SVG file size much larger than expected when using pencil pressure

[akp]

Setup
AD version: 1.6.4.45
Device: iPad Pro 9.7-inch
iOS version: 12.3

Problem
I'm new to digital art and drawing programs, so please bear with me.

I'm working on a project that requires lots of simple drawings that need to be served efficiently on a website. Since these drawings are simple black-on-white line art, I thought SVGs would be a great choice and decided to use Affinity Designer since it supports SVG exports and looks powerful enough to help me manage my project workflow.

I've been surprised to find that even very simple drawings are 2x the file size of their equivalent PNGs and at least 10x larger than I thought they would be. I think this is related to brush pressure, but I'm not sure why, as the strokes I'm making don't have many pressure nodes.

What I've tried
1) New document with program defaults (1024pt x 768 px @ 144 DPI), then Document -> Export
Results: PNG-24 is 13.09 kB, SVG is 460 B. This is roughly what I expect.

2) From (1), draw a long squiggly line with an 8pt "Solid Brush" pencil with the "Brush Defaults" controller.
Results: PNG-24 is 116.33 kB, SVG is 387.17 kB. This is huge!

3) From (2), remove all pressure nodes in the Stroke Studio panel.
Results: PNG-24 is 116.40 kB, SVG is 3.59 kB. This is roughly what I expect.

4) Repeat (2) and (3) on a new layer with the Vector Brush tool, and hide the old layer.
Results: consistent with (2) and (3) above.

Based on the above, it seems like pencil pressure is the issue, but this is really surprising to me because the Stroke Studio pressure view has only 7 nodes (including the first and last nodes).

For what it's worth, I've attached my sample squiggly line below. Note that the SVG is more than 10x the size of the equivalent afdesign file.

Questions

- What are my options for avoiding or mitigating this behavior?
- Why is this happening in the first place?

Thanks in advance!

Untitled.svg

Untitled_1.afdesign

Edited May 26, 2019 by akp

[Callum]

Hi AKP,

Unfortunately this is currently a bug with expand stroke being applied to pressure curves on export. You can see once you reimport the SVG the amount of nodes that has been added to the line is very high. We hope to have this fixed in a future version, sorry for any inconvenience. 

Thanks

Callum