SPS - SVG

Before you continue, you should have some basic understanding of the following:
  • HTML
  • Basic XML

Základ

  • SVG stands for Scalable Vector Graphics
  • SVG is used to define vector-based graphics for the Web
  • SVG defines the graphics in XML format
  • SVG graphics do NOT lose any quality if they are zoomed or resized
  • Every element and every attribute in SVG files can be animated
  • SVG is a World Wide Web Consortium (W3C) recommendation
  • SVG integrates with other W3C standards such as the DOM and XSL

SVG History & Advantages

SVG 1.1 became a W3C Recommendation in January 2003.

Sun Microsystems, Adobe, Apple, IBM, and Kodak are some of the organizations that have been involved in defining SVG.

Advantages of using SVG over other image formats (like JPEG and GIF) are:
  • SVG files can be read and modified by a large range of tools (e.g. notepad)
  • SVG files are smaller and more compressible than JPEG and GIF images
  • SVG images are scalable
  • SVG images can be printed with high quality at any resolution
  • SVG images are zoomable. Any part of the image can be zoomed without degradation
  • Text in SVG is selectable and searchable (excellent for making maps)
  • SVG works with Java technology
  • SVG is an open standard
  • SVG files are pure XML

The main competitor to SVG is Flash.

The biggest advantage SVG has over Flash is the compliance with other standards (e.g. XSL and the DOM). Flash relies on proprietary technology that is not open source.

A drawback of SVG at the moment is that not all browsers support it. Mozilla browsers, Firefox, and Opera support SVG, and Microsoft plan to support SVG.

The number of SVG editors are growing, and Adobe GoLive 5 supports SVG.

SVG Example

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="red"/>
</svg>


The first line contains the XML declaration. Notice the standalone attribute! This attribute specifies whether the SVG file "stands alone", or contains a reference to an external file.

standalone="no" means that the SVG document has a reference to an external file - in this case, the DTD.

The second and the third line refer to the external SVG DTD. The DTD is located at "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd". The DTD resides at the W3C and it contains all allowable SVG elements.

The SVG code begins with the <svg> element, which consists of the opening <svg> tag and the closing </svg> tag. This is the root element. The width and height attributes set the width and height of the SVG document. The version attribute defines the SVG version to be used and the xmlns attribute defines the SVG namespace.

The SVG <circle> element is used to create a circle. The cx and cy attributes define the x and y coordinates of the center of the circle. If cx and cy are omitted, the circle's center is set to (0, 0). The r attribute defines the radius of the circle.

The stroke and stroke-width attributes control how the outline of a shape appears. We set the outline of the circle to a 2px wide, black "border".

The fill attribute refers to the color inside a shape. We set the fill color to red.

The closing </svg> tag closes the root SVG element and the document.

Note: All opening tags must have closing tags!

SVG in HTML Pages

The <embed> tag is supported in all major browsers, and allows scripting.

Note: The Adobe SVG Viewer recommends that you use the EMBED tag when embedding SVG in HTML pages! However, if you want to create valid XHTML, you cannot use <embed> - The <embed> tag is not listed in any HTML specification. 

<embed src="files/sps/kruh.svg" width="300" height="100" type="image/svg+xml" pluginspage="http://www.adobe.com/svg/viewer/install/" />

SVG Shapes

SVG has some predefined shape elements that can be used and manipulated by developers:
  • Rectangle <rect>
  • Circle <circle>
  • Ellipse <ellipse>
  • Line <line>
  • Polyline <polyline>
  • Polygon <polygon>
  • Path <path>

The <rect> Tag

The <rect> tag is used to create a rectangle and variations of a rectangle shape. 
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<rect x="20" y="20" width="250" height="50" style="fill:blue;stroke:orange;stroke-width:5; fill-opacity:0.1;stroke-opacity:0.9"/>
</svg>
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<rect x="20" y="20" rx="20" ry="20" width="250" height="100" style="fill:orange;stroke:black; stroke-width:5;opacity:0.5"/>
</svg>

The <ellipse> Tag

The <ellipse> tag is used to create an ellipse. An ellipse is closely related to a circle. The difference is that an ellipse has an x and a y radius that differs from each other, while a circle has equal x and y radius. 
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<ellipse cx="240" cy="100" rx="220" ry="30" style="fill:purple"/>
	<ellipse cx="220" cy="70" rx="190" ry="20" style="fill:lime; opacity:0.5"/>
	<ellipse cx="210" cy="45" rx="170" ry="15" style="fill:yellow"/>
</svg>

The <line> Tag

The <line> tag is used to create a line. 
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<line x1="0" y1="0" x2="200" y2="50" style="stroke:rgb(99,99,99);stroke-width:2"/>
</svg>
  • The x1 attribute defines the start of the line on the x-axis
  • The y1 attribute defines the start of the line on the y-axis
  • The x2 attribute defines the end of the line on the x-axis
  • The y2 attribute defines the end of the line on the y-axis

The <polygon> Tag

The <polygon> tag is used to create a graphic that contains at least three sides. 
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<polygon points="10,0 20,90 170,80" style="fill:#cccccc; stroke:#000000;stroke-width:1"/>
</svg>

The <polyline> Tag

The <poluline> tag is used to create any shape that consists of only straight lines. 
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<polyline points="0,0 0,20 20,20 20,40 40,40 40,60" style="fill:white;stroke:red;stroke-width:2"/>
</svg>

SVG Filters

The available filters in SVG are:
  • feBlend
  • feColorMatrix
  • feComponentTransfer
  • feComposite
  • feConvolveMatrix
  • feDiffuseLighting
  • feDisplacementMap
  • feFlood
  • feGaussianBlur
  • feImage
  • feMerge
  • feMorphology
  • feOffset
  • feSpecularLighting
  • feTile
  • feTurbulence
  • feDistantLight
  • fePointLight
  • feSpotLight
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg width="100%" height="100%" version="1.1" xmlns="http://www.w3.org/2000/svg">
	<defs>
	<filter id="Gaussian_Blur">
	<feGaussianBlur in="SourceGraphic" stdDeviation="5" />
	</filter>
	</defs>
	<ellipse cx="100" cy="60" rx="70" ry="40" style="fill:#ff0000;stroke:#000000; stroke-width:2;filter:url(#Gaussian_Blur)"/>
</svg>
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