[mapserver-users] MapServer returns a blank image when requesting a square image

[Rahkonen Jukka (MML)]

Hi,

I have been using a spatialite layer as a tileindex for years without problems so definitely that is not a bug that affects all users and use cases. Try to create a zip file that contains everything that is needed for reproducing the issue. Let’s hope that you can make it with a spatialite database and two images in the tileindex.

Have you already tried to add explicit PROJECTION blocks into both LAYERs?

-Jukka Rahkonen-



Lähettäjä: mapserver-users [mailto:mapserver-users-bounces at lists.osgeo.org] Puolesta Pablo Sanfilippo
Lähetetty: 11. tammikuuta 2018 14:46
Vastaanottaja: Seth G <sethg at geographika.co.uk>
Kopio: mapserver-users at lists.osgeo.org
Aihe: Re: [mapserver-users] MapServer returns a blank image when requesting a square image

Oh, so this is a definitely a bug. Is it reported yet in the issue tracker?

On Wed, Jan 10, 2018 at 3:55 PM, Seth G <sethg at geographika.co.uk<mailto:sethg at geographika.co.uk>> wrote:
Hi Pablo,

Just to note I also ran into this issue so you are not alone!
A WMS request from OpenLayers to MapServer would be fine, but modifying the size of the image (WIDTH and HEIGHT parameters) would result in a blank image and no errors in the logs.
I never got a chance to debug further though. An error should ideally be reported somewhere rather than a blank, seemingly valid, image.

Seth

--
web:http://geographika.co.uk
twitter: @geographika


On Wed, Jan 10, 2018, at 6:46 PM, Pablo Sanfilippo wrote:
Hi all,

I admit this is the weirdest issue I have come across. This are the relevant parts of my MapServer configuration:

# A valid mapfile used for testing
MAP
  NAME valid
  STATUS ON
  PROJECTION
    "init=epsg:4326"
  END

  IMAGECOLOR 0 0 0
  TRANSPARENT ON

  WEB
    METADATA
      "wms_srs"             "EPSG:4326 EPSG:3857"
  END
  END

  LAYER
    NAME "index"
    STATUS ON
    TYPE POLYGON
    CONNECTIONTYPE POSTGIS
    CONNECTION "host=x port=x dbname=x user=x password=x"
    DATA "geometry from (select i.geometry, i.id<http://i.id>, '/vsis3/' || i.s3_bucket || '/' || i.s3_key as location from images_image) as index using unique id"
    CLASS
      STYLE
        OUTLINECOLOR 0 0 0
        WIDTH 1.0
        COLOR 200 200 200
        ANTIALIAS true
      END
    END
  END

  LAYER
    NAME "images"
    STATUS ON
    TILEINDEX "index"
    TILEITEM "location"
    TYPE RASTER
    PROJECTION
      AUTO
    END
    METADATA
      "wms_title"           "Images"
    END
  END


END

The data in the PostGIS index is in EPSG:4326. The images referenced by the index are GeoTIFFs georeferenced in EPSG:4326.

A WMS request for the index layer shows the index polygons fine, whatever the SRS and image size in the request.
A WMS request for the images layer using SRS=EPSG:4326 shows the images fine, whatever the image size.
A WMS request for the images layer using SRS=EPSG:3857 will work fine as long as the requested image size's x is greater than or equal to the y. If not, it will return a blank (transparent) image. For example, a 1300x1299 image will work fine, a 1300x1300 image won't work and 1301x1300 won't work either.

Any clues?

Thanks!
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