On Fri, 2011-07-08 at 08:14 -0700, Michael Corey wrote:
> OK, I did a little more work on this, and I've narrowed down what's > going on, but I could still use some help in figuring out how to solve it. > > Here's my original image: > > http://mikejcorey.com/spatial/diablo-orig-5pct.tif > > The original appears to have an RGBA setup (RGB channels and an alpha > channel). > When I run this: > > gdalwarp -crop_to_cutline -cutline cutout.shp sourceimage.tif > diablo-cutline.tif > > Here's what I get: > > http://mikejcorey.com/spatial/diablo-cutline-5pct.tif > > This comes out as an RGB image with no alpha channel, with each channel > being semi-transparent. > Not in my case. Could there be something wrong with your GDAL setup? I drew a shapefile mask and ran the above command but my result is RGBA, the alpha band is not lost. See mask and result here: http://ubuntuone.com/p/13WR/ the output of gdalinfo: marius@mobi:~/Downloads$ gdalinfo diablo_cutl.tif Driver: GTiff/GeoTIFF Files: diablo_cutl.tif Size is 266, 224 Coordinate System is: PROJCS["NAD83 / UTM zone 10N", GEOGCS["NAD83", DATUM["North_American_Datum_1983", SPHEROID["GRS 1980",6378137,298.2572221010002, AUTHORITY["EPSG","7019"]], AUTHORITY["EPSG","6269"]], PRIMEM["Greenwich",0], UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4269"]], PROJECTION["Transverse_Mercator"], PARAMETER["latitude_of_origin",0], PARAMETER["central_meridian",-123], PARAMETER["scale_factor",0.9996], PARAMETER["false_easting",500000], PARAMETER["false_northing",0], UNIT["metre",1, AUTHORITY["EPSG","9001"]], AUTHORITY["EPSG","26910"]] Origin = (693798.721929854014888,3902305.751849883235991) Pixel Size = (20.022668877344305,-20.040546259961307) Metadata: AREA_OR_POINT=Area Image Structure Metadata: INTERLEAVE=PIXEL Corner Coordinates: Upper Left ( 693798.722, 3902305.752) (120d52'12.04"W, 35d14'42.43"N) Lower Left ( 693798.722, 3897816.669) (120d52'15.84"W, 35d12'16.81"N) Upper Right ( 699124.752, 3902305.752) (120d48'41.44"W, 35d14'38.67"N) Lower Right ( 699124.752, 3897816.669) (120d48'45.35"W, 35d12'13.05"N) Center ( 696461.737, 3900061.211) (120d50'28.67"W, 35d13'27.75"N) Band 1 Block=266x7 Type=Byte, ColorInterp=Red Mask Flags: PER_DATASET ALPHA Band 2 Block=266x7 Type=Byte, ColorInterp=Green Mask Flags: PER_DATASET ALPHA Band 3 Block=266x7 Type=Byte, ColorInterp=Blue Mask Flags: PER_DATASET ALPHA Band 4 Block=266x7 Type=Byte, ColorInterp=Alpha -marius > However, if I do this: > > gdalwarp -dstalpha -crop_to_cutline -cutline cutout.shp sourceimage.tif > diablo-dstalpha-cutline.tif > > I get this: > > http://mikejcorey.com/spatial/diablo-dstalpha-cutline-5pct.tif > > This one is strange, because it appears to be a grayscale image. But > when I open it in Photoshop, I see that it actually has 4 alpha > channels. I suspect that those are just getting set incorrectly as alpha > and are in fact the RGB channels, but can someone explain that behavior > or how to fix it? > > What I want to end up with is a clipped RGB image (or RGBA) image where > nodata is transparent and the RGB isn't translucent. > > Thanks again! > > Michael Corey > > > > 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 >
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