Tskit: SVG can no longer be converted with ImageMagick

[molpopgen]

This affects creating static content (like manuscripts). I guess this just needs to be documented somewhere?

With 0.3.2, I get the following via convert -density 300 foo.svg foo.png:

Adding -background none doesn't change anything.

Inkscape solves the problem via inkscape -z foo.svg -d 300 --export-filename foo2.png:

rsvg-convert from librsvg2-bin also works, but it is more fiddly to get the final DPI right.

[benjeffery]

I think this is worth fixing - seems a fill attribute should do it?

[jeromekelleher]

Yes, this is a bug. @hyanwong, can you comment please?

[hyanwong]

We have a fill style set in the CSS. It's probable that IM is ignoring the CSS spec for some reason. I'll have a look if there's an easy fix.

[hyanwong]

My version of ImageMagick doesn't like it when the style is wrapped in <![CDATA[ ... ]]>, which is, by default, how the SVG library we use wraps styles. In the CSS docs it says:

Note how the CSS style sheet is placed within a CDATA construct (i.e., ", which conflict with XML parsers. Even if a given style sheet does not use characters that conflict with XML parsing, it is highly recommended that internal style sheets be placed inside CDATA blocks.

We can probably omit it if we want to. See https://stackoverflow.com/questions/55465703/is-cdata-necessary-when-styling-an-inline-svg . Note that wrapping the <![CDATA[ markup in /* ... */, as shown in that SO question doesn't seem to help with ImageMagick, in my testing.

[hyanwong]

I've just submitted it as a bug to ImageMagick: https://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=36936 . Dunno what you want to do in the meantime, @benjeffery / @jeromekelleher ?

[molpopgen]

Thanks everyone. In the meantime, I'll change my Makefiles to use inkscape.

[hyanwong]

Thanks everyone. In the meantime, I'll change my Makefiles to use inkscape.

If you want, you could use ImageMagick but simply cut out the <![CDATA[ strings. At the risk of incurring the wrath of Pythonistas, this should do it:

perl -pi -e 's/<!\[CDATA\[|\]\]>//g' myfile.svg

🤯

[molpopgen]

"Perl PIE" like that saved my PhD on several occasions!

[benjeffery]

If we have a way that works (inkscape) then add it to the docs and move on I think. Hopefully that bug will be fixed eventually.

[hyanwong]

If we have a way that works (inkscape) then add it to the docs and move on I think. Hopefully that bug will be fixed eventually.

Yep. Also, apparently, ImageMagick should use the Inkscape libs if they are available, so there's probably a way to get ImageMagick to work on @molpopgen 's system.

[molpopgen]

If we have a way that works (inkscape) then add it to the docs and move on I think. Hopefully that bug will be fixed eventually.

Yep. Also, apparently, ImageMagick should use the Inkscape libs if they are available, so there's probably a way to get ImageMagick to work on @molpopgen 's system.

I found something about that when first exploring this, but haven't been able to find it again. In the end, I'll just update the Makefiles in various projects. I'd prefer to use convert, though, as it is a smaller dependency, but oh well.

[grahamgower]

I haven't tried it, but mupdf/mutool convert has added svg support recently (at least it's in the git repo, not sure about any releases).

[molpopgen]

Thanks @grahamgower. Version 1.16.1 does convert svg to png but has the same problem that IM does.