Now we're ready to start distorting our beautiful images. But first, let's formally introduce the
<g> element. With this helper, you can assign properties to a complete set of elements. Actually, that's its only purpose. An example:
<g fill="red"> <rect x="0" y="0" width="10" height="10" /> <rect x="20" y="0" width="10" height="10" /> </g>
This results in two red rectangles.
All following transformations are summed up in an element's
transform attribute. Transformations can be chained simply by concatenating them, separated by whitespace.
It may be necessary to move an element around, even though you can position it with the according attributes. For this purpose, the
translate() transformation stands ready.
<rect x="0" y="0" width="10" height="10" transform="translate(30,40)" />
The example will render a rectangle, translated to the point (30,40) instead of (0,0).
If the second value is not given, it is assumed to be 0.
Rotating an element is quite a common task. Use the
rotate() transformation for this:
<rect x="20" y="20" width="20" height="20" transform="rotate(45)" />
This example shows a square that is rotated by 45 degrees. The value for
rotate() is given in degrees.
To make a rhombus out of our rectangle, the
skewY() transformations are available. Each one takes an angle that determines how far the element will be skewed.
scale() changes the size of an element. It takes two numbers, evaluated as ratio by which to scale. 0.5 shrinks by 50%. If the second number is omitted, it is assumed to be equal to the first.
Complex transformations with
All the above transformations can be expressed by a 3x3 transformation matrix. To combine several transformations, one can set the resulting matrix directly with the
matrix(a, b, c, d, e, f) transformation which maps coordinates from a new coordinate system into a previous coordinate system by
See a concrete example on the SVG transform documentation. Detailed information about this property can be found in the SVG Recommendation.
Effects on Coordinate Systems
When using transformations you establish a new coordinate system inside the element the transformations apply to. That means, the units you specify for the element and its children might not follow the 1:1 pixel mapping, but are also distorted, skewed, translated and scaled according to the transformation.
<g transform="scale(2)"> <rect width="50" height="50" /> </g>
The resulting rectangular in the above example will be 100x100px. The more intriguing effects arise, when you rely on attributes like
userSpaceOnUse and the such.
Embedding SVG in SVG
In contrast to HTML SVG allows you to embed other
svg elements seamlessly. This way you can also simply create new coordinate systems by utilizing the
height of the inner
<svg xmlns="http://www.w3.org/2000/svg" version="1.1"> <svg width="100" height="100" viewBox="0 0 50 50"> <rect width="50" height="50" /> </svg> </svg>
The example above has basically the same effect as the one above, namely that the rect will be twice as large as specified.