Canvas (elemento HTML): differenze tra le versioni

Versione delle 16:56, 14 mar 2007

Versione delle 16:58, 14 mar 2007

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'''Canvas''' è una estensione dell'[[HTML]]standar standard <!-- that allows for dynamic rendering of [[Scripting language|scriptable]] [[bitmap]] images.

It was initially introduced by [[Apple Computer|Apple]] for use inside their own [[Mac OS X]] [[Webkit]] component, powering applications like [[Dashboard (software)|Dashboard]] widgets and the [[Safari (browser)|Safari]] browser. Later, it was adopted by [[Gecko (layout engine)|Gecko]] browsers (notably [[Mozilla Application Suite|Mozilla]] and [[Mozilla Firefox|Firefox]]) and [[Opera (internet suite)|Opera]]<ref>[http://www.opera.com/docs/changelogs/windows/900/ Opera 9.0 changelog]</ref>, and standardized by the [[Web Hypertext Application Technology Working Group|WHATWG]] on new proposed specifications for next generation web technologies. [[Novell]] manufactures an [[XForms]] processor plugin for [[Internet Explorer]], which also provides support for the canvas element.<ref>[http://lab.cph.novell.com/nxie/ Novell XForms Explorer]</ref> Independent efforts to support the canvas feature on Internet Explorer do not require plugins and are based solely on [[Vector Markup Language|VML]] and [[JavaScript]].<ref>[http://me.eae.net/archive/2005/12/29/canvas-in-ie/ Canvas in IE]</ref> Google has also begun a project to add canvas abilities to Internet Explorer using the same techniques.<ref>[http://excanvas.sourceforge.net/ Google's Canvas in IE project]</ref>

Canvas consists of a drawable region defined in HTML code with ''height'' and ''width'' attributes. [[JavaScript]] code may access the area through a full set of drawing functions similar to other common 2D APIs, thus allowing for dynamically generated graphics. Some anticipated uses of the canvas include building graphs, animations, and image composition.-->

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==Reactions==

At the time of its introduction the canvas element met with mixed reactions from the web standards community. Some complained about Apple's decision to create a new proprietary element instead of supporting the [[Scalable Vector Graphics|SVG]] standard, which still has not achieved broad web acceptance. Some others argued about the logic upon which canvas was conceived: being completely procedural and not having a descriptive counterpart allowed canvas to 'paint', but drawn elements are not identifiable in a [[Document Object Model|DOM]]-like way. Other people raised concerns, not about the proprietary extension per se, but in regard to the proposed syntax for those elements. For example, they consider the absence of a [[namespace]] indication to be undesirable.<ref>[http://ln.hixie.ch/?start=1089635050&count=1 Ian Hickson remarks regarding canvas and other Apple extensions to HTML]</ref>

A web developer unsatisfied by the level of SVG support in Safari has pushed himself to develop an ''SVG Tiny 1.2 to canvas'' [[Rasterisation|rasteriser]] in [[JavaScript]], as a [[proof of concept]] against claims that canvas was a lot easier to implement in Safari than a complete SVG integration.<ref>[http://fuchsia-design.com/CanvaSVG/ canvaSVG Javascript object for rendering SVG documents in canvas]</ref> -->

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==References==

<references/>

==Examples==

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*[http://henrikfalck.com/unrealsoccer/ Unreal Soccer] - [[Soccer]] game that uses canvas

*[http://lsysjs.qwert.ch/ LSys/JS] - Interactive [[L-System]] interpreter using canvas.

*[http://ajax3d.sourceforge.net/ Ajax3d] - A 3d engine and simple game implemented with Canvas.-->

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==See also==

*[[Scalable Vector Graphics|SVG]]

*[[Quartz (graphics layer)]]

*[[Cairo (graphics)]]

*[[WHATWG Compare|Comparison of layout engines (Web Applications 1.0)]]-->

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==External links==

*[http://www.whatwg.org/specs/web-apps/current-work/#scs-dynamic Canvas description in WHATWG Web Applications draft specifications]