Michael, another option is to use gdalwarp to merge images together.
Brian On Thu, 2011-07-07 at 09:47 -0700, Michael Corey wrote: > Thanks for your responses, Chaitanya and Eli. The semitransparency isn't > really noticeable until you put the image on top of something else (in > Photoshop or another program). > > It looks like the problem is actually in my gdal_merge.py command. > That's where the semitransparency is getting introduced. > > gdal_merge.py -init "255" -o diablo-combined-utm10.tif file file file > > What I'm trying to get is a merged image where no data = transparent. > Would this be correct in that case? > > gdal_merge.py -n "255" -ul_lr 380309.272908 4653610.244134 > 1317796.950998 3614484.073320 -o test-combined.tif file file file > > Michael Corey > Digital Innovations Editor > Center for Investigative Reporting > 510.809.3178 > > > On 7/7/11 7:13 AM, Eli Adam wrote: > > Michael, > > > >>>> On 7/6/2011 at 5:35 PM, in message<4e14ff42.50...@cironline.org>, Michael > > Corey<mco...@cironline.org> wrote: > >> Sure, I've uploaded samples here. > >> > >> http://www.mikejcorey.com/spatial/diablo-box-sample.tif > >> http://www.mikejcorey.com/spatial/diablo-cutout-sample.tif > > I don't notice the semi-transparency in these scaled down images. Perhaps > > it is the way your viewer reads the mask? > > > >> These are the same as the images created by the process I described (but > >> scaled down). > >> > >> To your point about specifying size in the first step -- will that make > >> the process run faster, or does it do the scaling down after it builds > >> the full-resolution image? > >> > >> Also, I notice that my filesize always gets significantly bigger when I > >> do the cutout step, which seems counter-intuitive to me since in theory > >> shouldn't there be less information present once the cutout is done? > > -cutline does not 'discard' any data. The extent of the data remains the > > same unless you reset those extents. You can do that with > > -crop_to_cutline. Here are some details from the gdalwarp page, > > http://gdal.org/gdalwarp.html : > > > > -crop_to_cutline: > > (GDAL>= 1.8.0) Crop the extent of the target dataset to the extent of > > the cutline. > > > > Polygon cutlines may be used as a mask to restrict the area of the > > destination file that may be updated, including blending. If the OGR layer > > containing the cutline features has no explicit SRS, the cutline features > > must be in the georeferenced units of the destination file. When outputing > > to a not yet existing target dataset, its extent will be the one of the > > original raster unless -te or -crop_to_cutline are specified. > > > > Best Regards, Eli > > > >> Thanks for your help! > >> > >> Michael Corey > >> > >> > >> On 7/6/11 5:01 PM, Chaitanya kumar CH wrote: > >>> Michael, > >>> > >>> Can you provide screenshots of > >>> diablo-combined-center-utm10-70pct-box.tif and > >>> diablo-combined-center-utm10-70pct-cutout.tif for comparison? > >>> > >>> By the way, you can perform the actions of the two gdal_translate > >>> commands in the first step with the gdal_merge.py script itself unless > >>> you want to use a specific resampling algorithm. > >>> > >>> On Thu, Jul 7, 2011 at 4:28 AM, Michael Corey<mco...@cironline.org > >>> <mailto:mco...@cironline.org>> wrote: > >>> > >>> Hi all: > >>> > >>> I'm using a shapefile as a clipping mask to cut out the shoreline > >>> from some DOQ files that I have merged together. But when I do the > >>> clipping step, I end up with unwanted semitransparency in the > >>> non-clipped areas. > >>> > >>> I'm pretty sure the problem is only with my gdalwarp step at the end. > >>> > >>> Here's my process: > >>> > >>> gdal_merge.py -init "255" -o diablo-combined-center-utm10.tif file > >>> file file file > >>> > >>> gdal_translate -outsize 70% 70% diablo-combined-center-utm10.tif > >>> diablo-combined-center-utm10-70pct.tif > >>> > >>> ogrinfo -al ./diablo_canyon_detail_clipper.shp > >>> //Extent: (XXXX, YYYY) - (XXXX, YYYY) > >>> > >>> gdal_translate -projwin XXXX YYYY XXXX YYYY > >>> diablo-combined-center-utm10-70pct.tif > >>> diablo-combined-center-utm10-70pct-box.tif > >>> > >>> gdalwarp -co COMPRESS=DEFLATE -cutline > >>> ./diablo_canyon_detail_clipper.shp > >>> diablo-combined-center-utm10-70pct-box.tif > >>> diablo-combined-center-utm10-70pct-cutout.tif > >>> > >>> Can anyone help? > >>> > >>> Thanks! > >>> > >>> -- > >>> Michael Corey > >>> > >>> _______________________________________________ > >>> gdal-dev mailing list > >>> gdal-dev@lists.osgeo.org<mailto:gdal-dev@lists.osgeo.org> > >>> http://lists.osgeo.org/mailman/listinfo/gdal-dev > >>> > >>> > >>> > >>> > >>> -- > >>> Best regards, > >>> Chaitanya kumar CH. > >>> /t?a???nj?/ /k?m?r/ > >>> +91-9494447584 > >>> 17.2416N 80.1426E > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
