Embedded Content — SVG 2 (2024)

12.1. Overview

Embedded content is content that imports another resource into the document, or content from another vocabulary that is inserted into the document.This is the same definition as HTML's embedded content.

SVG supports embedded content with the use of ‘image’ and ‘foreignObject’ elements.

Additionally SVG allows embedded content using HTML 'video', 'audio', 'iframe' and 'canvas' elements.

Except ‘canvas’ and ‘foreignObject’, embedded content is compatible with Resource Hints for prioritizing downloading of external resources.

12.2. Placement of the embedded content

The x, y, width, and height geometry properties specify the rectangular region into which the embedded content is positioned (the positioning rectangle). The positioning rectangle is used as the bounding box of the element; note, however, that graphics may overflow the positioning rectangle, depending on the value of the overflow property.

When the embedded content consists of a single referenced resource (e.g., an ‘image’, ‘video’, or ‘canvas’), the dimensions of the positioning rectangle, in the current coordinate system after applying all transforms, define the specified size for the embedded object. A concrete object size and final position must be determined for the object using the Default Sizing Algorithm defined for replaced elements in CSS layout [css-images-3]. The object-fit and object-position affect the final position and size of the object, and may cause it to be extend beyond the positioning rectangle. In that case, the overflow property determines whether the rendered object should be clipped to its positioning rectangle.

When the embedded content consists of a document fragment (e.g., a ‘foreignObject’, an ‘audio’ or ‘video’ with user-agent generated controls, or a ‘video’, ‘audio’, or ‘canvas’ displaying HTML fallback content), the positioning rectangle defines the bounds of a containing block for laying out the child content using CSS. The scale of the containing block is defined in the current coordinate system, including all explicit and implicit (e.g., ‘viewBox’) transformations. The ‘foreignObject’, or other element that is positioned using SVG layout attributes, is implicitly absolutely-positioned for the purposes of CSS layout. As a result, any absolutely-positioned child elements are positioned relative to this containing block. Again, the overflow property determines whether content that extends outside the positioning rectangle will be hidden.

A value of zero for either width or height disables rendering of the element and its embedded content.

The 'auto' value for width or height is used to size the corresponding element automatically based on the intrinsic dimensions or intrinsic aspect ratio of the referenced resource. Computation of automatically-sized values follows the Default Sizing Algorithm defined for replaced elements in CSS layout [css-images-3]. In particular, when the referenced resource does not have an intrinsic size (such as an ‘iframe’ or an image types with no defined dimensions), it is assumed to have a width of 300px and a height of 150px.

CSS positioning properties (e.g. top and margin) have no effect when positioning the embedded content element in the SVG coordinate system. They can, however, be used to position child elements of a ‘foreignObject’ or HTML embedding element.

12.3. The ‘image’ element

‘image’

Categories:

Graphics element, graphics referencing element, renderable element, structurally external element

Content model:

Any number of the following elements, in any order:

• animation elements — ‘animate’, ‘animateMotion’, ‘animateTransform’, ‘discard’, ‘set’
• descriptive elements — ‘desc’, ‘title’, ‘metadata’

clipPath, mask, script, style

Attributes:

