In this time of staying at home, we are playing an old school D&D game using Zoom. I have a PDF of a map that I would like to selectively reveal over screenshare (without saving the colour overlay on the file).

Essentially I would like to colour over the map, then manually erase the background overlay. This would be simple to do in Photoshop with the magic eraser, but I can't work out how to do it in Preview and don't have Photoshop.


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Partially revealed

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Completely revealed

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  • 3
    Apple's Preview in not really an image editor beyond sweeping document encompassing edits (i.e. color or tonal adjustments across an entire image). If you need pixel-level editing Preview is not a good tool to try. There are may other free tools out there.
    – Scott
    Apr 1 '20 at 22:32

The image is a raster image, so use a raster image editor. I'd suggest using one that has support for layers. Photoshop is not the only tool available. GIMP is free, and works on Mac, Windows, and Linux.

In GIMP you could create a new transparent layer above the image. Then use the Lasso tool to make a selection, fill it white. Add more layers and repeat.

Then you could hide or reveal the layers as required, and export as PNG/JPEG etc.


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  • Thank you @Billy Kerr I was hoping to get away with using only Preview, but the use of a layer per room is actually a great idea. Perfect! Apr 2 '20 at 6:54

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