Understanding pictures and other shapes
=======================================

Conceptually, Word documents have two *layers*, a *text layer* and a *drawing
layer*. In the text layer, text objects are flowed from left to right and from
top to bottom, starting a new page when the prior one is filled. In the drawing
layer, drawing objects, called *shapes*, are placed at arbitrary positions.
These are sometimes referred to as *floating* shapes.

A picture is a shape that can appear in either the text or drawing layer. When
it appears in the text layer it is called an *inline shape*, or more
specifically, an *inline picture*.

Inline shapes are treated like a big text character (a *character glyph*). The
line height is increased to accomodate the shape and the shape is wrapped to
a line it will fit on width-wise, just like text. Inserting text in front of it
will cause it to move to the right. Often, a picture is placed in a paragraph
by itself, but this is not required. It can have text before and after it in
the paragraph in which it's placed.

The ``Document.add_picture()`` method adds a specified picture
to the end of the document in a paragraph of its own. However, by digging
a little deeper into the API you can place text on either side of the picture
in its paragraph, or both.

If width and height are not specified in svg, the default size is *72px*.
The ratio of width and height is kept the same as viewbox attribute.