Maybe this could help a little.
I had a problem a while ago when I wanted to filter just the mask and then
assemble it again. It took some reading to get it right.
So I took the image apart with gdal_translate -b mask. Then ran gdal_sieve.py
where I got a 8 bit mask.
The tricky part was then the assembly. This is how I did the reassemble with
two gdalbuildvrt:
### Convert the mask to a real 1 bit mask with the right mask flags
### and deflate compression
echo "gdal_translate - real mask"
gdal_translate
-of GTiff
-ot Byte
-co NBITS=1
-co COMPRESS=DEFLATE
-mo INTERNAL_MASK_FLAGS_1=2
${TIF_TMP_DIR}/${TIF_FILE_NAME}_mask_separate_clean.tif
${TIF_TMP_DIR}/${TIF_FILE_NAME}_mask.msk
### Combine the image with the mask
gdalbuildvrt -b 1 ${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp_1.vrt
${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp.tif
gdalbuildvrt -b 2 ${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp_2.vrt
${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp.tif
gdalbuildvrt -b 3 ${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp_3.vrt
${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp.tif
echo "gdalbuildvrt"
gdalbuildvrt
-separate ${TIF_TMP_DIR}/${TIF_FILE_NAME}_combined.vrt
${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp_1.vrt
${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp_2.vrt
${TIF_TMP_DIR}/${TIF_FILE_NAME}_warp_3.vrt
${TIF_TMP_DIR}/${TIF_FILE_NAME}_mask.msk
echo "final gdal_translate"
gdal_translate
-b 1 -b 2 -b 3 -mask 4
-co COMPRESS=NONE
-co TILED=YES
-co BLOCKXSIZE=512
-co BLOCKYSIZE=512
-co INTERLEAVE=BAND
--config GDAL_TIFF_INTERNAL_MASK YES
--config GDAL_CACHEMAX 512
${TIF_TMP_DIR}/${TIF_FILE_NAME}_combined.vrt
${DATA_OUTPUT_DIR}/${TIF_FILE_NAME}.tif
Hope this helps you to take the image apart and then put back together again.
/Lars S.
11 februari 2021 kl. 18:37, "Patrick Young" <[email protected]
(mailto:[email protected]?to=%22Patrick%20Young%22%20<[email protected]>)>
skrev:
Not sure what the expected behavior is with gdalwarp and the underlying mask
preservation. It is kind of a tricky problem to solve in general; should the
mask be resampled with the same kernel as used in the warp? Or should it always
be NN? If the functionality is missing, this is a good opportunity to get your
employer funding gdal development.
A quick hack would be like you mention; you can extract the datamask
(gdal_translate -b mask ... i think) and then warp that separately, and
recombine.
P
On Thu, Feb 11, 2021 at 7:57 AM Daniele Romagnoli
<[email protected]
(mailto:[email protected])> wrote: Hi Jukka,
sorry but I can't share the data. Is owned by a customer :(
Long story short:
I have several raster tiles (with size around 5000x5000) and a shapefile
containing edges defining valid area of each tile.
I have used gdalrasterize to extract the needed crop for each tile to setup a
binary mask.
Then, I have combined the binary mask with the original tile and rewritten as a
new TIFF file with internal masks.
Then, I'm composing all the TIFF files to a VRT.
When rewriting that VRT to a mosaic TIFF, everything looks good. I see the
binary mask is used to properly compose/overlap/mask the pieces of the mosaic
and the output contains the mask too. This is an example of gdalinfo on one of
the mosaicked tiff:
Driver: GTiff/GeoTIFF
Files: out.tif
Size is 45842, 42506
Coordinate System is:
[... OMITTED... ]
Metadata:
AREA_OR_POINT=Area
Image Structure Metadata:
COMPRESSION=YCbCr JPEG
INTERLEAVE=PIXEL
JPEGTABLESMODE=1
JPEG_QUALITY=75
SOURCE_COLOR_SPACE=YCbCr
Corner Coordinates:
[... OMITTED... ]
Band 1 Block=256x256 Type=Byte, ColorInterp=Red
Mask Flags: PER_DATASET
Band 2 Block=256x256 Type=Byte, ColorInterp=Green
Mask Flags: PER_DATASET
Band 3 Block=256x256 Type=Byte, ColorInterp=Blue
Mask Flags: PER_DATASET
So, as you can see the masks are added to the mosaicked dataset.
However, when running
gdalwarp -t_srs EPSG:NEWCODE out.tif warped.tif
the binary mask is lost from the output file.
I have also tried using -dstalpha but it complains that "Destination dataset
has 3 bands, but at least 4 are needed" which makes sense.
So I was just wondering if there is anything I should be aware of when warping
a masked TIFF.
I would probably try to transform the binary mask to an alpha band, do the warp
and then convert back the alpha to a binary mask....
Thanks for any feedback in advance.
Regards,
Daniele
On Thu, Feb 11, 2021 at 3:27 PM jratike80 <[email protected]
(mailto:[email protected])> wrote: Hi Daniele,
Test data, please.
-Jukka Rahkonen-
Daniele Romagnoli-3 wrote
> Thanks for the feedback, Patrick.
> I have downloaded the latest build from GisInternals and it worked as
> expected.
> I have another question.
> It looks like warping an input file containing a binary mask isn't
> preserving the binary mask on the output.
> Should I specify any flag for that?
>
> Thanks for the help.
> Regards,
> Daniele
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