[gdal-dev] using gdal.Warp to reproject a GTiff with an external nodata mask (.msk)

[Even Rouault]

Maxime,


you need to do in 2 steps, with something like (didn't test, slight 
modifications may be needed):

- slightly modify your first step, to reproject to an intermediate RGBA 
dataset, with dstAlpha=yes. That temporary dataset may be a VRT, or a 
GeoTIFF with a lossless compression (ie DEFLATE)

- convert from RGBA to RGB+mask with gdal.Translate(out, 
tmp_dataset_of_previous_step, bandList=[1,2,3], maskBand=4, 
creationOptions=["COMPRESS=JPEG", "PHOTOMETRIC=YCBCR", "TILED=YES", 
"BIGTIFF=YES"])


Even


Le 27/01/2025 à 16:58, Maxime Demers via gdal-dev a écrit :
> Hi everybody, I hope you are all well!
>
> I have an issue that I would need help about if possible.
> I would like to use the GDAL Python bindings to reproject a TIFF that 
> has an external nodata mask stored in a separate |.msk| file. Also, 
> this is important to me to keep the jpeg compression.
> After some tests, I found out that |gdal.Warp| does not reproject the 
> |.msk|
> Is there  a way to acheive what I am trying to do?
> |import os from osgeo import gdal IN_RASTER = os.path.join(r"C:\\", 
> "data", "Ortho", "Ortho2024_32187_10cm_mask.tif") OUT_RASTER = 
> os.path.join(r"C:\\", "data", "Ortho", "Ortho2024_3857_10cm_mask.tif") 
> src = gdal.Open(IN_RASTER) dst = gdal.Warp(    OUT_RASTER,    src,   
>  format="GTiff",    dstSRS="EPSG:3857",   
>  creationOptions=["COMPRESS=JPEG", "PHOTOMETRIC=YCBCR", "TILED=YES", 
> "BIGTIFF=YES"],    callback=gdal.TermProgress_nocb ) dst = None|
>
>
>
> 	
>
> **
>
> *Maxime Demers*
>
> Analyste en géomatique
>
> Service de la planification
>
> et de la gestion du territoire
>
> Tél. : 819 823-8000 poste 2360
>
>
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