I've been using QGIS 2.6 (Brighton) happily for awhile but suddenly it became extremely slow during certain operations, after being reasonably fast in past use. I'm merging NAIP JP2 files to virtual raster, reprojecting the raster to another vrt, then clipping that raster and using gdal_retile to cut it into tiles. All files are on an external USB hard drive.

It takes more than 24 hours for the Mac (2.9ghz Core i5, 8gb ram, Yosemite 10.10.1) to cut a single tile. Meanwhile, duplicating the exact same steps, a quad core i5 Windows machine outputs a tile every 29 minutes. I certainly didn't expect the Mac to be faster - the Windows machine is speedier, but it is slower by a factor of 10 or more.

What is very strange is that I used to be able to cut a single tile using a vector shape as a mask layer in about an hour. Now, that also takes over a day. I've tried deleting and re-installing QGIS and the KyngChaos frameworks but the problem persists.

Any suggestions about what may be causing this?

  • So it 'suddenly' became extremely slow? It was working quickly (i.e. similar to Win machine) before? – Simbamangu Feb 20 '15 at 15:46
  • Yes. I've edited the question to clarify that. – Krizbleen Feb 20 '15 at 18:08
  • Do you have the Intergraph ECW/JP2 driver installed correctly? If not you're probably falling back to the default OpenJP2 driver which is horrendously slow. – user2856 Feb 20 '15 at 19:34
  • 1
    Can you edit your question to provide a gdalinfo report for one of the images from both the Mac and Windows PCs. – user2856 Feb 21 '15 at 4:58

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