Comment 2 for bug 1778802

Thanks you for your work.
Some comments:
ImageVariable.patch: This I need to check. This is a big change and I want to understand it before committing it.

ImageVariableGroup.patch: This code and similar one is used at several places. Would it also help to inline the getimage function to achieve the same/similar speed improvement?

GreatCircles.patch: Already pushed to repository.

GreatCircles-image.patch: Instead of the workaround (and the same or similar code is used at several places through the whole repository) we should fix the initialization of the SrcPanoImage class. I tried to rewrite the initialization of this class with modern C++. Could you please try if the attached patch brings the same effect?