On lundi 25 juin 2018 13:10:16 CEST Kalev Julge wrote: > 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.
After your gdalwarp to VRT, do: gdal_translate new.vrt new.jpg -of JPEG You cannot directly wrap to JPEG, because of the driver limitation See https://trac.osgeo.org/gdal/wiki/FAQRaster#Whywontgdalwarporgdal_mergewritetomostformats > It seems that GDAL doesn’t create new JPEG files without having pre-existing > JPEG-s to modify. Actually, that's right the opposite :-) > If I try to modify old JPEG, I get a message “Output > dataset exists, but cannot be opened in update mode. That means you cannot modify an existing JPEG. You have to recreate a completely new file. > 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)” The second argument must be a GDALDataset* object, not a string, so do something like GDALDataset* srcDS = reinterpret_cast<GDALDataset*>( GDALOpen("old.jpg", GA_ReadOnly)); GDALDataset* outDS = jpegDriver->CreateCopy( "new.jpg", srcDS, FALSE, NULL, NULL, NULL); GDALClose(outDS); GDALClose(srcDS); Even -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] https://lists.osgeo.org/mailman/listinfo/gdal-dev
