Mosaic to New Raster adds white background

[JakubWabinski]

Hey guys,

I am preparing a bigger script for spatial data processing using, inter alia, arcpy.

 Part of the script is supposed to mosaic the newly added raster datasets to a geodatabase. The original rasters have no background but after using the Mosaic to New Raster function, a white background is added. I know that this background can be masked out in the symbology pane but I would like to handle it using arcpy. Could you please suggest a solution?

Before mosaicing

After mosaicing

[MichaelS]

Hi Jakob, It looks like the tool is assigning a background value  to your mosaic. You could try checking the value of the white background, then setting your no data value to that value in the Environments pane of the Mosaic to New Raster tool, re-run and see if that helps. 

[JakubWabinski]

Thanks for your answer. But the mosaic has 4  8-bit bands. What should I write there? 255 only or rather 255,255,255?

[MichaelS]

Just 255 should be sufficient.

[JakubWabinski]

Still having the same issue. I tried with both: writing 255 and setting the parameter to 'maximum'. Any other ideas?