SVG/PNG export does not preserve axis/tick font settings and clips axis label #4388

Current behavior

When exporting a spectrum as SVG or PNG, the exported figure does not preserve the font settings used in the NMRium display.

This may be related to #3529, which concerns customization of font size and font family. In the current UI, these settings affect the on-screen spectrum, but they are not reproduced correctly in the exported figure.

Observed behavior:

• Tick-label font size in the exported image differs from the size shown/configured in NMRium.
• Axis-label font size is not preserved.
• The font family changes during export.
• The x-axis label (δ [ppm]) extends beyond the image boundary and is partially clipped.
• The problem occurs with both SVG and PNG export.

Steps to reproduce

1. Open a 1D spectrum.
2. Change the axis/tick-label font settings.
3. Confirm that the new settings are visible in the NMRium display.
4. Export the spectrum as SVG or PNG.
5. Compare the exported figure with the on-screen spectrum.

Expected behavior

• SVG/PNG export should preserve the configured font size and font family for axis and tick labels.
• The exported figure should visually match the spectrum shown in NMRium.
• Axis labels should remain fully inside the exported image frame.

Screenshots

NMRium display

The configured axis and tick-label font settings are visible in the NMRium interface.

Exported PNG

The exported figure uses different font sizing/font rendering, and the x-axis label is clipped at the bottom.

Related issue

• Customize font size, color, ... #3529 — Customize font size, color, ...