• aria attributes — ‘aria-activedescendant’, ‘aria-atomic’, ‘aria-autocomplete’, ‘aria-busy’, ‘aria-checked’, ‘aria-colcount’, ‘aria-colindex’, ‘aria-colspan’, ‘aria-controls’, ‘aria-current’, ‘aria-describedby’, ‘aria-details’, ‘aria-disabled’, ‘aria-dropeffect’, ‘aria-errormessage’, ‘aria-expanded’, ‘aria-flowto’, ‘aria-grabbed’, ‘aria-haspopup’, ‘aria-hidden’, ‘aria-invalid’, ‘aria-keyshortcuts’, ‘aria-label’, ‘aria-labelledby’, ‘aria-level’, ‘aria-live’, ‘aria-modal’, ‘aria-multiline’, ‘aria-multiselectable’, ‘aria-orientation’, ‘aria-owns’, ‘aria-placeholder’, ‘aria-posinset’, ‘aria-pressed’, ‘aria-readonly’, ‘aria-relevant’, ‘aria-required’, ‘aria-roledescription’, ‘aria-rowcount’, ‘aria-rowindex’, ‘aria-rowspan’, ‘aria-selected’, ‘aria-setsize’, ‘aria-sort’, ‘aria-valuemax’, ‘aria-valuemin’, ‘aria-valuenow’, ‘aria-valuetext’, ‘role’
• core attributes — ‘id’, ‘tabindex’, ‘lang’, ‘xml:space’, ‘class’, ‘style’
• conditional processing attributes — ‘requiredExtensions’, ‘systemLanguage’
• global event attributes — ‘oncancel’, ‘oncanplay’, ‘oncanplaythrough’, ‘onchange’, ‘onclick’, ‘onclose’, ‘oncuechange’, ‘ondblclick’, ‘ondrag’, ‘ondragend’, ‘ondragenter’, ‘ondragexit’, ‘ondragleave’, ‘ondragover’, ‘ondragstart’, ‘ondrop’, ‘ondurationchange’, ‘onemptied’, ‘onended’, ‘onerror’, ‘onfocus’, ‘oninput’, ‘oninvalid’, ‘onkeydown’, ‘onkeypress’, ‘onkeyup’, ‘onload’, ‘onloadeddata’, ‘onloadedmetadata’, ‘onloadstart’, ‘onmousedown’, ‘onmouseenter’, ‘onmouseleave’, ‘onmousemove’, ‘onmouseout’, ‘onmouseover’, ‘onmouseup’, ‘onmousewheel’, ‘onpause’, ‘onplay’, ‘onplaying’, ‘onprogress’, ‘onratechange’, ‘onreset’, ‘onresize’, ‘onscroll’, ‘onseeked’, ‘onseeking’, ‘onselect’, ‘onshow’, ‘onstalled’, ‘onsubmit’, ‘onsuspend’, ‘ontimeupdate’, ‘ontoggle’, ‘onvolumechange’, ‘onwaiting’
• document element event attributes — ‘oncopy’, ‘oncut’, ‘onpaste’
• graphical event attributes — ‘onfocusin’, ‘onfocusout’
• deprecated xlink attributes — ‘xlink:href’, ‘xlink:title’
• presentation attributes —
• ‘preserveAspectRatio’
• ‘href’
• ‘crossorigin’

Geometry properties:

• x
• y
• width
• height

DOM Interfaces:

• SVGImageElement

See Also

[HTML] - How to round an image in HTML?Difference between SVG and HTML 5 Canvas - GeeksforGeeks - SVG: Scalable Vector Graphics | MDNA guide to importing SVG icons in HTML

The ‘image’ elementindicates that the contents of a complete file are to berendered into a given rectangle within the current usercoordinate system. The ‘image’ element can refer to rasterimage files such as PNG or JPEG or to files with MIME type of"image/svg+xml". Conforming SVGviewers need to support at least PNG, JPEG and SVG formatfiles.SVG files must be processed in secure animated modeif the current document supports animation,or in secure static mode if the current document is static.

The result of processing an ‘image’ is always a four-channelRGBA result. When an ‘image’element references an image (such as many PNG or JPEGfiles) which only has three channels (RGB), then the effect isas if the object were converted into a 4-channel RGBA imagewith the alpha channel uniformly set to 1. For a single-channel (grayscale)raster image, the effect is as if the object were convertedinto a 4-channel RGBA image, where the single channel from thereferenced object is used to compute the three color channelsand the alpha channel is uniformly set to 1.

The ‘preserveAspectRatio’ attributedetermines how the referenced image is scaled and positioned to fitinto the concrete object size determined from thepositioning rectangle and the object-fit and object-position properties.The result of applying this attribute defines an image-rendering rectangleused for actual image rendering.When the referenced image is an SVG,the image-rendering rectangle definesthe SVG viewport used for rendering that SVG.

