Fwd: XProc-based rasterizer

Sorry, in usual fashion I just sent this only to Norm:


---------- Forwarded message ---------
From: Wendell Piez <wapiez@wendellpiez.com>
Date: Fri, Mar 7, 2025 at 3:28 PM
Subject: Re: XProc-based rasterizer
To: Norm Tovey-Walsh <ndw@nwalsh.com>


Hi again,

Recently I was asked what are uses of p:identity. Here is one. As an
alternative to what I just posted:

<p:identity name="svg-file"/>

<p:insert
match="/descendant::fo:instream-foreign-object[@id='svg-placement']"
position="first-child">
    <p:with-input port="insertion" pipe="@svg-file"/>
    <p:with-input port="source">
        <fo:root> ...

Since the SVG is on the main input, the identity allows us to capture that
without having to reference the source port of the pipeline directly.

Question: which one is easier to understand?

Regards, Wendell


On Fri, Mar 7, 2025 at 3:21 PM Wendell Piez <wapiez@wendellpiez.com> wrote:

> Hi,
>
> Thanks Norm and John for comments so far. After reflection, I don't
> actually regard this as a casting problem but a rendering problem, at least
> when inputs are SVG. :-)
>
> In any case since the same host of questions asked by Norm arises also in
> the XSL-FO context, I am exploring that option.
>
> Apparently FOP can be made to do this (i.e., produce PNG), perhaps I can
> get that written to the file system somehow.
>  I am looking at prior art as documented here:
> https://www.oxygenxml.com/pipermail/oxygen-user/2011-June/003664.html
>
> This is what I have so far, with an SVG document on the input port:
>
> <p:insert
> match="/descendant::fo:instream-foreign-object[@id='svg-placement']"
> position="first-child">
>     <p:with-input port="insertion" pipe="source@make-png-from-svg"/>
>     <p:with-input port="source">
>         <fo:root>
>             <fo:layout-master-set>
>                 <fo:simple-page-master master-name="svg"
>                     page-height="{$height}" page-width="{$width}">
>                     <fo:region-body/>
>                 </fo:simple-page-master>
>             </fo:layout-master-set>
>             <fo:page-sequence master-reference="svg">
>                 <fo:flow flow-name="xsl-region-body">
>                     <fo:block>
>                         <fo:instream-foreign-object id="svg-placement"/>
>                     </fo:block>
>                 </fo:flow>
>             </fo:page-sequence>
>         </fo:root>
>     </p:with-input>
> </p:insert>
>
>
> The question will be how to invoke the formatter to do the right thing.
>
> Since I also have some animal bones on the fire (er, beef short ribs in a
> braise), this is as far as I have made it so far today.
>
> If you know already this won't work (even producing a PNG file as a side
> effect), I'll be interested in more details.
>
> Thanks! Wendell
>
>
>
>
>
> On Fri, Mar 7, 2025 at 12:39 PM Norm Tovey-Walsh <ndw@nwalsh.com> wrote:
>
>> John Dziurlaj <john@turnout.rocks> writes:
>> > I'm not sure casting content types would be enough to fully effectuate
>> a cast that is inherently lossy. When casting from a vector to raster
>> image, resolution, color spaces, bit depths, aliasing among other things
>> need to be considered. Such nuances could be handled via option parameters,
>> but those are implementation-defined.
>>
>> I fear even in a rasterize step, some of those are going to be
>> implementation-defined parameters. Different raster formats support
>> different color spaces, may support limited resolutions or bit depths, etc.
>>
>> What would the “general” parameters be, I wonder?
>>
>> - Size
>>   - If width and height are provided, does that change the aspect ratio?
>> - Resolution
>> - Color
>>   - Bit depth? Color space? I’m not even sure what the options are
>>
>> > There is also the question of which set of casts are supported by a
>> given XProc processor. Built for purpose steps on the other hand give a
>> clear contract as to which functionalities are available and which aren't.
>>
>> I agree. I think a step is the better answer here.
>>
>>                                         Be seeing you,
>>                                           norm
>>
>> --
>> Norm Tovey-Walsh <ndw@nwalsh.com>
>> https://norm.tovey-walsh.com/
>>
>> > The one serious conviction that a man should have is that nothing is to
>> > be taken too seriously.--Nicholas Butler
>>
>
>
> --
> ...Wendell Piez... ...wendell -at- nist -dot- gov...
> ...wendellpiez.com... ...pellucidliterature.org... ...pausepress.org...
> ...github.com/wendellpiez... ...gitlab.coko.foundation/wendell...
>


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