SVG Essentials

Chapter 2. Coordinates

The world of SVG is an infinite canvas. In this chapter, we’ll discuss how you tell a viewer program which part of this canvas you’re interested in, what its dimensions are, and how you locate points within that area.

The Viewport

The area of the canvas that your document intends to use is called the viewport. You establish the size of this viewport with the width and height attributes on the <svg> element. The values of these attributes can be simply a number, which is presumed to be in pixels; this is said to be specified in user coordinates. You may also specify width and height as a number followed by a unit identifier, which can be one of the following:

em

The font size of the default font, usually equivalent to the height of a character

ex

The height of the letter x

px

Pixels

pt

Points (¹/₇₂ of an inch)

pc

Picas (¹/₆ of an inch)

cm

Centimeters

mm

Millimeters

in

Inches

Examples:

<svg width="200" height="150"><svg width="200px" height="200px">

Both of these specify an area 200 pixels wide and 150 pixels tall.

<svg width="2cm" height="3cm">

Specifies an area two centimeters wide and three centimeters high.

<svg width="2cm" height="36pt">

It is possible, though unusual, to mix units; this element specifies an area two centimeters wide and thirty-six points high.

If you have one <svg> element nested within another <svg> element, the nested tag may also specify its width and height as a percentage, measured in terms of the enclosing element. We will see nested <svg> elements in ...