This image illustrates the difference between bitmap and vector images. The bitmap image is composed of a fixed set of dots, while the vector image is composed of a fixed set of shapes. In the picture, scaling the bitmap reveals the dots while scaling the vector image preserves the shapes.

Scalable Vector Graphics (SVG) is a family of specifications of an XML-based file format for two-dimensional vector graphics, both static and dynamic (i.e., interactive or animated). The SVG specification is an open standard that has been under development by the World Wide Web Consortium (W3C) since 1999.

SVG images and their behaviors are defined in XML text files. This means that they can be searched, indexed, scripted, and, if need be, compressed. As XML files, SVG images can be created and edited with any text editor, but it is often more convenient to create them with drawing programs such as Inkscape.

All major modern web browsers have at least some degree of support for SVG and can render markup directly, including Mozilla Firefox, Internet Explorer 9, Google Chrome, Opera, and Safari. Earlier versions of Microsoft Internet Explorer (IE) do not support SVG natively.^[3]

Overview[link]

SVG has been in development since 1999 by a group of companies within the W3C after the competing standards Precision Graphics Markup Language (PGML) – developed from Adobe's PostScript – and Vector Markup Language (VML) – developed from Microsoft's RTF – were submitted to W3C in 1998. SVG drew on experience from the designs of both those formats.^[4]

SVG allows three types of graphic objects: vector graphics, raster graphics, and text. Graphical objects, including PNG and JPEG raster images, can be grouped, styled, transformed, and composited into previously rendered objects. SVG does not directly support z-indices^[5] that separate drawing order from document order for overlapping objects, unlike some other vector markup languages like VML. Text can be in any XML namespace suitable to the application, which enhances search ability and accessibility of the SVG graphics. The feature set includes nested transformations, clipping paths, alpha masks, filter effects, template objects, and extensibility.

Since 2001, the SVG specification has been updated to version 1.1 (current Recommendation) and 1.2 (still a Working Draft). The SVG Mobile Recommendation introduced two simplified profiles of SVG 1.1, SVG Basic and SVG Tiny, meant for devices with reduced computational and display capabilities. SVG Tiny later became an autonomous Recommendation (current version 1.2) and the basis for SVG 1.2. In addition to these variants and profiles, the SVG Print specification (still a Working Draft) contains guidelines for printable SVG 1.2 and SVG Tiny 1.2 documents.

Although not directly comparable to SVG since it is a bitmap-based format, the Canvas element in HTML5 provides an approach to rendering dynamic graphics in HTML that is procedural rather than declarative: instead of specifying the shapes to draw in XML, the author executes drawing commands from a script. Canvas does not allow for static rendering, and drawn elements are not identifiable in a DOM-like way.

Printing[link]

Though the SVG Specification primarily focuses on vector graphics markup language, its design includes the basic capabilities of a page description language (PDL), like Adobe's PDF. It contains provisions for rich graphics, and is also compatible with CSS for styling purposes. It is unlike XHTML, whose primary purpose is communication of content, not presentation, and therefore specifies objects to be displayed but not where to place such objects. Conversely SVG is an ideal PDL for print-oriented uses, as it contains all the functionality required to place each glyph and image in a chosen location on the final page.^[6] A much more print-specialized subset of SVG (SVG Print, authored by Canon, HP, Adobe and Corel) is currently^[update] a W3C Working Draft.^[7]

Scripting and animation[link]

SVG drawings can be dynamic and interactive. Time-based modifications to the elements can be described in SMIL, or can be programmed in a scripting language (e.g., ECMAScript or JavaScript). The W3C explicitly recommends SMIL as the standard for animation in SVG.^[8] A rich set of event handlers such as onmouseover and onclick can be assigned to any SVG graphical object.

Compression[link]

SVG images, being XML, contain many repeated fragments of text, so they are well suited for lossless data compression algorithms. When an SVG image has been compressed with the industry standard gzip algorithm, it is referred to as an "SVGZ" image and uses the corresponding .svgz filename extension. Conforming SVG 1.1 viewers will display compressed images.^[9] An SVGZ file is typically 20 to 50 percent of the original size.^[10] W3C provides SVGZ files to test for conformance.^[11]

Development history[link]

SVG was developed by the W3C SVG Working Group starting in 1998, after Macromedia and Microsoft introduced VML whereas Adobe Systems and Sun Microsystems submitted a competing format known as PGML. The working group was chaired by Chris Lilley of the W3C.

