when using the img plugin with an svg file, it is supposed to convert it into a png for display in all browsers, and because the typical use case is rendering small preview versions.

this currently doesn't work (at least with graphicsmagick-libmagick-dev-compat 1.3.18-1) due to the sequence imagemagick options are set, needs an extension to work for pdfs (or any other imagemagick compatibile file) too, and should have an additional parameter for page selection.

i've provided a series of patches in the chrysn/imgforpdf git branch.

i'd prefer to go a step further, and not only convert pdf and svg files to png, but everything (with the possible exception of jpg files), as most other image formats can't be displayed in a browser anyway -- but i didn't in this patch series, as it would alter the file names of existing images, i don't know if that needs special care or breaks something i don't use; this way, my patches should be safe for inclusion.

--chrysn

update 2014-06-29: the patch still applies and fixes the issue. in the meantime, i noticed that the desired effect doesn't happen when no explicit size is set. as scalable graphics don't necessarily have a natural size anyway, i don't consider that a showstopper. --chrysn

This all looks good in principle, but I would like to do a more detailed review, and test it with "real ImageMagick" in case its behaviour differs from GraphicsMagick.

An automated regression test for the desired behaviour in t/ would be great. There are SVGs and PNGs in the docwiki already; there are no JPEGs or PDFs, but perhaps you could add a trivially small example of each to t/? Imitating t/tag.t or t/trail.t, and skipping the test if the required modules are missing like t/podcast.t does, seems like it would work best.

I agree that everything not in an interoperable web format should be converted to PNG when it's scaled down, but yes, that's more likely to be a breaking change, so it seems best to do that as a separate branch. In practice I think this means JPEG -> JPEG and everything else -> PNG, since JPEG is commonly used for photos and photo-like images that don't compress well under lossless compression. --smcv

i've added a unit test and tested it with the [[!debsid perlmagick]] package, the [[!debsid graphicsmagick-libmagick-dev-compat]] package and the experimental libimage-magick-perl package (where the libmagickcore-6.q16-2-extra package is required too), in the meantime filing Debian bug #753770. (why is it that it sometime seems i find more bugs in ikiwiki's dependencies than in itself when working with it?)

the unit test also checks for file removal when it is not created any more, which works, so my biggest fear about the all-to-png change is unwarranted. i'll have a look at that some time, but i think as things are, this is ready now, please review again. --chrysn

merged --smcv