The ‘preserveAspectRatio’ calculations are applied after determining the concrete object size, and only have an effect if that size does not match the intrinsic aspect ratio of the embedded image. If a value of object-fit is used that ensures that the concrete object size matches the intrinsic aspect ratio (i.e., any value other than the default fill), then the ‘preserveAspectRatio’ value will have no effect; the image-rendering rectangle will be that determined when scaling and positioning the object with CSS. The ‘preserveAspectRatio’ attribute can therefore be safely used as a fallback for most values of object-fit and object-position; it must be explicitly set to none to turn off aspect ratio control, regardless of object-fit value.

The aspect ratio to use whenevaluating the ‘preserveAspectRatio’ attribute isdefined by the intrinsic aspect ratio of the referenced content.For an SVG file, the aspect ratio is definedin Intrinsic sizing properties of SVG content".For most raster content (PNG, JPEG) the pixel width and height of the image filedefine an intrinsic aspect ratio.Where the embedded image does not have an intrinsic aspect ratio(e.g. an SVG file with neither ‘viewBox’ attribute nor explicit dimensions for theoutermost svg element) the ‘preserveAspectRatio’ attribute isignored;the embedded image is drawn to fill the positioning rectangle defined by the geometry propertieson the ‘image’ element.

For example, if the image element referenced a PNG or JPEGand preserveAspectRatio="xMinYMinmeet", then the aspect ratio of the raster would bepreserved (which means that the scale factor from image'scoordinates to current user space coordinates would be the samefor both X and Y), the raster would be sized as large aspossible while ensuring that the entire raster fits within theviewport, and the top/left of the raster would be aligned withthe top/left of the viewport as defined by the attributes x, y, width and height on the ‘image’ element. If the valueof ‘preserveAspectRatio’ was 'none'then aspect ratio of the image would not be preserved. Theimage would be fit such that the top/left corner of theraster exactly aligns with coordinate (x, y) and the bottom/right corner ofthe raster exactly aligns with coordinate (x+width, y+height).

For ‘image’ elements embedding an SVG image,the ‘preserveAspectRatio’ attribute on the rootelement in the referenced SVG image must be ignored,and instead treated as if it had a value of none.(see ‘preserveAspectRatio’ for details).This ensures that the ‘preserveAspectRatio’ attribute onthe referencing ‘image’ has its intended effect,even if it is none.

When the value of the ‘preserveAspectRatio’ attribute on the ‘image’is not none,the image-rendering rectangle determinedfrom the properties of the ‘image’ elementwill exactly match the embedded SVG's intrinsic aspect ratio.Ignoring the ‘preserveAspectRatio’ attribute from the embedded SVGwill therefore not usually have any effect.The exception is if the aspect ratio of that imageis determined from absolute values for the width and height attributeswhich do not match its ‘viewBox’ aspect ratio.This is an unusual situation that authors are advised to avoid, for many reasons.

The user agent stylesheet sets the value of the overflow propertyon ‘image’ element to hidden.Unless over-ridden by the author, images will therefore be clipped tothe positioning rectangle defined by the geometry properties.

For ‘image’ elements embedding an SVG image,two different overflow values apply.The value specified on the ‘image’ element determineswhether the image-rendering rectangle is clipped to the positioning rectangle.The value on the root element of the referenced SVGdetermines whether the graphics are clipped to the image-rendering rectangle.

New in SVG 2.Previous versions of SVG required that the overflow (and also clip)property on the embedded SVG be ignored.The new rules ensure that an overflowing slice layoutcan be safely used without compromising the overflow control from the referenced image.

To link into particular view of an embedded SVG image, authors can use media fragments as defined in Linking into SVG content. To crop to a specific section of a raster image, authors can use Basic media fragments identifiers [Media Fragments URI 1.0 (basic)]. Either type of fragment may affect the intrinsic dimensions and/or intrinsic aspect ratio of the image.

