Hi Regis, I would assume that in this use case the user would not be modifying the source polygons, but would make a copy of them which could be a memory layer and then resize them. I mentioned resizing small features so that they visibly would be better shown on the map, but the other use case would be when the user draws a polygon and would then like to shrink or enlarge it, then perhaps move it into position. QGIS already has the move tool, but I don't see one to shrink or enlarge polygon tool.
I understand how a point label's size can be modified based on some attribute, but can an expression be written that would allow a polygon size be scaled and centered about the source centroid, based on some attribute in the data. If that is possible I don't know how it would be done. Thanks, Calvin On Wed, Feb 22, 2017 at 2:53 AM, Régis Haubourg <[email protected]> wrote: > Hi Calvin, > what you describe requires to store the specific object size somewhere, > which is the exact same requirement with data defined labeling (or any data > defined stuff in QGIS, those widgets are everywhere). > Modifying the source layer is quite wrong, and sometimes impossible > (readonly datasets). You can have a look to EasyCustomLabeling where I > coded a duplication of the objects I needed to label into a memory layer. > Persistence is made thanks to MemoryLayerSaver plugin that saves them in a > separated .mldata file. In you case, a symbol is made of so much markers, > sub markers that you can't just define one width or size parameter shortcut > button (or mouse scroll + key modifier) so easily. > > This is anyway quite hacky and justify a planned and funded work for QGIS3 > : Auxiliary storage. That work will provide a way to store data or other > ressources inside the qgs project. That will provide a nicer and more > portable method for custom labeling or styling. > > Just to end up with your cartographic need, up to now, I've always managed > to handle what you describe with conditional rules in expressions without > having to manually storing values. I eventually had to store exceptions to > rules in the following way: > > Ex: Styling city point with size proportional to the number of inhabitants > , except for one > > CASE > WHEN city = 'Grenoble' then 22 > ELSE scale_exp("altitude", 0, 0, 1, 10, 0.5) > END > > I hope that helps > Cheers Régis > > 2017-02-21 21:14 GMT+01:00 C Hamilton <[email protected]>: > >> I have an project where I want a feature to be larger than life just so >> that it shows up on the map. Ideally I would like is to be able to select >> one of more features and with the mouse have it interactively resize them, >> but keeping them centered about their centroids. Once I am satisfied with >> their size I would either click a button to fix them or hit the Enter key. >> >> I saw the Affine transformations plugin, but that takes too much thought. >> Is this capability already there and am just not finding it or has it >> simply not been done? If the latter is the case I may consider writing the >> plugin to do it although I think it would be nice for it to be a part of >> the standard QGIS editing functions. >> >> Thanks, >> >> Calvin >> >> _______________________________________________ >> Qgis-developer mailing list >> [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer >> > >
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