Simple Tile blend/mask software?

Simple Tile blend/mask software?

I am working on a simple social 3/4 view game. Just about everything I need is already coded.

 

I need to make tiles for terrain. All I need done is a simple task. I want to take the two attached textures and get a tile set generated as shown in the diagram (excluding the outer tiles because those would come from one base texture.) Once that is done, I'll re-size and insert myself into the game.

 

Does any software exist that will do that simple task of taking texture A and texture B, and making a tileset shown in image C, and only does exactly that?

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Lavabowl.png Lavabowl.png 146.8 Kb [22 download(s)]
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Mountainrock.png Mountainrock.png 191.1 Kb [15 download(s)]
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essay-tiles-709315.jpg essay-tiles-709315.jpg 21.5 Kb [14 download(s)]