Jiri Drbalek

Hi Martin, have you tried to set `largest-bbox-only` to false?

@zdila Have you tried to set nodata value explicitly to the datasource? ```xml 255 ```

Have you been looking on visual test results? Many tests are broken. > So if #3966 (comment) should also be implemented here I will need some guidance of where to...

> I looked at the visual tests and to me it seemed that a lot of them show differences because of resampling methods. There are many tests with minor visual...

> I think I fixed the incorrect dimensions that were returned in the last commit. Great, I will try to take a look soon. > I also noticed that I...

Visual tests look good now. I had to add forgotten `filter_factor` . Can you, please, add commit https://github.com/mapycz/mapnik/commit/b4a8ef0ddef27f93d8bf03daba4ee2dd0bd5f583 to this pull request? `filter_factor` is an option of RasterSymbolizer to allow...

@flippmoke See [`attribute_collector.hpp#L178-L197`](https://github.com/mapnik/mapnik/blob/2929c4ae6db6d6c47eff9789bc5043d57ff3dc70/include/mapnik/attribute_collector.hpp#L178-L197). Filter factor is being set to 2.0 for scaling != near. It really make some sense for output quality, compare results from [gdal-filter-factor-1-bilinear.xml](https://github.com/mapnik/test-data-visual/blob/master/styles/gdal-filter-factor-1-bilinear.xml) and [gdal-filter-factor-2-bilinear.xml](https://github.com/mapnik/test-data-visual/blob/master/styles/gdal-filter-factor-2-bilinear.xml) ...

It's indeed strange logic. It seems to me as `filter_factor` was a hack to force resampling in Mapnik. Perhaps we can replace `filter_factor` in `mapnik::query` by resampling filter and pass...

> We will need a lookup table between the mapnik resampling methods and https://www.gdal.org/gdal_8h.html#a640ada511cbddeefac67c548e009d5ac so we can pass it to RasterIO. For that we need the resampling method as a...

@cpaulik > Do you think we need the last point? [Mapnik will not do any further resampling](https://github.com/mapnik/mapnik/blob/2929c4ae6db6d6c47eff9789bc5043d57ff3dc70/include/mapnik/renderer_common/process_raster_symbolizer.hpp#L82) if returned raster is of correct size. So I think there is no...