Fix filtering artifact for non-color images

[emilk]

Problem: we apply filtering before we apply the color map. This means large changes in depth images produce unexpected colors when interpolating. A similar problem occurs for label maps.

Solution: use nearest filtering for depth images and label maps.

An alternative solution is to apply the color maps before filtering, but that is far more expensive, and likely not worth it.

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[nikolausWest]

nearest filtering for depth images and label maps

Seems like the best approach for these either way