Hi Gary,
I couldn't keep you (and especially myself) in suspense anymore.
I compiled using my NEW water and blend TIF masks and fired up FSX.
IT WORKS!! Nice blending too.
Well we have both leaned something new. I just knew there had to be an answer BUT what I just don't understand is how those other authors (of photo realistic tutorials using GIMP) got their scenery to work.
Mind you my new BGL is slightly larger than the one created using BMP masks even though the actual water and blend TIF mask filesizes are smaller than the BMP ones.
Now for the work flow again using GIMP (ADDED LATER) I just noticed that you didn't request my work flow but as I had already typed it in I have left it there below.
Open the background (satellite image file created with SBuilderX) with GIMP (which opens the file and automatically creates a 'background' layer.
Add a new layer (right click in the 'layers' window) and enter WATER MASK as the 'Layer Name' and select TRANSPARENCY FILL TYPE of TRANSPARENCY and click OK
Add a new layer and enter BLEND MASK as the 'layer name' and select TRANSPARENCY FILL TYPE of TRANSPARENCY and click OK
Add a new layer and enter WHITE MASK as the 'layer name' and select TRANSPARENCY FILL TYPE of WHITE and click OK. This will be used later to replace the transparent parts of the water and blend mask with color white.
I suggest that you SAVE your work before continuing just in case you accidentally make a mistake with any of the masks.
LOCK all layers except the WATER MASK layer (left mouse click on the area next to WATER MASK under the 'lock' icon which looks like a paint brush. An icon which looks like a link in a chain will appear.
Make sure the BACKGROUND image layer (the filename of the satellite image you opened with) is displayed (click on the area to the left of that layer - an icon looking like an eye will appear)
Do the same for the WATER MASK layer
Make sure no other layer is selected to display.
Select paint brush tool and color BLACK with OPACITY set to to 100 and BRUSH set to 100
Ensure the WATER MASK is selected (left click on it) and also the BACKGROUND image (the filename of the satellite image you opened with)
Make sure the BACKGROUND image layer (the filename of the satellite image you opened with) is displayed (click on the area to the left of that layer - an icon looking like an eye will appear)
Do the same for the WATER layer
Make sure no other layer is selected to display.
Paint out all the areas of water
LOCK the WATER MASK layer and UNLOCK the BLEND MASK layer.
Select paint brush tool and color BLACK with OPACITY set to 100 and BRUSH set to 25 or 50. This will result in a nice blending between the parts of the satellite image you want to show through and the default FSX scenery texture.
Ensure the WATER MASK is selected (left click on it) and also the BACKGROUND image (the filename of the satellite image you opened with)
Make sure the BACKGROUND image layer (the filename of the satellite image you opened with) is displayed (click on the area to the left of that layer - an icon looking like an eye will appear)
Do the same for the BLEND layer
Make sure no other layer is selected to display.
Paint out all the areas you don't want showing in FSX
Now comes the time to create MASK image files.
DELETE all layers except the ones named WATER MASK and WHITE MASK (this does not actually delete them unless you click on SAVE so don't do that)
Now FLATTEN the two layers into one - select FLATTEN IMAGE from the IMAGE drop down menu.
You will now only have one layer displayed and all the area of transparency will be replaced with the color WHITE.
EXPORT the image as a TIF image (select EXPORT AS from the FILE drop down menu)
Type in a filename and ensure TIF is selected as output (SELECT FILE TYPE)
You will now have to UNDO all FLATTEN IMAGE and all the DELETE LAYER steps you previously did by clicking on UNDO FLATTEN IMAGE from the EDIT drop down menu and then clicking on UNDO DELETE LAYER from the EDIT drop down menu until all the layers you previously deleted are restored.
Now do the same for the BLEND MASK. DO everything the same as you did to create the water mask file but selecting BLEND instead of WATER.