Courses/Design & Technique-Essential Web Design/Q2/01

SVG

What is SVG?

SVG (Scalable Vector Graphics) is a vector image format.

Contrary to raster graphics or bit maps (an image represented by a rectangular grid of pixels) a vector image is a description of its geometric shapes, or drawing instructions, which the viewing

program will draw on the screen.

SVG Characteristics

• scalable - zooms wont pixelate or degrade the image quality
• text-based image format - like a webpage you can view and change the source code of an SVG image
• editable in vector drawing software (Inkscape, Adobe Illustrator)
• easily included within an HTML document
• syntax similar to HTML

SVG: image and text

This SVG image is the representation of the following SVG code:

You can use the inspector, a text-editor, or a vector drawing program to change the image.

<svg
   xmlns:dc="http://purl.org/dc/elements/1.1/"
   xmlns:cc="http://creativecommons.org/ns#"
   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
   xmlns:svg="http://www.w3.org/2000/svg"
   xmlns="http://www.w3.org/2000/svg"
   version="1.1"
   width="300"
   height="200"
   id="svg3910">
  <g
     transform="translate(0,-852.36218)"
     id="layer1">
    <rect
       width="200"
       height="140"
       x="92.85714"
       y="908.07648"
       id="rect3017"
       style="opacity:1;fill:#3964c8;stroke:none" />
    <path
       d="m 254.28571,269.50504 a 74.285713,71.428574 0 1 1 -148.57142,0 74.285713,71.428574 0 1 1 148.57142,0 z"
       transform="translate(-95.714287,658.57142)"
       id="path3015"
       style="opacity:1;fill:#ff64c8;stroke:none" />
  </g>
</svg>

dimensions

Notice the height and width arguments in the example above. They determine how large the svg drawing space will be, in pixels.

width="300"
height="200"

SVG basic shapes

As you can see in the example above an SVG is made up from basic shapes, that combined, styled, transformed and grouped can form complex drawings.

The basic shapes are:

• line

 <line x1="40" y1="20" x2="80" y2="20" style="stroke-width: 10; stroke: black;"/>

• rectangle

<rect x="50" y="10" width="20" height="40" style="fill: none; stroke: black;"/>

• circle

 <circle cx="30" cy="30" r="20" style="stroke: black; fill: red;"/>

• ellipse

 <ellipse cx="80" cy="80" rx="20" ry="10" style="stroke: black; fill: none;"/>

• polygon - series of points that describe a geometric area to be filled and outlined

 <polygon points="15,10  55, 10  45, 20  5, 20"
   style="fill: red; stroke: black;"/>

• group - the group <g> element is not a shape, but element that gathers all of its child elements into one block

SVG with custom fonts

This is just the basics. We'll want to manipulate the SVG drawings further, not just style them with CSS, but:

• add drawing elements,
• remove them,
• turn elements into links,
• transform the image based on user interaction
• create a new image every time a user visits the site,
• etc.

To create those actions with need a scripting language for the browser.

(WHAT IS A SCRIPTING LANGUAGE?)