We are trying to develop a workflow to generate .mbtiles (for offline tiled map viewing) from a QGIS project.
A few years back, in QGIS 2.4, we went with QGIS -> multiple tiffs -> multiple GeoTIFFs -> VRT -> tiles. That introduced some image quality loss. See that question here.
Even back then, it seemed the real way to get around image quality loss would be to use QGIS server and download the tiles that it serves up. It was over my head and I did not make any attempts along those lines.
Now, QGIS 3.4 serves WMTS so the serve-and-download method seems to be more feasible. I set up WAMPServer (Windows 10) and QGIS Server (3.4), and I am getting pretty close but am not having luck finding a good way to grab all the tiles served up by QGIS server.
I can grab the entire map image of a simple locally-served map using WMS:
I can grab one tile using WMTS:
(At the moment, that is serving up a solid black 256x256 image even though the full WMS map looks correct with a few town boundaries, but, I will figure that out separately.)
What's the best way to grab a full tile set or mbtiles file based on the WMTS single-tile request above?