PNG export from light theme always appears as dark theme (Gantt chart)

[chinyaolin]

Title: PNG export from light theme always appears as dark theme (Gantt chart)

Description:
When using Mermaid Live Editor in light / default theme, everything looks correct in the editor preview. However, when exporting a Gantt chart to PNG via "Download PNG", the output image is rendered in dark theme (dark background, light text), ignoring the selected light theme or any explicit theme override.

Steps to reproduce:

1. Open Mermaid Live Editor (e.g. https://mermaid-js.github.io/mermaid-live-editor/)
2. Select light/default theme
3. Paste a Gantt chart mermaid snippet, for example:

gantt
    title A Gantt Diagram
    dateFormat  YYYY-MM-DD
    section Section
    A task           :a1, 2014-01-01, 30d
    Another task     :after a1  , 20d
    section Another
    Task in sec      :2014-01-12  , 12d
    another task      : 24d

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[chinyaolin]

The attached screenshot shows the result when I choose to export as PNG.

[ning-bao]

Same issue here... Seems fine with svg export, have tried editing the themes but seems changing themes aren't helping.

[chinyaolin]

I was able to get a correct PNG image with the following steps, which might help others:

1. Export the diagram as SVG.
2. Open the SVG in Microsoft Edge, and use the Export SVG plug-in to export it as PNG.
3. The exported PNG will have a transparent background, but the other colors are correct.
4. Open the PNG file in Photopea.
5. Add a solid white layer at the bottom, then save the PNG again

— now the colors display correctly.