Hi Doug, Thanks for the info. I know that JPEG is lossy but our datasets are very large. That’s why we use JPEG, which is good enough for our needs and the file sizes are smaller.
It seems that GDAL doesn’t create new JPEG files without having pre-existing JPEG-s to modify. If I try to modify old JPEG, I get a message “Output dataset exists, but cannot be opened in update mode. I also tried using “CreateCopy” but that produced syntax error. Used command on GDAL CMD: “GDALDriver::CreateCopy ("new.jpg","old.jpg", FALSE, NULL, NULL, NULL)” Kalev From: Doug Newcomb <doug_newc...@fws.gov> Sent: Thursday, June 21, 2018 5:24 PM To: Kalev Julge <kalev.ju...@reach-u.com> Cc: gdal dev <gdal-dev@lists.osgeo.org> Subject: Re: [EXTERNAL] [gdal-dev] Convert VRT+JPEG with gdalwarp Kalev, Just set the output file format to -f JPEG format ( .jpg) or -f JP2OpenJPEG (.jp2) The JPEG format will be lossey by default. Is that what you want? See: https://medium.com/planet-stories/a-gentle-introduction-to-gdal-part-1-a3253eb96082 https://medium.com/planet-stories/a-gentle-introduction-to-gdal-part-2-map-projections-gdalwarp-e05173bd710a Doug On Thu, Jun 21, 2018 at 10:00 AM kalevj <kalev.ju...@reach-u.com<mailto:kalev.ju...@reach-u.com>> wrote: Hello, I used gdalwarp to transform a VRT+JPEG pair from one EPSG projection to another. Everything worked well. This conversion changed the VRT file so that reprojection takes place when the images are loaded. However, I would need to reproject the JPEG so that there would not be a need to reproject every time the images are loaded. Is it possible somehow? I used the command: "gdalwarp -s_srs EPSG:2006 -t_srs EPSG:3857 -of VRT -r near old.vrt new.vrt" Thanks! Kalev -- Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org<mailto:gdal-dev@lists.osgeo.org> https://lists.osgeo.org/mailman/listinfo/gdal-dev -- Doug Newcomb USFWS 551F Pylon Dr Raleigh, NC 919-856-4520 ext. 14 doug_newc...@fws.gov<mailto:doug_newc...@fws.gov> --------------------------------------------------------------------------------------------------------- NOTE: This email correspondence and any attachments to and from this sender is subject to the Freedom of Information Act (FOIA) and may be disclosed to third parties.
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