README
1Images
2======
3
4This directory contains images for use in the documentation.
5
6Creating an image
7-----------------
8
9A variety of tools can be used to create an image. The appropriate
10choice depends on the nature of the image. We prefer workflows that
11involve diffable source files.
12
13These tools are acceptable:
14
15- Graphviz (https://graphviz.org/)
16- Ditaa (http://ditaa.sourceforge.net/)
17
18We use SVG as the format for integrating the image into the ultimate
19output formats of the documentation, that is, HTML, PDF, and others.
20Therefore, any tool used needs to be able to produce SVG.
21
22This directory contains makefile rules to build SVG from common input
23formats, using some common styling.
24
25fixup-svg.xsl applies some postprocessing to the SVG files produced by
26those external tools to address assorted issues. See comments in
27there, and adjust and expand as necessary.
28
29Both the source and the SVG output file are committed in this
30directory. That way, we don't need all developers to have all the
31tools installed. While we accept that there could be some gratuitous
32diffs in the SVG output depending the specific tool, let's keep an eye
33on that and keep it to a minimum.
34
35Using an image in DocBook
36-------------------------
37
38Here is an example for using an image in DocBook:
39
40 <figure id="gin-internals-figure">
41 <title>GIN Internals</title>
42 <mediaobject>
43 <imageobject>
44 <imagedata fileref="images/gin.svg" format="SVG" width="100%"/>
45 </imageobject>
46 </mediaobject>
47 </figure>
48
49Notes:
50
51- The real action is in the <mediaobject> element, but typically a
52 <figure> should be wrapped around it and an <xref> to the figure
53 should be put into the text somewhere. Don't just put an image into
54 the documentation without a link to it and an explanation of it.
55
56- Things are set up so that we only need one <imagedata> element, even
57 with different output formats.
58
59- The attribute format="SVG" is required. If you omit it, it will
60 still appear to work, but the stylesheets do a better job if the
61 image is declared as SVG explicitly.
62
63- The width should be set to something. This ensures that the image
64 is scaled to fit the page in PDF output. (Other widths than 100%
65 might be appropriate.)
66
