# Geoserver “Layer Groups” with Raster Layer

I need to group multiple geotiff raster layers together. Each layer works well on its own when being previewed through the "Layer preview" utility.

However, when I group the layers together through the "Layer Groups" utility, the created grouped layer is previewed as an empty/white layer.

I am a bit suspicious that the problem lies in the coverage band details (palette_index). I am a web developer who is trying to integrate the layers in a website and therefore I don't have an experience in what does the coverage band details exactly mean.

I am attaching the configuration screen of two of the tiff files I am referring to.

Update 1: I have now pasted the geoserver log, does this show a memory related issue? One line says: 2015-10-25 06:02:42,864 ERROR [geotools.map] - Call MapContent dispose() to prevent memory leaks. You can view the log of 1000 lines here: http://jpst.it/CFPL

• Could you check your geoserver.log for a relevant log message? You may be hitting a memory limit for example. – bosth Oct 24 '15 at 17:03
• I have now added a log file, could you please check if this means a memory issue? – perpetual_dream Oct 25 '15 at 6:09

I have the exact same problem for single tif files. If there are multiple tif files in the directory using the ImageMosaic plugin works without problems. To get rid of the error

ERROR [geotools.rendering] - Argument "bgColor" should not be null.

I just had to adjust the InputTransparentColor (FFFFFF) for the layers that are part of the grouplayer:

The plugin is not able to handle single tif files! I did not find similar configuration possibilities for WoldImages. There are two workarounds I can think of to make use of the ImageMosaic plugin for a single tif:

• You could create a second tif (copy) with the exact same extents like the first and create a tfw file that makes the copy tif a neighbor of the original tif. Since the content is not relevant you could just use a complete white tif for that. (The layer boundingbox coordinates can be adjusted to just match the original tif afterwards)

• The second option would be to split the tif in multiple tif files.

There is an error saying Argument "bgColor" should not be null.

There is no background colour argument in your request as it is received by the server (you can see this in the logs). Are you using the built-in later preview for your request?

As a temporary work around, can you try adding an explicit background colour in your request, even though this shouldn't be necessary: bgcolor=0xffffff?

I would suggest to check a different approach. Try using the ImageMosaic plugin if the geotiff file are coherent (e.g. an aerial mosaic).

See this link for an intro.

I had this same problem on cascaded WMS layers. An upgrade to the latest GeoServer 2.8 was helpful for me, the problem with bgColor should not be null seeem to be resolved there.