• SVG 1.0 became a W3C Recommendation on 4 September 2001.^[12]
• SVG 1.1 became a W3C Recommendation on 14 January 2003.^[13] The SVG 1.1 specification is modularized in order to allow subsets to be defined as profiles. Apart from this, there is very little difference between SVG 1.1 and SVG 1.0.
  • SVG Tiny and SVG Basic (the Mobile SVG Profiles) became W3C Recommendations on 14 January 2003. These are described as profiles of SVG 1.1.^[14]
• SVG Tiny 1.2 became a W3C Recommendation on 22 December 2008.^[15]
• SVG Full 1.2 has had a W3C Working Draft in process for years, but now will be dropped soon in favor of a SVG 2.0.^[16] SVG Tiny 1.2 was initially released as a profile and later refactored to be a complete specification, including all needed parts of SVG 1.1 and SVG 1.2. SVG 1.2 Full adds modules onto the SVGT 1.2 core.
• SVG Print adds syntax for multi-page documents and mandatory color management support.
• SVG 1.1 Second Edition, which includes all the errata and clarifications, but no new features to the original SVG 1.1 was released on August 16, 2011.^[17]
• SVG 2.0 will completely rework draft 1.2 with more integration with new web features such as CSS, HTML5 and WOFF. It is scheduled as "recommendation" for August 2013.^[18]

The MPEG-4 Part 20 standard - Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF) is based on SVG Tiny.^[19] It was developed by MPEG (ISO/IEC JTC1/SC29/WG11) and published as ISO/IEC 14496-20:2006.^[20] SVG capabilities are enhanced in MPEG-4 Part 20 with key features for mobile services, such as dynamic updates, binary encoding, state-of-art font representation.^[21] SVG was also accommodated in MPEG-4 Part 11, in the Extensible MPEG-4 Textual (XMT) format - a textual representation of the MPEG-4 multimedia content using XML.^[22]

Mobile profiles[link]

Because of industry demand, two mobile profiles were introduced with SVG 1.1: SVG Tiny (SVGT) and SVG Basic (SVGB). These are subsets of the full SVG standard, mainly intended for user agents with limited capabilities. In particular, SVG Tiny was defined for highly restricted mobile devices such as cellphones, and SVG Basic was defined for higher-level mobile devices, such as PDAs.

In 2003, the 3GPP, an international telecommunications standards group, adopted SVG Tiny as the mandatory vector graphics media format for next-generation phones. SVGT is the required vector graphics format and support of SVGB is optional for Multimedia Messaging Service (MMS) and Packet-switched Streaming Service (PSS).^[23][24][25] It was later added as required format for vector graphics in 3GPP IP Multimedia Subsystem (IMS).^[26] Neither mobile profile includes support for the full DOM, while only SVG Basic has optional support for scripting, but because they are fully compatible subsets of the full standard, most SVG graphics can still be rendered by devices which only support the mobile profiles.^[27]

SVGT 1.2 adds a microDOM (μDOM), allowing all mobile needs to be met with a single profile.

Functionality[link]

The SVG 1.1 specification defines 14 functional areas or feature sets:^[13]

Paths

Simple or compound shape outlines are drawn with curved or straight lines that can be filled in, outlined, or used as a clipping path. Paths have a compact coding. For example M (for 'move to') precedes initial numeric x and y coordinates and L (line to) precedes a point to which a line should be drawn. Further command letters (C, S, Q, T and A) precede data that is used to draw various Bézier and elliptical curves. Z is used to close a path. In all cases, absolute coordinates follow capital letter commands and relative coordinates are used after the equivalent lower-case letters.^[28]

Basic shapes

Straight-line paths and paths made up of a series of connected straight-line segments (polylines), as well as closed polygons, circles and ellipses can be drawn. Rectangles and round-cornered rectangles are also standard elements.^[29]

Text

Unicode character text included in an SVG file is expressed as XML character data. Many visual effects are possible, and the SVG specification automatically handles bidirectional text (for composing a combination of English and Arabic text, for example), vertical text (as Chinese was historically written) and characters along a curved path (such as the text around the edge of the Great Seal of the United States).^[30]

Painting

SVG shapes can be filled and/or outlined (painted with a color, a gradient, or a pattern). Fills can be opaque or have any degree of transparency. "Markers" are line-end features, such as arrowheads, or symbols that can appear at the vertices of a polygon.^[31]

