[NTG-context] Radial and linear gradients

[Thangalin]

Inkscape can export the gradients to PDF.

I was hoping to eliminate Inkscape as an extra piece of software users
have to download to make sure their SVG images are rendered correctly.
By containerizing ConTeXt, MetaPost can be swapped for Inkscape, so
users won't even know. It is, however, a minor duplication to have two
programs that can convert SVG to PDF. (And Inkscape will bloat the
container size.)

For my images, at least, gradients are one of the last features needed
to render them correctly using MetaPost. The other is font rendering
in some cases will be incorrect (e.g., try using Roboto with weight
100). If we have to use Inkscape to ensure tat all SVG images are
rendered correctly, then we'd only want to use MetaPost if we know
that the images don't contain gradients, or would you recommend
avoiding MetaPost altogether for SVG conversion?

Thank you!

On Wed, Dec 14, 2022 at 12:46 AM Hans Hagen via ntg-context
<ntg-context at ntg.nl> wrote:
>
> On 12/14/2022 5:46 AM, Thangalin via ntg-context wrote:
> > Hi there!
> >
> > Any thoughts on implementing SVG gradients in MetaPost?
> >
> > % SOF
> > \startbuffer[csvg]
> > <svg xmlns="http://www.w3.org/2000/svg"
> > xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 115.669
> > 115.669"><defs><radialGradient xlink:href="#a" id="b" cx="124.515"
> > cy="167.114" r="57.834" fx="124.515" fy="167.114"
> > gradientTransform="translate(-17.77 -18.4)"
> > gradientUnits="userSpaceOnUse"/><linearGradient id="a"><stop
> > offset="0"/><stop offset="1"
> > stop-opacity="0"/></linearGradient></defs><g
> > transform="translate(-48.91 -90.879)"><path fill="red"
> > fill-opacity=".5" d="M48.769 90.936H164.64V206.96H48.769z"/><circle
> > cx="106.745" cy="148.713" r="57.834" fill="url(#b)"
> > fill-rule="evenodd"/></g></svg>
> > \stopbuffer
> >
> > \starttext
> >    \placefigure{}{\includesvgbuffer[csvg][conversion=mp]}
> > \stoptext
> > % EOF
> >
> > See attached a comparison of the PDF generated using ConTeXt and the
> > PNG file generated by exporting from Inkscape.
> these gradients definitions get crazier by the day ... does inkscape
> output a bitmap or vector pdf
>
> given what we do with context i'm not sure we should support everything
> that pops up (mapping all onto mp and then pdf ...)
>
> Hans
>
> -----------------------------------------------------------------
>                                            Hans Hagen | PRAGMA ADE
>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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