Unable to export large / high resolution / detailed scale maps

[bderstine]

From Print Composer:

1. Change Quality 300 dpi to 500 or 600 for example.
2. Export to Image... (png) OR Export to PDF...
3. OK...

Error: Exception. Bad Allocation. (see attached image)

The current print composer layout is lost and apparently irretrievable unless it was saved with the .qgs file.

[bderstine]

Error Message Screen Capture

[gislab]

I cannot confirm, just tried on WinXP, r15700.

Can you provide more specifics on what are you doing, what data are you using (if any) and QGIS revision.

[mayeulk]

I successfully created an A4 600 dpi map (11Mb in png, 3 Mb in vector pdf) on Kubuntu 10.10 (64 bits).

However, I tried an A0 at 600 dpi in png, it failed. First I was asked:

To create image 28086x19866 requires about 1673 MB of memory. Proceed?

I clicked yes (my PC has 4GB of RAM). Then there was the message:

Creation of image with 28086x19866 pixels failed. Export aborted.

No crash for me however. My test dataset is pure vector: OSM data for Milano and surrounding, stored on postgis thanks to osm2postgresql, using rule-based render.

I was able to export the above in A0 but in vector pdf (20 Mega bytes). If you can export in vector pdf, you can convert later on in raster, as a workaround (for instance, gimp does this, but command line solutions might be less memory hungry).

[mayeulk]

I made a tougher test: export 20% of OSM data for Italy on a 11 meter by 8 meter (sic) pdf vector map. It crashed after a few minutes (Kubuntu 10.10 64 bits, qgis trunk 1.7.0 r15718).

It seems that the size limit for getting the bug is OS or machine specific. @gislab: what if you try to export a very large file?

[gislab]

Replying to mayeulk:

To create image 28086x19866 requires about 1673 MB of memory. Proceed? I clicked yes (my PC has 4GB of RAM). Then there was the message: Creation of image with 28086x19866 pixels failed. Export aborted.

It failed with the same message on WinXP, r15740. It might be running into some system limitations, the file that is being created would have 600 millions pixels.

[aghisla]

I'm running QGIS r15724, Fedora 14, 2GB RAM, and I get the same messages as mayeulk and gislab, if I try to export in A0 at 600 dpi in png format.

If I choose a higher resolution (800 dpi), then I directly get the Export aborted message, without any crash.

[bderstine]

Was away for a bit, here are the answers to all of the great questions and discussion that have been going on... At the time of reporting, I was running 15622. I have since updated to 15740 and it appears to be resolved as far as I can tell.

My data is all basic shapefiles, census county boundaries, plus a few million point features, and the standard map elements: scale bar, title, north arrow, legend, notes.

Another symptom of the crash was that my composer window would go blank (As you can see in the attached photo). I would have to shut down qgis, don't save the file, and reopen in order to get my saved composer layout back.

[lutra]

I tested on Ubuntu machine 32 bit 4gb of ram, qgis trunk.

I added a 3gb raster image and created a A0 layout, streching the image almost at full layout extent.

I can produce a PDF at 300dpi and 400 dpi. At 500dpi QGIS crashes silently with a seg fault.