qgisraster
When I export my map from Print Composer in QGIS 1.7.4, an odd red band appears across the middle of the image. This happens when I export to both PNG and PDF. Its not visible on the screen before export, or present in the original raster image.
The band is to the left of the island halfway down the coast, below Pwani.
Any ideas what's causing this and how to fix it?
The fix would be to not include a period . in the output file name. I have verified this in QGIS version 3.6.2-Noosa
Example, if your print composer layout is named Atlas test-8.5x11, when you output a raster, then be sure to name the output file without any extra ., e.g., Atlas test-85x11.tif.
For vector output, such as PDF or SVG, you do not have to do anything different, as it will work as expected.
This QGIS issue, https://github.com/qgis/QGIS/issues/26308, titled Error exporting layout with "." (full stop) in filename mentions the error code
"Cannot write to
<FILE_LOCATION>. This file may be open in another application." The file is not open in another application.
Best Answer
This seems to happen when you use a semi-transparent raster layer. Look at this
QGIS composer - How can I eliminate striping across transparent raster layers?
which describes exactly the same problem. It seems to be a bug, and as far as I know It has not been solved in 1.8 (tried in ubuntu and win7). So, the solution, is avoiding the use of semi-transparent raster in your composition. If you have a shaded relief model with no transparency, everything should be fine, no striping.