[QGIS-Developer] Raster pipeline issues

[Mathieu Pellerin]

+1

If in doing so we could unlock resampling for reprojected rasters, woupidou.


On Thu, Apr 16, 2020, 04:46 Martin Dobias <wonder.sk at gmail.com> wrote:

> Hi all
>
> With the recent addition of contour renderer of rasters I have
> realized there are artifacts coming to the renderer from the earlier
> stages (the raster data provider mainly). Another issue is that raster
> resampling (nearest neighbor / bilinear / bicubic) is only applied at
> the end of raster processing pipeline (i.e. after the contour renderer
> has been run), which does not really help for contours to get smooth
> contour lines (rather one gets some pixelated blurry output).
> Moreover, hopefully I am not the only one seeing occasional subtle
> "jumps" of raster data when zooming/panning map, which I would account
> to some small math errors in the QGIS raster code.
>
> Looking at the GDAL raster data provider in QGIS, there's quite some
> code complexity, with copying of data between temporary buffers and
> dealing with limitations that existed in GDAL < 2.0 (e.g. non-integer
> source windows).
>
> I am wondering what people think about simplifying the QGIS raster
> pipeline:
> - get rid of the last stage of the pipeline - resampling - and make it
> responsibility of data providers (i.e. GDAL) to return resampled data
> - get rid of the reprojector stage of the pipeline - and again make it
> responsibility of data providers (i.e. GDAL) to return already warped
> data
> - any other raster data provider not being able to do it internally
> would just use GDAL routines
>
> My hope is that we could get rid of a lot of raster related code and
> at the same time use GDAL's optimized code even more. I am not saying
> I will be working on this anytime soon, but I would be interested to
> hear what others think about the current state of the raster pipeline
> :-)
>
> Cheers
> Martin
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