calling getContext with <code>"2d"</code> returns a {{domxref("CanvasRenderingContext2D")}} object, whereas calling it with <code>"webgl"</code> (or <code>"experimental-webgl"</code>) returns a {{domxref("WebGLRenderingContext")}} object. This context is only available on browsers that implement <a href="/en-US/docs/Web/WebGL">WebGL</a>.</dd>
+ <dt>{{domxref("HTMLCanvasElement.toDataURL()")}}</dt>
+ <dd>Returns a data-URL containing a representation of the image in the format specified by the <code>type</code> parameter (defaults to <code>png</code>). The returned image is in a resolution of 96dpi.</dd>
+ <dt>{{domxref("HTMLCanvasElement.toBlob()")}}</dt>
+ <dd>Creates a {{domxref("Blob")}} object representing the image contained in the canvas; this file may be cached on the disk or stored in memory at the discretion of the user agent.</dd>
+ <dt>{{domxref("HTMLCanvasElement.transferControlToOffscreen()")}} {{experimental_inline}}</dt>
+ <dd>Transfers control to an {{domxref("OffscreenCanvas")}} object, either on the main thread or on a worker.</dd>
+ <dt>{{domxref("HTMLCanvasElement.mozGetAsFile()")}} {{non-standard_inline}} {{deprecated_inline}}</dt>
+ <dd>Returns a {{domxref("File")}} object representing the image contained in the canvas; this file is a memory-based file, with the specified <code>name</code>. If <code>type</code> is not specified, the image type is <code>image/png</code>.</dd>
+</dl>
+
+<h2 id="Events">Events</h2>
+
+<p>Listen to these events using <code><a href="/en-US/docs/Web/API/EventTarget/addEventListener">addEventListener()</a></code>.</p>
+
+<dl>
+ <dt><code><a href="/en-US/docs/Web/API/HTMLCanvasElement/webglcontextcreationerror_event">webglcontextcreationerror</a></code></dt>
+ <dd>Fired if the user agent is unable to create a <code>WebGLRenderingContext</code> or <code>WebGL2RenderingContext</code> context.</dd>
+ <dt><code><a href="/en-US/docs/Web/API/HTMLCanvasElement/webglcontextlost_event">webglcontextlost</a></code></dt>
+ <dd>Fired if the user agent detects that the drawing buffer associated with a <code>WebGLRenderingContext</code> or <code>WebGL2RenderingContext</code> object has been lost.</dd>
+ <dt><code><a href="/en-US/docs/Web/API/HTMLCanvasElement/webglcontextrestored_event">webglcontextrestored</a></code></dt>
+ <dd>Fired if the user agent restores the drawing buffer for a <code>WebGLRenderingContext</code> or <code>WebGL2RenderingContext</code> object.</dd>
+</dl>
+
+<h2 id="Specifications">Specifications</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">Specification</th>
+   <th scope="col">Status</th>
+   <th scope="col">Comment</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('Media Capture DOM Elements', '#html-media-element-media-capture-extensions', 'HTMLCanvasElement')}}</td>
+   <td>{{Spec2('Media Capture DOM Elements')}}</td>
+   <td>Adds the method <code>captureStream()</code>.</td>
+  </tr>
+  <tr>
+   <td>{{SpecName('HTML WHATWG', "#htmlcanvaselement", "HTMLCanvasElement")}}</td>
+   <td>{{Spec2('HTML WHATWG')}}</td>
+   <td>The method <code>getContext()</code> now returns a {{domxref("RenderingContext")}} rather than an opaque <code>object</code>.<br>
+    The <code>transferControlToOffscreen()</code>method has been added.</td>
+  </tr>
+  <tr>
+   <td>{{SpecName('HTML5.1', "scripting-1.html#the-canvas-element", "HTMLCanvasElement")}}</td>
+   <td>{{Spec2('HTML5.1')}}</td>
+   <td> </td>
+  </tr>
+  <tr>
+   <td>{{SpecName('HTML5 W3C', "scripting-1.html#the-canvas-element", "HTMLCanvasElement")}}</td>
+   <td>{{Spec2('HTML5 W3C')}}</td>
+   <td>Initial definition.</td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="Browser_compatibility">Browser compatibility</h2>
+
+<div>
+
+
+<p>{{Compat("api.HTMLCanvasElement")}}</p>
+</div>
+
+<h2 id="See_also">See also</h2>
+
+<ul>
+ <li>HTML element implementing this interface: {{HTMLElement("canvas")}}</li>
+</ul>