[gdal-dev] warp/trsnalte a specific src_ovr without alpha band

[Even Rouault]

On dimanche 7 juillet 2019 12:13:04 CEST Idan Miara wrote:
> Hi,
> 
> I have a RGBA raster with overviews, I'd like to cut an extent from a
> specific overview into a new YCbCr JPEG raster.
> I want to drop the alpha band (I don't need it and it is not supported in
> YCbCr).
> 
> I couldn't find a way to do it because:
> 1. with gdal_translate I could choose bands (RGB) but I couldn't given a
> src_ovr,

You can do it in 2 steps. Note the size of the overview you are interested in. 
Imagine that in.tif has dimensions 21x13 and an overview of 11x7

Do:
gdal_translate in.tif ovr.vrt -outsize 11 7 -of VRT -b 1 -b 2 -b 3
gdal_translate ovr.vrt extract.tif [-srcwin | -projwin] -co COMPRESS=JPEG -co 
PHOTOMETRIC=YCBCR

~~~

Or you can do it in one step by using the generic OVERVIEW_LEVEL open option.
See the papszOpenOptions of
https://gdal.org/api/raster_c_api.html#_CPPv410GDALOpenExPKcjPPCKcPPCKcPPCKc

If the overview level you're interested in is the first one (index 0), then

gdal_translate in.tif extract.tif  -b 1 -b 2 -b 3 [-srcwin | -projwin] -co 
COMPRESS=JPEG -co PHOTOMETRIC=YCBCR -oo OVERVIEW_LEVEL=0

Even

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