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I am trying to georeference a rather large PDF. I was successful in doing so without compression.

However, when trying to make the map lighter, I added some compression. The options are: LWZ, PACKBITS, and DEFLATE. No matter which one I use, the output resolution is very low. The partial solution is checking Set target resolution, but still it only goes so far (1, -1), the output is pixeled and the labels on the old map I'm trying to georeference cannot be read.

I know this problem could be solved if I transform the pdfs into images and pre-resize them. But I'm looking for a more integrated solution. Is there a way to define the target resolution differently?

My setup:

QGIS: 3.10.10-A Coruña,

GDAL: 3.0.4, Win 10, FullHD laptop + 4K display.

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  • Additional info: The size of georeferenced files is: 75 MB for uncompressed, 500 kB for compressed without target resolution set and 6,5 MB for compressed with target resolution 1,-1. If judging by the quality, I would like to get something between 15 and 20 MB, should be good enough. – Matos4df Jan 12 at 11:10
  • It is probably possible just to add the georeferencing into PDF without touching it otherwise. That should keep the original quality and file size. However, I do not know exactly how to do it. I believe that "neatline" deals with that gdal.org/drivers/raster/pdf.html#raster-pdf. – user30184 Jan 12 at 11:58
  • Compression won't affect your resolution – Ian Turton♦ Jan 12 at 12:35

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