Ok, here is a procudure that is somewhat in-elegant, but works
:
A. Open the two files, for example 2k x 2k main texture and 256x128 emblem
B. Scale the Emblem to the same size as the main texture or else things will depend on the size of the emblem
C. "Paste into selection". Due to step B one now has a clearly defined situation, both pictures are exactly on top of each other. Obviously GIMP uses the lower right corner as reference. So, this is now at 2048 x 2048.
D. Go into dialog / layers and slide the opaqueness from 100% to say 30%
E. Press Shift T to "scale the layer".
F. Click on one of the 4 corners and move the corner. You will for unknown to me reasons now see three pictures, the main texture, the emblem in complete size and the newly scaled emblem. Without step D the "covering all" emblem could now obstruct the view to the area you want to see. In a nice for us feature, the scaled emblem is not affected by the slider. (Sigh - hard to explain)
G. Until now, you needed to see the complete 2k x 2k, but once you have roughly scaled, you can zoom in with the "+" key and use the scrollbars to focus on the area the emblem is positioned on
H. Move the corners to the final position. There is a dialog "scale" that automatically opene when one clicks on a corner. This now contains the scalefactors in x and y, with 2 digit precision.
I. To find the position, move the cursor over the lower left corner of the emblem "bounding box" and see the corrdinates in the status bar, for example (630, 417) in my case. Together with the complete size of 2k x 2k, one (say a small tool I can write or even bob.exe) can determine the translation in percent.
