A Tip when using GIMP to create blend masks

#1
I found this quite by accident and after much frustration and posts here and as I had the same problem at a later date and had completely forgot about the initial problem (and how I solved it) I thought it worthy of posting this tip.

When creating BLEND masks using GIMP 2.8

Use a layer with TRANSPARENCY background as normal using a BLACK PEN with a 'hardness' of 25% or 50% (your choice) as normally done to create a nice blending along the edges.

Create a new layer (name it WHITE) with a WHITE background.

Now you need to FLATTEN these two layer which will replace all the transparent areas with WHITE.
I suggest that you temporarily delete all other layers and then select FLATTEN IMAGE from the IMAGE menu.

EXPORT this 'flattened' layer as your BLEND MASK.

If this is not done then you will end up with a two color blend mask which has lost all of the grayscale edges of your mask.
 
#3
I have also found another method since creating this (tip) thread.

I have found that you can achieve the same result as follows -

Select the Mask layer.
Then remove the transparency via LAYERS > TRANSPARENCY > REMOVE ALPHA CHANNEL
When you do this the two tone gray areas (transparency) will be replaced by white.
This is simpler than flattening with a white layer.

I have created a document on how I created both water/land masks and blend masks using GIMP 2.8 and would like to make it available to anyone in case it helps anyone who experiences the same issues that I encountered and also to help users save disk space by creating the smallest mask file sizes possible.
I am not sure how to do that other that just to create a new thread.

Regards
 
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