Creating set of maps (PDF) using QGIS and Python with WMS Data

Question

For a scientific project I am trying to create a set of PDFs in QGIS with a fix layout (in the print composer) but per PDF a) different map item attributes (extents) and b) a QR-code to identify this PDF. The QR-Codes are already created with a python module (-> .svg) and the extents of the map items are a simple raster. The map content is a WMS which is embedded in the QGIS project.

My idea is to open a pre-defined print composer, iterate through the raster (has simple coordinates) and generate a PDF per iteration with the actual a) map layout and b) QR-code.

I am working with QGIS 2.12.1 (uses Pyton 2.7.5)

Answer 1

Finally I created the PDFs with the atlas plugin in the print composer of QGIS. In the atlas configuration I set my shapefile as covering layer and used a dynamic expression for the filename like

'Map_'|| x_min(@atlas_geometry) || '_' || y_min(@atlas_geometry) || '_' || "SCALE"

The QR-Codes I generated before are shown as an image with an also dynamic expression, in this form

to_string( 'C:\\......\\' || x_min( @atlas_geometry ) || '_'|| y_min( @atlas_geometry ) || '_5000.svg')

for the scale 1:5000. Both worked pretty fine and took its time (about 3 days for the 20'000 maps). Actually my problem is: The printed WMS data (especially the fonts) are too small, the output (PDF or image) doesn't look like the preview in the print composer (see 2 screenshots). I just used the "export to pdf" function without chaning any settings. How can I get the output scaled like in the preview?