Color

Colors can be applied to all visible SVG elements, either directly or via 'fill', 'stroke,' and other properties. Colors are specified in the same way as in CSS2, i.e. using names like black or blue, in hexadecimal such as #2f0 or #22ff00, in decimal like rgb(255,255,127), or as percentages of the form rgb(100%,100%,50%).^[32]

Gradients and patterns

SVG shapes can be filled or outlined with solid colors as above, or with color gradients or with repeating patterns. Color gradients can be linear or radial (circular), and can involve any number of colors as well as repeats. Opacity gradients can also be specified. Patterns are based on predefined raster or vector graphic objects, which can be repeated in x and/or y directions. Gradients and patterns can be animated and scripted.^[33]

Since 2008, there has been discussion^[34][35] among professional users of SVG that either gradient meshes or preferably diffusion curves could usefully be added to the SVG specification. It is said that a "simple representation [using diffusion curves] is capable of representing even very subtle shading effects"^[36] and that "Diffusion curve images are comparable both in quality and coding efficiency with gradient meshes, but are simpler to create (according to several artists who have used both tools), and can be captured from bitmaps fully automatically."^[37]

Clipping, masking and compositing

Graphic elements, including text, paths, basic shapes and combinations of these, can be used as outlines to define both 'inside' and 'outside' regions that can be painted (with colors, gradients and patterns) independently. Fully opaque clipping paths and semi-transparent masks are composited together to calculate the color and opacity of every pixel of the final image, using alpha blending.^[38]

Filter effects^[39]

Interactivity

SVG images can interact with users in many ways. In addition to hyperlinks as mentioned below, any part of an SVG image can be made receptive to user interface events such as changes in focus, mouse clicks, scrolling or zooming the image and other pointer, keyboard and document events. Event handlers may start, stop or alter animations as well as trigger scripts in response to such events.^[40]

Linking

SVG images can contain hyperlinks to other documents, using XLink. URLs of SVG images can specify geometrical transforms in the fragment section.^[41]

Scripting

All aspects of an SVG document can be accessed and manipulated using scripts in a similar way to HTML. The default scripting language is ECMAScript (closely related to JavaScript) and there are defined Document Object Model (DOM) objects for every SVG element and attribute. Scripts are enclosed in <script> elements. They can run in response to pointer events, keyboard events and document events as required.^[42]

Animation

SVG content can be animated using the built-in animation elements such as <animate>, <animateMotion> and <animateColor>. Content can be animated by manipulating the DOM using ECMAScript and the scripting language's built-in timers. SVG animation has been designed to be compatible with current and future versions of Synchronized Multimedia Integration Language (SMIL). Animations can be continuous, they can loop and repeat, and they can respond to user events, as mentioned above.^[43]

Fonts

As with HTML and CSS, text in SVG may reference external font files, such as system fonts. If the required font files do not exist on the machine where the SVG file is rendered, the text may not appear as intended. To overcome this limitation, text can be displayed in an 'SVG font', where the required glyphs are defined in SVG as a font that is then referenced from the <text> element.^[44]

Metadata

In accord with the W3C's Semantic Web initiative, SVG allows authors to provide metadata about SVG content. The main facility is the <metadata> element, where the document can be described using Dublin Core metadata properties (e.g., title, creator/author, subject, description, etc). Other metadata schemas may also be used. In addition, SVG defines <title> and <desc> elements where authors may also provide plain-text descriptive material within an SVG image to help indexing, searching and retrieval by a number of means.^[45]

An SVG document can define components including shapes, gradients etc., and use them repeatedly. SVG images can also contain raster graphics, such as PNG and JPEG images, and further SVG images.

SVG on the web[link]

Google announced on 31 August 2010 that it had started to index SVG content on the web, whether it is in standalone files or embedded in HTML, and that users would begin to see such content listed among their search results.^[46] It was announced on 8 December 2010 that Google Image Search would also begin indexing SVG files.^[47] On 28 January 2011, it was discovered that Google was allowing Image Search results to be restricted exclusively to SVG files.^[48] This feature was announced officially on 11 February 2011.^[49]

Support for SVG in web browsers[link]

The use of SVG on the web is still limited by the lack of support in older versions of Internet Explorer (IE) which (as of June 2012) is the second most widely used browser, behind Chrome.^[50] The most widely deployed version of IE (version 8) does not support SVG.^[51][52] However, IE9 (released March 14, 2011) does support the basic SVG feature set.^[53] Many web sites that serve SVG images, such as Wikipedia, also provide the images in a raster format, either automatically by HTTP content negotiation or by allowing the user directly to choose the file.

