Context in canvas

HTMLCanvasElement.getContext()

You can access a element with the HTML DOM method getElementById(). To draw in the canvas you need to create a 2D context object. For example:. Initially, the canvas is blank. To draw something, you need to access the rendering context and use it to draw on the canvas. The getContext takes one argument which is the type of context. For example, you use the "2d" to get a 2D rendering context object, which is an instance of the CanvasRenderingContext2D interface. The following example shows how to select the canvas element using the querySelector method and access the drawing context by calling its getContext method:. To do it, you use the following code:. The 2D drawing context features methods for drawing simple 2D shapes such as paths, rectangles, and arcs. All coordinate values are calculated in relation to the 0,0 with x increasing to the right and y increasing to the bottom.

• 📋HTMLCanvasElement.getContext()
• 📋What is getContext in HTML5 Canvas?
• 📋JavaScript Canvas

JavaScript Canvas

The Canvas API allows JavaScript to draw graphics on the canvas. The Canvas API can draw shapes, lines, curves, boxes, text, and images, with colors, rotations, transparencies, and . At the end of this page, you will know how to set up a canvas 2D context and have drawn a first example in your browser. These are both optional and can also be set using DOM properties. When no width and height attributes are specified, the canvas will initially be pixels wide and pixels high. The element can be sized arbitrarily by CSS , but during rendering the image is scaled to fit its layout size: if the CSS sizing doesn't respect the ratio of the initial canvas, it will appear distorted. It is always a good idea to supply an id because this makes it much easier to identify it in a script. These rules, however, don't affect the actual drawing on the canvas. We'll see how this is done in a dedicated chapter of this tutorial. When no styling rules are applied to the canvas it will initially be fully transparent. You should always provide fallback content, captions, and alternative text, as appropriate for the media type.

The CanvasRenderingContext2D interface, part of the Canvas API, provides the 2D rendering context for the drawing surface of a element. It is used for drawing . The HTMLCanvasElement. Later calls to this method on the same canvas element, with the same contextType argument, will always return the same drawing context instance as was returned the first time the method was invoked. It is not possible to get a different drawing context object on a given canvas element. A string containing the context identifier defining the drawing context associated to the canvas. Possible values are:. Creates a CanvasRenderingContext2D object representing a two-dimensional rendering context. Creates a WebGLRenderingContext object representing a three-dimensional rendering context. This context is only available on browsers that implement WebGL version 1 OpenGL ES 2. Creates a WebGL2RenderingContext object representing a three-dimensional rendering context.

What is getContext in HTML5 Canvas?

context = canvas. getContext (contextId [, ]) Returns an object that exposes an API for drawing on the canvas. The first argument specifies the desired API. Subsequent . The canvas element provides scripts with a resolution-dependent bitmap canvas, which can be used for rendering graphs, game graphics, or other visual images on the fly. Authors should not use the canvas element in a document when a more suitable element is available. For example, it is inappropriate to use a canvas element to render a page heading: if the desired presentation of the heading is graphically intense, it should be marked up using appropriate elements typically h1 and then styled using CSS and supporting technologies such as XBL. When authors use the canvas element, they must also provide content that, when presented to the user, conveys essentially the same function or purpose as the bitmap canvas. This content may be placed as content of the canvas element. The contents of the canvas element, if any, are the element's fallback content. In interactive visual media, if scripting is enabled for the canvas element, and if support for canvas elements has been enabled, the canvas element represents embedded content consisting of a dynamically created image. In non-interactive, static, visual media, if the canvas element has been previously painted on e. Otherwise, the element represents its fallback content instead. In non-visual media, and in visual media if scripting is disabled for the canvas element or if support for canvas elements has been disabled, the canvas element represents its fallback content instead.

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HTMLCanvasElement: getContext() method

The text() method returns a drawing context on the canvas, or null if the context identifier is not supported. Syntax text. .

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Mehr erfahren In context with meaning: If something is seen in context or if it is put into context, it is considered together with all the factors that relate to it. Taxation is not popular in principle, merely acceptable in context. See .