[Qgis-user] Output to pdf file doesn't contain vector details

Tue Sep 19 22:09:45 PDT 2023

In addition to the free resource, I can highly recommend the two books “QGIS Map Design” [1] and “QGIS Map Design - Second Edition” [2] by Anita Graser and Gretchen N. Peterson with tons of great map designs and how to create them. They base on somewhat dated QGIS versions by now, but the content itself is still super valuable.

[1] https://locatepress.com/book/qmd
[2] https://locatepress.com/book/qmd2
Von: QGIS-User <qgis-user-bounces at lists.osgeo.org> Im Auftrag von Emma Hain via QGIS-User
Gesendet: Mittwoch, 20. September 2023 04:11
An: chris hermansen <clhermansen at gmail.com>
Cc: qgis-user at lists.osgeo.org
Betreff: Re: [Qgis-user] Output to pdf file doesn't contain vector details

Michael and list,

But, it should also be possible to use Qgis to (say) input GIS data files in one format (such as NASA's SRTM “tiles”), then output the data in another vector-graphics format (such as .shp shapefiles or .svg files) – for directing the data to another application for further processing, as convenient – whether or not Qgis technically can do much the same further processing.
This can be done by undertaking transformations. In the Processing tools panel, type in the search bar  'convert' and select the appropriate tool - however if you are unsure of what you are doing, you may introduce positional and other errors. By sticking with the cartographic process within QGIS and importing in your other elements, this would produce a more accurate response. I would also really learn about Coordinate Reference Systems (CRS) as well. A map is different to a graphic is you are placing disparate datasets together.

I would totally support learning about the strengths of the cartography of QGIS. It is developed by people who love the art of cartography so perhaps you should harness this? I do understand though that you work with what you have the most experience with.

However, if you do want to go down the path of using QGIS' cartographic power, here are some really helpful online free tutorials: https://www.qgistutorials.com/en/

If you would like additional features in QGIS, please feel free to add them to here <https://github.com/qgis/QGIS/issues> and label them as a feature enhancement.

Good luck
Em

On Tue, 19 Sept 2023 at 03:32, chris hermansen via QGIS-User <qgis-user at lists.osgeo.org<mailto:qgis-user at lists.osgeo.org>> wrote:
Michael and list,

I've been following along trying some stuff with data I have on hand and offer you some comments below.

On Mon, Sep 18, 2023 at 9:25 AM Michael McNeil <memcneil02 at gmail.com<mailto:memcneil02 at gmail.com>> wrote:
The foregoing got sent before it was ready, sorry. I'll just continue from where I left off.

As I said, I would prefer to use shapefiles to transfer the data – that is intended to be an interim format – however CorelDraw doesn't accept shapefiles (.shp) , though it does svg. But I've found that the reason why I can't produce svg (and pdf) files containing the detailed vector-graphics data that I wish to include in the map, for transfer into CorelDraw, is because Qgis believes (so I surmise) that I must want to ultimately print out the data – and because printers (or engravers, or whatever) inherently must have a maximum resolution they can render, Qgis has thoughtfully determined that that maximum should be no greater than 3000 dpi (with a mere 300 dpi being the default).

That, of course (the Export Resolution), is why my detailed contour lines are being rendered (upon Layout) into mere solid blobs of color – accompanied by an 80 MB pdf file! It seems crazy to me.

Not sure you're correct here - did you select "Always export as vectors" in the SVG (or PDF) export window?  If so, then your vectors are not being rasterized.  However, they ARE being reproduced at the thickness determined by your settings and the print scale.

Why? Because – regardless of the merits of being able to transfer full-resolution vector graphics using the svg and pdf formats – there's also the possibility (which the powers at be at Qgis don't seem to realize – I'm sure you all will correct me on this) of using (say) pdf format as a presentation medium for Qgis' (and others') vector-graphics maps. By presentation I mean an interactive experience for viewing maps – in other words, the Qgis output should not just be for printout.

[examples deleted]

The SVG conversion you are using is part of the QGIS "print layout manager" functionality, where the user is preparing a cartographic product for reproduction at a certain scale and resolution.  So it's quite reasonable that such functionality would behave the way QGIS doe; someone using QGIS to make a cartographic product they intend to be used at a print size of 8.5 X 11 inches or 1 X 2 metres would expect to see lines of a chosen thickness when the product is reproduced at that desired scale.

Accordingly, one thing that might help is if you choose a larger page size, the default being A4 or US Letter.  You might also try experimenting with layer Properties > Symbology > Stroke width.  This won't give you the "infinite zoom" you hope for, but the lines will appear finer when zoomed out to full screen and zoomed in to 100% zoom, assuming you selected a fine stroke width.

I can understand your idea that SVG does after all mean "Scalable", but it seems to me that the incorporation of the SVG export into the QGIS print layout manager is not going to go in the direction you want.