Native support[link]

Konqueror was the first browser to support SVG in release version 3.2 in February 2004.^[54] As of 2011, all major desktop browsers, and many minor ones, have some level of SVG support. Other browsers' implementations are not yet complete; see comparison of layout engines for further details.

Some earlier versions of Firefox (e.g., versions between 1.5 and 4.0^[55]) and some other outdated web browsers that can display SVG graphics needed them embedded in <object> or <iframe> elements to display them integrated as parts of an HTML webpage instead of using the standard way of integrating images with <img>.^[56] However, SVG images may be included in XHTML pages using XML namespaces.^[57]

Tim Berners-Lee, the inventor of the World Wide Web, had been critical of Internet Explorer for its failure to support SVG.^[58]

• Opera (since 8.0) has support for the SVG 1.1 Tiny specification while Opera 9 includes SVG 1.1 Basic support and some of SVG 1.1 Full. Opera 9.5 has partial SVG Tiny 1.2 support. It also supports SVGZ (compressed SVG).
• Browsers based on the Gecko layout engine (such as Firefox, Flock, Camino, and SeaMonkey) all have had incomplete support for the SVG 1.1 Full specification since 2005. The Mozilla site has an overview of the modules which are supported in Firefox^[59] and of the modules which are in progress in the development.^[60] Gecko 1.9, included in Firefox 3.0, adds support for more of the SVG specification (including filters).^[61]
• Browsers based on WebKit (such as Apple's Safari, Google Chrome, and The Omni Group's OmniWeb) have had incomplete support for the SVG 1.1 Full specification since 2006.^[62]
• Amaya has partial SVG support.
• Native support became partially available in Internet Explorer 9 (the current version of IE, as of March 2011).^[53]

There are several advantages to native and full support: plugins are not needed, SVG can be freely mixed with other content in a single document, and rendering and scripting become considerably more reliable.^{[citation needed]}

Compatibility[link]

Internet Explorer, up to and including IE8, was the only major browser not to provide native SVG support. IE8 and older require a plug-in to render SVG content. There are a number of plug-ins available to assist, including:

• Ample SDK Open-Source JavaScript GUI Framework provides partial support for SVG 1.1, SMIL, DOM and style scripting in Internet Explorer (5.5 - 8.0) too. It is not dependent on any plugins and relies on presence of alternative Vector Graphics format VML in Internet Explorer.
• Batik, a widely deployed Java plugin^[63]
• Google Chrome Frame from Google can support all web elements supported by WebKit, including SVG 1.0 and partially SVG 1.1.
• GPAC, targets SVGT 1.2^[64]
• Adobe SVG Viewer from Adobe Systems plugin supports most of SVG 1.0/1.1. Zooming and panning of the image are also supported to enable viewing of any area of the SVG lying outside the visible area of its containing window, but scrolling is not supported. Adobe SVG Viewer is available for download from Adobe Systems free of charge.^[65] However, on 1 January 2009, Adobe Systems discontinued support for Adobe SVG Viewer.^[66]
• Corel SVG Viewer^[67] (discontinued)
• Raphaël is another JavaScript library that takes advantage of the intersection between VML's and SVG's features to create vector graphics and animate them.
• Renesis Player for Internet Explorer from examotion GmbH, supports SVG 1.1 on IE 6 and 7 (discontinued)^[68]
• SVG Web^[69] is a JavaScript library for Web developers, targeted at Internet Explorer and dependent on the presence of an installed Adobe Flash plugin on the client machine. SVG Web provides partial support for SVG 1.1, SVG Animation (SMIL), Fonts, Video and Audio, DOM and style scripting.^[70]

On January 5, 2010, a senior manager of the Internet Explorer team at Microsoft announced on his official blog that Microsoft had just requested to join the SVG Working Group of the W3C in order to "take part in ensuring future versions of the SVG spec will meet the needs of developers and end users," although no plans for SVG support in Internet Explorer were mentioned at that time.^[71] Internet Explorer 9 beta supported a basic SVG feature set based on the SVG 1.1 W3C recommendation. Functionality has been implemented for most of the SVG document structure, interactivity through scripting and styling inline and through CSS. The presentation elements, attributes and DOM interfaces that have been implemented include basic shapes, colors, filling, gradients, patterns, paths and text.^[72]

Software and support in applications[link]

SVG images can be produced by the use of a vector graphics editor, such as Inkscape, Adobe Illustrator, or CorelDRAW, and rendered to common raster image formats such as PNG using the same software.

