svg->png fails with inkscape and fallbacks to default renderer (only in python)

[subutchik]

I recently changed debian machine and forgot to log how i got it working, but now with wand library it fails to convert svg to png, though on windows it doesn't.

When using convert it does work on debian
Maybe you know what quirk i need to resolve? I remember it wasn't that hard, i edited delegates.xml or/and installed some packages at max.

SVG:

Code:

from wand.image import Image
from io import BytesIO

svg = open('fig.svg', 'rb').read()

with Image(file=BytesIO(svg), format='svg') as img:
	img.format = 'png'
	img.resize(1000, 500, filter = 'lanczos')
	img.quantize(64, colorspace_type = 'srgb')
	img.strip()
	img.save(filename='fig.png')

ImageMagick 7.1.2-8, Inkscape 1.4.2

Console output:
** (inkscape:2579): WARNING **: 13:14:09.132: Failed to wrap object of type 'PangoFT2FontMap'. Hint: this error is commonly caused by failing to call a library init() function.

** (inkscape:2579): WARNING **: 13:14:09.251: Can't open file: /tmp/magick-6bCpVXeGT4yNAOO6t1DEBBjnjzSgrTNh (doesn't exist)

** (inkscape:2579): WARNING **: 13:14:09.251: Could not detect file format. Tried to open it as an SVG anyway but this also failed.

** (inkscape:2579): WARNING **: 13:14:09.251: Can't open file: /tmp/magick-6bCpVXeGT4yNAOO6t1DEBBjnjzSgrTNh (doesn't exist)
ink_file_open: '/tmp/magick-6bCpVXeGT4yNAOO6t1DEBBjnjzSgrTNh' cannot be opened!
InkscapeApplication::document_open: Failed to open: /tmp/magick-6bCpVXeGT4yNAOO6t1DEBBjnjzSgrTNh
ConcreteInkscapeApplication::on_open: failed to create document!

RSVG output (if needed):
rsvg-convert version 2.61.3

libraries used:
cairo 1.18.4
pango 1.56.3
harfbuzz 12.1.0
fontconfig 2.15.0

Delegates:

  <delegate decode="svg" command="&apos;rsvg-convert&apos; --dpi-x %x --dpi-y %y -o &apos;%o&apos; &apos;%i&apos;"/>
  <!-- Change export-filename to export-png for inkscape < 1.0 -->
  <delegate decode="svg:decode" stealth="True" command="&quot;inkscape&quot; &quot;%s&quot; &quot;--export-filename=%s&quot; &quot;--export-dpi=%s&quot; &quot;--export-background=%s&quot; &quot;--export-backgro>  <delegate decode="tiff" encode="text" command="&apos;tesseract&apos; &apos;%i&apos; &apos;%u&apos;; /bin/mv &apos;%u.txt&apos; &apos;%o&apos;"/>

[emcconville]

Thanks for reporting this. Can you try using the latest master branch? A possible fix for #675 should resolve reading with BytesIO buffer.

[Sputchik]

I fear that's not it, i tried both, and i got it working on pypi version on previous debian instance

[Sputchik]

Yes when using in memory buffer magick has some issues with temp file

[Sputchik]

I just can't let it go how i managed to make it work man that's the worst thing ever

[emcconville]

I'll need to dig into this more, but it looks like reading Blobs for SVG are not being written to disk for Inkscape to decode.
This might be an i/o issue with Inkscape, or ImageMagick. Using ImageMagick directly also produces the same WARNINGS

cat fig.svg | magick svg:- fig.png

As for Wand....

The BytesIO is not a subclass of FileIO, and so Wand just copies the content to a blob, and passes it off to MagickReadImageBlob. Roughly the equivalent of...

svg_blob1 = open('fig.svg', 'rb').read()
svg_blob2 = BytesIO(svg_blob1).read()
with Image(blob=svg_blob2, format='svg') as img:

... not efficient, but a good fallback for i/o-like objects.

I know it's not ideal to rewrite a working solution, but perhaps writing the buffer to a temporary file might be needed. Something like...

from tempfile import TemporaryFile

svg = open('fig.svg', 'rb').read()
buffer = BytesIO(svg)

with TemporaryFile('w+b') as tf:
    tf.write(buffer.read())
    tf.seek(0)
    with Image(file=tf, format='svg') as img:
        # ....