Layering Images and using a transparency brush

[Urqy]

Is there a way to layer two images (maps) and then use a "transparency" brush on the top image to partially reveal the lower image?

As an example use the the DM map and player map of Chult with the player map on top of the DM map. As the players explore inland away from the coast you use the transparency brush to "reveal" what they find below.

I am hoping to use this in Fallout home brew with a 50's style map the players find in a gas station layered on top of another map that reflects the world they've discovered. They won't know where they are when they exit the vault.

[SilentRuin]

Typically I do that with layers. For example I'll create on painting layer for some background stuff in an old dungeon and then overlay another layer with a dusty image of just dirt which I'll set the Alpha of that (transparency) to a point where it makes the layer under it appear dusty since it can be seen through the dust layer. Order of those painting layers is important - top is the last one placed (over all the others below).

Not sure that helps but that is how I handle transparency issues in my image. Layers.

Then if you want - you can have two solid objects in two layers and turn them both on for everyone - then turn the top one off (invisible) when you do the reveal.

[Urqy]

Thanks for the reply @SilentRuin. I really only wanted to partially reveal the underlying map a little at a time as they explore. Someone else suggested using a variant of your last sentence with the top layer made of many smaller tiles to cover the map that can be turned off to reveal only a portion of the map below. I'll give that a shot. Thanks again.

[SilentRuin]

Thanks for the reply @SilentRuin. I really only wanted to partially reveal the underlying map a little at a time as they explore. Someone else suggested using a variant of your last sentence with the top layer made of many smaller tiles to cover the map that can be turned off to reveal only a portion of the map below. I'll give that a shot. Thanks again.

There is also outright masking - that is just black completely though until you unmask that area.