You may be able to edit the line parameters in the SVG file once you import it into Corel Draw.  I tried using LibreOffice Draw; I first ungrouped all the elements in the SVG, selected some lines and then edited the line styles.  This produced an SVG with nice thin zoomable lines.

If that had been a map of (say) southern Great Britain (about 300 miles wide), a 6400% zoom would bring you up on any given 5 mile stretch of the map. Nor does a limit of 64x zoom appear to be inherent in the pdf format – it's merely the viewer app designer's option, best I can tell.

Not sure what viewer app you're referring to here so I'll skip over this.

Why wouldn't anybody (Qgis, for instance) want the capability of producing output maps that one can do that with – if desired by the map's creator! Why choose to enforce pixelation onto a vector format where it isn't inherent?

As I mentioned above, you're able to not rasterize, and if you do so, your line thickness is a result of your output settings including line "weight" and page size, ie intended print resolution, not pixelation.

Maybe you should look at a different QGIS export pathway, which you can find by right-clicking on the layer you want to export, selecting  "Export > Save Features As..." and working with whatever format that appears in that list that works with Corel Draw (maybe AutoCAD DXF?).

I suggest that that a specific Export Resolution dpi value in Qgis' Layout settings be made optional – with “Unlimited” as another option.

If SVG were one of the layer export options, I imagine it would be intended to work this way.

Best,
Michael McNeil

On Mon, Sep 18, 2023 at 8:43 AM Michael McNeil <memcneil02 at gmail.com<mailto:memcneil02 at gmail.com>> wrote:
Chris, Garth, others,

Now that we've resolved the issue of reentering Qgis and accessing my previously saved project data (thanks again, Garth!), I can go on to investigate whether Qgis can serve as my entire graphics toolkit for working on and producing the final output version of maps. I certainly wouldn't mind that being the case (even though powerful vector-graphics tools such as CorelDraw also have their place, I maintain).

Shapefiles

But, it should also be possible to use Qgis to (say) input GIS data files in one format (such as NASA's SRTM “tiles”), then output the data in another vector-graphics format (such as .shp shapefiles or .svg files) – for directing the data to another application for further processing, as convenient – whether or not Qgis technically can do much the same further processing.

In this regard, I generated shapefiles corresponding to the input SRTM data, but I encountered 2 problems there: First, my preferred secondary application CorelDraw does not accept .shp (and associated files) input – though it does read .svg and .pdf files.

Second, to get past this initial limitation, I attempted to input Qgis' output shapefiles to the website Aspose's page for converting shapefiles into svg files only to have it declare allQgis' shapefiles to be “invalid data.” I have a trouble report in with them about that.

I would prefer to use shapefiles to transfer the data – that is intended to be an interim format – however CorelDraw doesn't accept shapefiles (.shp) , but it does svg

On Wed, Sep 13, 2023 at 12:18 PM chris hermansen <clhermansen at gmail.com<mailto:clhermansen at gmail.com>> wrote:
Michael and list.

On Wed, Sep 13, 2023 at 10:22 AM Michael Edward McNeil <memcneil02 at gmail.com<mailto:memcneil02 at gmail.com>> wrote:
Chris, I could experiment with QGIS's cartography capabilities more if I could save my project, exit, and then resume working on it later. My other problem with QGIS interferes with that potential procedure.

Perhaps there is a degree of misunderstanding here.

When you work with say Microsoft Word to eventually produce a document that you will export to PDF to send to others, you don't save your interim work in PDF; you save it in Word's internal format, .docx.

Similarly with QGIS, you save an ongoing piece of work as a project. Look at the Project menu item, where you will see the ability to Save or Save As.  When you're ready to export your work to PDF or some other output format, there is an "export work flow".

There is also an important QGIS component not immediately visible, which is the Print Layout, also available in the Project menu item.

You might wish to follow through the online documentation here https://docs.qgis.org/3.28/en/docs/training_manual/map_composer/map_composer.html to see how that component is used to make a map, with surround, annotation, etc ready for export to PDF as a finished product.

So the overall workflow is to assemble the various layers you wish to depict on the main QGIS screen, applying symbology to each layer; then open a print layout to wrap up what's on screen into a full map composition.

Yes, aligning a single layer in another app with its true position is a problem. If I continue trying to do it this way, I'd probably also output meridians and possibly other clues (e.g., the British coastline) to allow aligning it properly.

Don't forget that you can add useful raster layers, like Open Street Map, to your screen and map composition, to save yourself a lot of time with respect to tracking down vector or raster data sets, symbolizing them, and so forth.

--
Chris Hermansen · clhermansen "at" gmail "dot" com

C'est ma façon de parler.

--
Chris Hermansen · clhermansen "at" gmail "dot" com

C'est ma façon de parler.
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