The resource referenced by the ‘image’ element represents aseparate document which generates its own parse tree anddocument object model (if the resource is XML). Thus, there isno inheritance of properties into the image.

Unlike ‘use’, the ‘image’ element cannot referenceelements within an SVG file.

Attribute definitions:

Name	Value	Initial value	Animatable
crossorigin	[ anonymous | use-credentials ]?	(see HTML definition of attribute)	yes

The crossorigin attribute is a CORS settings attribute, and unless otherwise specified follows the same processing rules as in HTML [HTML].

Name	Value	Initial value	Animatable
href	URL [URL]	(none)	yes

An URL reference identifying the image to render. Refer to the common handling defined for URL reference attributes and deprecated XLink attributes.

The URL is processed and the resource is fetched as described in the Linking chapter.

<?xml version="1.0" standalone="no"?><svg width="4in" height="3in" xmlns="http://www.w3.org/2000/svg"> <desc>This graphic links to an external image </desc> <image x="200" y="200" width="100px" height="100px" href="myimage.png"> <title>My image</title> </image></svg>

Since image references always refer to a complete document, a target-only URL is treated as a link to the same file, which is rendered again as an independent embedded image. Since the embedded image is processed in a secure mode, its own embedded references are not processed, preventing infinite recursion.

<?xml version="1.0" standalone="no"?><svg width="5cm" height="3cm" viewBox="0 0 50 30" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <title>Recursive SVG</title> <desc>An SVG with two recursive image reference to itself. One reference uses the file name as a relative URL, the other uses a target fragment only. When viewed in a processing mode that supports external file references, the embedded images should be rendered; however, the embedded image must be processed in secure mode, so the recursion only happens once. The appearance should be three nested red circles in a bulls-eye pattern; the innermost circle has solid fill because of target styles. </desc> <style type="text/css"> #target:target { fill: red; } </style> <circle id="target" stroke="red" stroke-width="5" fill="none" cx="50%" cy="50%" r="12" /> <image xlink:href="recursive-image.svg" x="25%" y="25%" width="50%" height="50%" /> <image xlink:href="#target" x="45%" y="45%" width="10%" height="10%" /></svg>

12.4. HTML elements in SVG subtrees

The following HTML elements render when included in an SVG subtree as a child of a container element and when using the HTML namespace:

• 'video'
• 'audio'
• 'iframe'
• 'canvas'

<svg xmlns="http://www.w3.org/2000/svg" xmlns:html="http://www.w3.org/1999/xhtml"> <html:video src="file.mp4" controls="controls"> </html:video></svg>

HTML elements, in the HTML namespace, used as children of 'video', 'audio', 'iframe' and 'canvas' elements within an SVG document fragment behave as specified in HTML. This applies in particular to fallback content;if fallback content is rendered,the embedded element behaves like an SVG ‘foreignObject’ element to contain the HTML content.This would occur, for example,for a ‘video’ element if the user agent does not support the specified video formats,or for a ‘canvas’ element if scripting is disabled.

<svg xmlns="http://www.w3.org/2000/svg" xmlns:html="http://www.w3.org/1999/xhtml"> <html:video src="http://example.org/dummyvideo" controls="controls"> <html:p>The video format is not supported by this browser.</html:p> </html:video></svg>

The HTML specification is applicable also for the 'track' and 'source' elements.

<svg xmlns="http://www.w3.org/2000/svg" xmlns:html="http://www.w3.org/1999/xhtml"> <html:video src="file.mp4" controls="controls"> <html:source src="file.webm" type='video/webm;codecs="vp8, vorbis"'/> <html:source src="file.mp4" type='video/mp4;codecs="avc1.42E01E, mp4a.40.2"'/> </html:video></svg>

Other HTML elements in an SVG subtree,other than those inside a ‘foreignObject’ element,must be treated as unknown elements for rendering purposes.

