[postgis-users] QGIS Loads Black Screen For PostGIS Out-DbRaster Data

[Osahon Oduware]

Hi Regina,

Yes, the information you provided is very helpful. Thanks a lot.

On Sun, Apr 23, 2017 at 9:56 PM, Regina Obe <lr at pcorp.us> wrote:

> Couple of updates here:
>
>
>
> The srid issue with the raster2pgsql transforming instead of setting srid,
> I confirmed to be an unintentional feature (bug however you want to think
> of it).
>
>
>
> I've patched it up here:
>
> https://trac.osgeo.org/postgis/ticket/3738
>
>
>
> I think this issue wasn't discovered because using the –Y (which means
> copy mode) is much more efficient than without –Y (which uses INSERT
> statements) and when you use the –Y, the system doesn't try to transform,
> and does do the correct set srid because the transform logic relies on
> ST_Transform which can't be done in copy mode.
>
>
>
> So the work around for the broken versions is to use the –Y switch.  You
> should probably just always use the –Y switch when you don't need to
> transform, which you can't do very well with the broken version.
>
>
>
> raster2pgsql -C -t 500x500 -R -Y -s 26918 -F -I C:/gisdata/*.jp2 nj_aerials
>
>
>
> When I do that transform is not attempted and the rasters stay out of
> database, but the SRID is set to what I specified.
>
>
>
> On a related note, I tested QGIS and ran into the same issue as Osahon
> that the out-db does not show.
>
>
>
> However if I build overviews and select the out-db it shows until I zoom
> into the image.
>
>
>
> I think this happens because zooming in forces it to use the out-db table
> instead of the overviews. I guess the driver is trying to use the raw bytes
> instead of using the built in raster functions for display.
>
> Not sure how hard of a fix that would be to fix the GDAL postgis raster
> driver as I suspect it's the GDAL driver at fault and not QGIS.
>
>
>
> Hope this helps,
>
> Regina
>
>
>
> *From:* postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] *On
> Behalf Of *Osahon Oduware
> *Sent:* Wednesday, April 19, 2017 11:52 AM
> *To:* PostGIS Users Discussion <postgis-users at lists.osgeo.org>
> *Subject:* Re: [postgis-users] QGIS Loads Black Screen For PostGIS
> Out-DbRaster Data
>
>
>
> Hi Tumasgiu,
>
> Sorry, for not updating you. Yes, I followed up on your suggestion and
> Regina, Adrian, and some others assisted me in building PostGIS with a
> MrSID-enabled GDAL. My Out-DB rasters are in the MrSID format.
>
> This raster file exist on the filesystem and when it is loaded directly
> into QGIS it displays the image (aerial photo). Also, when the same file is
> stored in PostGIS as a raster (IN-DB), it can be viewed in QGIS (using the
> DB Manager tool). However, when I reference the same file as an OUT-DB
> raster in PostGIS (in this case only the metadata of the raster and the
> filepath to the raster file is stored), an attempt to view it in QGIS
> (using the DB Manager tool) results in a black image being displayed
> instead of the aerial photo.
>
>
>
>
>
> On Wed, Apr 19, 2017 at 4:41 PM, Tumasgiu Rossini <rossini.t at gmail.com>
> wrote:
>
> Hi,
>
> What is the format of your rasters ?
>
> With your precedents messages in mind, I guess that the format is Mr.SID,
>
> can you confirm that ?
>
> (if so, then it means that you have managed your first postgis build, so
> congrats !)
>
> It's important to give as much as detail as possible if you want help.
>
>
>
>
> 2017-04-18 15:43 GMT+02:00 Osahon Oduware <osahon.gis at gmail.com>:
>
> Hi All,
>
>
>
> I have an out-db raster on PostGIS which I tried to load in QGIS (v
> 2.14.12-Essen) utilizing the DB Manager to establish a connection. I could
> view the raster table, but when I try to "Add to canvas" it displays a
> black screen instead of the raster image.
>
>
>
> I would be glad if someone could help me to resolve this.
>
>
>
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