Figure text contrast on Map notebook repr is very low on dark background

[dstansby]

Describe the bug

The contrast on the figure text is very low against a dark background:

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To Reproduce

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Screenshots

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System Details

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Installation method

No response

[ayshih]

This is really a separate bug, but also the image shouldn't look like that (irrespective of theme). As a histogram-equalized image, it should be using black and dark grays...