Many HTML elements will be treated as a parse error by the HTML parser, causing the SVG fragment to terminate.

12.5. The ‘foreignObject’ element

SVG is designed to be compatible with other XML languagesfor describing and rendering other types of content.The ‘foreignObject’element allows for inclusion of elements in a non-SVG namespace whichis rendered within a region of the SVG graphic using other user agent processes. Theincluded foreign graphical content is subject to SVGtransformations, filters, clipping, masking and compositing.Examples includeinserting a MathML expression intoan SVG drawing [MathML3],or adding a block of complex CSS-formatted HTML text or form inputs.

The HTML parser treats elements inside the ‘foreignObject’ equivalent to elements inside an HTML document fragment. Any svg or math element, and their descendents, will be parsed as being in the SVG or MathML namespace, respectively; all other tags will be parsed as being in the HTML namespace.

SVG-namespaced elements within a ‘foreignObject’ will not be rendered,except in the situation where a properly defined SVGfragment, including a root ‘svg’ element isdefined as a descendent of the ‘foreignObject’.

A ‘foreignObject’may be used in conjunction with the ‘switch’ element andthe ‘requiredExtensions’ attribute toprovide proper checking for user agent support and provide analternate rendering in case user agent support is notavailable.

This specification does not define how ‘requiredExtensions’ values should be mapped to support for different XML languages; a future specification may do so.

It is not required that SVG user agent support the abilityto invoke other arbitrary user agents to handle embeddedforeign object types; however, all conforming SVG user agentswould need to support the ‘switch’ element andmust be able to render valid SVG elements when they appear asone of the alternatives within a ‘switch’element.

It is expected that commercial Web browsers willsupport the ability for SVG to embedCSS-formatted HTML and also MathML content,with the rendered content subject to transformations and compositing defined in the SVG fragment.At this time, such a capability is not a requirement.

<?xml version="1.0" standalone="yes"?><svg width="4in" height="3in" xmlns = 'http://www.w3.org/2000/svg'> <desc>This example uses the 'switch' element to provide a fallback graphical representation of an paragraph, if XMHTML is not supported.</desc> <!-- The 'switch' element will process the first child element whose testing attributes evaluate to true.--> <switch> <!-- Process the embedded XHTML if the requiredExtensions attribute evaluates to true (i.e., the user agent supports XHTML embedded within SVG). --> <foreignObject width="100" height="50" requiredExtensions="http://example.com/SVGExtensions/EmbeddedXHTML"> <!-- XHTML content goes here --> <body xmlns="http://www.w3.org/1999/xhtml"> <p>Here is a paragraph that requires word wrap</p> </body> </foreignObject> <!-- Else, process the following alternate SVG. Note that there are no testing attributes on the 'text' element. If no testing attributes are provided, it is as if there were testing attributes and they evaluated to true.--> <text font-size="10" font-family="Verdana"> <tspan x="10" y="10">Here is a paragraph that</tspan> <tspan x="10" y="20">requires word wrap.</tspan> </text> </switch></svg>

[Exposed=Window]interface SVGImageElement : SVGGraphicsElement { [SameObject] readonly attribute SVGAnimatedLength x; [SameObject] readonly attribute SVGAnimatedLength y; [SameObject] readonly attribute SVGAnimatedLength width; [SameObject] readonly attribute SVGAnimatedLength height; [SameObject] readonly attribute SVGAnimatedPreserveAspectRatio preserveAspectRatio; attribute DOMString? crossOrigin;};SVGImageElement includes SVGURIReference;

[Exposed=Window]interface SVGForeignObjectElement : SVGGraphicsElement { [SameObject] readonly attribute SVGAnimatedLength x; [SameObject] readonly attribute SVGAnimatedLength y; [SameObject] readonly attribute SVGAnimatedLength width; [SameObject] readonly attribute SVGAnimatedLength height;};