https://github.com/timwaters/gdal_gdaladdo_issue
Bunch of files etc to help debug a gdaladdo error with transparency and nodata. now fixed.
https://github.com/timwaters/gdal_gdaladdo_issue
Last synced: 5 months ago
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Bunch of files etc to help debug a gdaladdo error with transparency and nodata. now fixed.
- Host: GitHub
- URL: https://github.com/timwaters/gdal_gdaladdo_issue
- Owner: timwaters
- Created: 2017-10-05T16:26:22.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2017-10-06T12:13:57.000Z (over 8 years ago)
- Last Synced: 2025-08-09T02:32:47.080Z (11 months ago)
- Homepage:
- Size: 1.62 MB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
Awesome Lists containing this project
README
A repo to help work out what was going on with a sequence of commands to add overviews to rasters.
The **fix** was to add add `-dstnodata none` to the gdalwarp call. Thanks to Even Rouault, lead of the GDAL project for helping me with this.
```
#set up
cp treasure_island.orig.tif treasure_island.tif
rm treasure_island_warped.tif
#Apply overviews to ungeoreferenced raster
gdaladdo -r average treasure_island.tif 2 4 8 16
#Rasterise ungeoreferenced raster with the cropping mask
gdal_rasterize -i -b 1 -b 2 -b 3 -burn 17 -burn 17 -burn 17 20.gml -l features treasure_island.tif
#Georeference the raster
gdal_translate -a_srs '+init=epsg:4326' -of VRT treasure_island.tif temp.vrt -gcp 100.38, 83.096, -122.377, 37.830 -gcp 430.1966, 370.08, -122.363, 37.8207 -gcp 313.69, 61.68, -122.368, 37.831
gdalwarp -rn -dstalpha -srcnodata '17 17 17' -s_srs 'EPSG:4326' temp.vrt treasure_island_warped.tif -co TILED=YES -co COMPRESS=LZW
#Apply overviews to georeferenced raster
gdaladdo -r average treasure_island_warped.tif 2 4 8 16
#Expected - transparent areas in overviews should be 17,17,17 with alpha of 0
#Observed - transparent areas in overviews are 17,17,17 with alpha also set to 17
gdaladdo -r nearest treasure_island_warped.tif 2 4 8 16
#Expected - transparent areas in overviews should be 17,17,17 with alpha of 0
#Observed - transparent areas in overviews are 17,17,17 with alpha of 0
```
Screenshots from Gimp
With average:
With nearest:
Showing what it looks like in mapwarper
# FIX
add -dstnodata none to the gdalwarp call.
```
gdalwarp -rn -dstalpha -srcnodata '17 17 17' -dstnodata none -s_srs 'EPSG:4326' temp.vrt treasure_island_warped.tif -co TILED=YES -co COMPRESS=LZW
```