Last time in this series I talked about my experiments in testing whether Gimp could handle a large canvas size successfully, since this would tend to suggest a linear project for covering a long section of rail corridor (17 km in a current project) could work. If successful this might be a better way of covering maps for a long suburban track area compared to overlaying the sections in a smaller canvas.
Well I took Gimp up to 11x7 and then up to a much larger 17x10 size to test this idea. However this is the point where Gimp couldn't handle the large canvas size. A save operation having repositioned layers but not added any new ones, saw the file saved to the exact same size as its predecessor, and then when refreshing the project after save, as generally happens, Gimp crashed after having exhausted the tile cache. This should have been taken up by its swap onto the home drive, but for some reason that didn't occur.
So I currently have my project in the last stable save at 11x7 and will be taking it back to 7x7. Therefore the overlaying of different layers is the only way to produce maps for multiple different areas in a single file. The organisation of these files means you are scrolling through 149 layers in the layer list. Gimp has layer groups that should do the job, but in fact consume additional resources that slow everything down.
At a guess the canvas size aspect is because Gimp has to resource the complete canvas, regardless of how much of its area is used or not. I am picking the resource use will be a complete canvas, and then individual layers referenced to an area of the canvas. Hence using a smaller canvas is more efficient where there are multiple layers that can share the same area of the canvas. This is a design aspect of the software in that it has to maintain the resources to draw every part of the canvas even those parts that aren't being used.
I'm still rapt with what I can do with Gimp and how I can make this all work for my maps projects, yet also see some limitations of Gimp design. Gimp is a great piece of open source software and hopefully it might be possible to address the layer groups issue in a future revision.