Software can be programmed to render SVG images by using a library such as librsvg or Batik. SVG images can also be rendered to any desired popular image format by using the free software command-line utility ImageMagick.

Web browsers which can display SVG images on web pages include Firefox, Internet Explorer (IE 9+), Opera, Safari and Google Chrome.

SVG on the desktop has also become common. The GNOME project has supported and extensively used SVG icons since 2000.

Other uses for SVG include embedding for use in word processing (e.g. with LibreOffice) and desktop publishing (e.g., Scribus), plotting graphs (e.g., gnuplot), and importing paths (e.g., for use in GIMP or Blender).

Mobile support[link]

Many smart phones have support for SVG, but primarily limited by their respective operating system. Adobe Flash Lite has optionally supported SVG Tiny since version 1.1. At the SVG Open 2005 conference, Sun demonstrated a mobile implementation of SVG Tiny 1.1 for the Connected Limited Device Configuration (CLDC) platform.^[73]

Mobiles which use Opera Mobile as well as the iPhone's built in browser, also include SVG support. However, even though it used the WebKit engine, the Android built-in browser did not support SVG prior to v3.0 (Honeycomb).^[74] Prior to v3.0, Firefox Mobile 4.0b2 (beta) for Android was the first browser running under Android to support SVG by default.^[75]

The level of SVG Tiny support available varies from mobile to mobile, depending on the SVG engine installed. Many newer mobile products support additional features beyond SVG Tiny 1.1, like gradient and opacity; this standard is often referred as SVGT 1.1+. The iPhone, for example, supports declarative animation but not interactivity.

Rim's BlackBerry has built-in support for SVG TIny 1.1 since version 5.0.^[76] Support continues for WebKit-based BlackBerry Torch browser in OS 6 and 7.^[77]

Nokia's S60 platform has built-in support for SVG. For example, icons are generally rendered using the platform's SVG engine. Nokia has also led the JSR 226: Scalable 2D Vector Graphics API expert group which defines Java ME API for SVG presentation and manipulation. This API has been implemented in S60 Platform 3rd Edition Feature Pack 1 onward.^[78] Some Series 40 phones also support SVG (such as Nokia 6280).

Most Sony Ericsson phones beginning with K700 (by release date) support SVG Tiny 1.1. Phones beginning with K750 also support such features as opacity and gradients. Phones with Sony Ericsson Java Platform-8 have support for JSR 226.

Windows Phone 7 has supported SVG since September 2011; however Internet Explorer Mobile, the browser bundled with the operating system has no native SVG support.

SVG is also supported on various mobile devices from Motorola, Samsung, LG and Siemens mobile/BenQ-Siemens. eSVG, an SVG rendering library mainly written for embedded devices, is available on many mobile platforms.^[79][80]

Hardware rendering[link]

This unreferenced section requires citations to ensure verifiability.

Implementations of SVG that uses the OpenVG API will be hardware accelerated on devices which have hardware acceleration of OpenVG. Examples include Unix-like operating systems with Gallium3D based graphics drivers and several GPUs intended for handheld devices (see OpenVG).

See also[link]

References[link]

External links[link]

Wikibooks has a book on the topic of XML - Managing Data Exchange/SVG

• W3C SVG page specifications, list of implementations
• W3C SVG primer W3C Primer (draft) under auspices of SVG Interest Group
• Army Civilian Employment An example of an SVG website delivered as HTML with a non-standard <embed> tag. Works in Firefox, Chrome, Opera, Safari, IE7 w/Adobe and IE8 w/Adobe.
• Army Civilian Service An example of an SVG website delivered as SVG. Works in Firefox, Chrome, Opera, Safari, IE9, IE8 w/Adobe and IE7 w/Adobe.
• Scalable Vector Graphics at the Open Directory Project
• Compatibility tables for features in HTML5, CSS3, SVG and other upcoming web technologies
• SVG examples Many examples of SVG animation, Filters and Tiling.
• SVG Elves Tutorials and code snippets shared by the SVG community.