NOTE: This page has been replaced by https://authors.ietf.org/diagrams
The schema in use for SVG in RFCs is SVG-1.2-RFC.rnc. Please see the FAQ for more information.
The version of SVG that will be allowed in RFCs is described in RFC 7996, “SVG Drawings for RFCs: SVG 1.2 RFC”. Its formal syntax will be updated in 7996-bis (see the GitHub repository).
As one of the tools for using SVG 1.2 RFC, we have produced svgcheck, a Python program that will read SVG files, check whether they conform to SVG 1.2 RFC, and delete from them anything that doesn't conform. When you've made an SVG diagram, you should run it through svgcheck, and take a careful look at the resulting new SVG diagram to see that no features that you need have been deleted.
Many people have asked for advice about how best to create SVG diagrams; in this note I summarise my experiences of doing that. To start with, Wikipedia has a good survey of both Open Source and Proprietary packages at Comparison_of_vector_graphics_editors.
Of the Open Source packages, in my opinion Inkscape is the best of them. It's a big package, though, with many features, so there's a big learning curve to go through. Fortunately there's a lot of tutorial material on the web, for example: Inkscape tutorial Note, however, that SVG 1.2 RFC only allows objects that are part of black-and-white line drawings.
Again, Inkscape uses markers for line-end symbols (even if you create your own markers using Object → Objects to Marker). That means, if you want arrowheads at the end of lines, you have to draw them in yourself. The simplest way to do that is to make an arrowhead with two lines grouped together, draw your lines, then copy your arrowhead at the end(s) of them.
Another nice feature of Inkscape is that its 'Resize page to content' lets you resize your svg drawing to trim the white space around its edges before you save it as 'Plain SVG'. An example SVG flowchart diagram produced in this way is linked to below.
This is good if you're used to LibreOffice, and your drawing is fairly simple.
Create your drawing using Draw, group it into a single object, then export it. (For me, that makes an SVG diagram that emacs and Inkscape display properly, but Firefox donesn't - however, check-svg.py's rewritten SVG diagram displays properly in Firefox, with Draw's arrowheads displayed properly.)
Runs on Windows, OSX, GNU/Linux and Unix. Install it from http://dia-installer.de
Dia is simple to use. Save your drawing as xxx.dia, then export it as xxx.svg.
Dia draws line-end arrowheads as filled polygons, and it doesn't use markers.
If you're familiar with Adobe Illustrator, it can also be used. It can save files as SVG-t (i.e. SVG Tiny), which - I assume - means that drawings saved in SVG-t don't use arrowheads.
If you have black and white diagrams in PowerPoint these can be copied and pasted into Inkscape. You can resize and position on Inkscape's default page or you can create a drawing size and adjust. Then you can save as a plain svg. PowerPoint can save natively into SVG as well but that SVG is very detailed.
The plain SVG will have:
width="210mm" height="279mm" viewBox="0 0 210 279"
(or whatever your starting size was)
It is easier to make Inkscape drawing size close to the dimensions you want before saving. For a 1/2 page drawing a full page may be used and the height can be adjusted, but sometimes the conversion will complain and the height/width have to be removed. See positioning tips.)
Editing the basic svg:
You will need to remove clipPath and metadata (it will probably look something like this):
<defs id="defs2"> <clipPath id="clip0"> <rect x="52" y="349" width="2159" height="889" id="rect10" /> </clipPath> </defs> <metadata id="metadata5"> <rdf:RDF> <cc:Work rdf:about=""> <dc:format>image/svg+xml</dc:format> <dc:type rdf:resource="http://purl.org/dc/dcmitype/StillImage" /> <dc:title></dc:title> </cc:Work> </rdf:RDF> </metadata>
The basic svg has some identifiers that must be removed:
font-weight font-family style="stroke-width:0.0911541"<...
The font-related ones can usually be deleted by deleting the whole line. The style one is part of a tspan tag and you must only remove the text. These VIM command line commands do it properly:
:1,$s/style="stroke.*"// :g/font-weight/d :g/font-family/d
At this point you can test the SVG either by including and running it in xml2rfc or using the SVG tester but xml2rfc catches more issues so I skip the tester. Rendering:
xml2rfc --pdf your_v3_xml_draft.xml
Another issue is with <tspans>. It seems text is expanded to text and tspan tags.
Sometimes the physical text is between
and sometimes it is between
which is fine but with hyphenated text there are two issues. It might put the text between the tspan and text tags:
And you need to correct it by either moving the text or deleting the tags. The xml2rfc --pdf will complain about this. Simply moving the text inside the tspan tags works.
Usually there are coordinates within the text and tspan tags - you want to keep those. Another issue is the coordinates of the text can cause the characters to overwrite in different tspans.
<text><tspan>fouled-up</tspan></text> will print better than <text><tspan>fouled</tspan>-up</tspan></text>.
Positioning: The ViewBox has x-min y-min
x="0" y="0" width="100%" height="100%"/
For a half page drawing from the original:
width="210mm" height="279mm" viewBox="0 0 210 279" x y w% h%
The height controls the whitespace; if your drawing is 1/2 page you can usually reduce by 1/2 and it will only take 1/2 a page. Inch-based dimensions were harder to work with, and width and height had to be removed, but with mm dimensions the height could be reduced more before it complained. The x y controls move the origin; positive values for y move the origin down and the drawing upwards.
Adjusted for 1/2 page it might look like this:
width="210mm" height="110mm" viewBox="0 15 210 110"
Note that the x dimension is unchanged; also, in my experience, the scaling is far from linear. A slightly large diagram needed these values but the difference from 50 to 30 on the veiwBox height was hardly noticeable.
width="210mm" height="135mm" viewBox="0 52 210 30"
The scaling is constant whether the drawing is at the top or following other drawings. Two pictures easily fit with captions on a page using this.