Tikz images for PreTeXt

[Alex-Jordan]

The "PTX" display mode is only used when someone is doing a one-time processing of their PreTeXt book project. Whereas the HTML output might print <img src="aliased.svg"/>, the PTX output would be <image source="aliased.svg"/> and part of the PreTeXt WeBWorK processing script would (a) store all that output in a local file and (b) download and store aliased.svg from the server's webwork_files folder.

When the display mode is "PTX", it would be ideal if multiple image file formats would be created and stored with the same alias prefix. The PTX output could perhaps just be <img src="aliased"/> and then the PreTeXt script would locally store several files: aliased.svg, aliased.png, aliased.pdf, and even aliased.tex.

I have a few questions. (1) For anyone familiar with how the aliasing works: will it be easy to store the various image files to have the same aliased prefix even with different extensions? So if I produce image.png and image.svg, and image.png gets aliased as foo_bar.png; will I have a tough time getting image.svg to alias as foo_bar.svg?

My other question might be moot if the answer to (1) is discouraging.

(2) The code in TikzImage.pm assumes that there is only one final image file. For PTX output I would like there to be several. I can think of two general outlines for how I would modify that code. One would be like:

if we are making images for PTX {
   do lots of things
} else {
   do all the things that are currently done
}

Pro: that would make the code easy to review. Con: that is not a good approach if there is any reason to believe that producing multiple image formats might be useful for something other than PreTeXt. The alternative is more like visiting each possible image output type one at a time and asking if we need to make it.

always make the .tex
if we need to make .pdf, make it
if we need to make .dvi, make it
if we need to make .png, make it
...

The conditional tests might be like if ($ext eq 'png' || $ext eq 'PTX').
The only pro would be it sets the code up for other display modes that might want multiple image formats. Con: the current code will need significant restructuring.

Asssuming I can get past issue (1), I'm on the fence with (2) and I would go in whatever direction anyone has a preference for.

[drgrice1]

The filename returned by PGalias->make_resource_object does depend on the extension. So asking for a resource object with the png extension and another with the svg extension would give different file names. However, you could just ask for a single alias, and use that for both (or all) images. The extension would make the filename different in any case. If you are using the PGtikz.pl macro, you could just change the extension (via $image->ext) and that would not change the filename since that is set initially when the TikZImage object is created, and does not change when the extension is changed.

I am not sure that you could make TikZImage produce multiple images on one run. At least not without massive restructuring of the entire setup. Currently the draw method of the TikZImage is called by insertGraph which expects data for a single image (not a file). insertGraph writes that data to a file.

[Alex-Jordan]

I am not sure that you could make TikZImage produce multiple images on one run. At least not without massive restructuring of the entire setup. Currently the draw method of the TikZImage is called by insertGraph which expects data for a single image (not a file). insertGraph writes that data to a file.

Thanks, that is the kind of understanding that I was hoping for.

Well, since this is essentially for one-time processing by PreTeXt, it is not so bad if a problem with a tikz image gets run multiple times to get the various formats back.

Any objection to me adding tex as an extension option? Just an additional thing PreTeXt likes to collect.

[Alex-Jordan]

I believe I have something working such that in addition to the current supported file extensions, you can have 'tgz' as a file extension. This makes the link from insertGraph be a tgz file containing the thing PreTeXt wants: tex, pdf, svg, png.

I have some cleaning up to do before I post it for review. Does it raise any flags to treat tgz as an image format? This would only be used for PTX support. Similarly to when the display mode is hardcopy and 'pdf' is forced as the extension, when the display mode is PTX, 'tgz' would be forced as the extension.

[drgrice1]

There is no need for the data that is returned by the draw subroutine to represent an image. Whatever it returns, the insertGraph subroutine will write to disk. In fact the answerDiscussion.pl macro uses this to write its data in text format to disk.