[gdal-dev] Question about gdaladdo and raster mosaicking

[Ammar]

Chaitanya,

Thank you very much for your
 reply and suggestion. I have used LZW with predictor 2 compression and 
added external overviews compressed in LZW too and the image came 
perfect. The only downside is the size of each of the images has 
expanded from approx. 2 GB to 18-20 GB. So now I have to choose between 
quality and size!

Attached are two screen shots showing the difference.

Thanks again!

Regards,
Ammar



________________________________
 From: Chaitanya kumar CH <chaitanya.ch at gmail.com>
To: ammar83_h at yahoo.com 
Cc: gdal dev <gdal-dev at lists.osgeo.org> 
Sent: Tuesday, January 21, 2014 6:27 PM
Subject: Re: Question about gdaladdo and raster mosaicking
 


Ammar,
You are using lossy JPEG compression. I'm guessing that the white lines are are actually pixels with values near but not equal to 255. So, they are not treated as nodata pixels.
My suggestion is to use another format with lossless compression for the 21 images or use a mask band if you prefer.
Let me know how it goes.
--
Best regards,
Chaitanya Kumar CH
On 21-Jan-2014 5:31 pm,  <ammar83_h at yahoo.com> wrote:

Hello Chaitanya,
>
>I was looking online for solutions to my problem and I cam across some of your posts so I thought you might help me with my problem.
>
>I have 10,000+ TIFF files that I want to merge into one big Image and serve using GeoServer. I merged every 500 images at a time creating using gdalbuildvrt and gdal_translate along with JPEG compression creating 21 TIFF files. I added overviews then to each of the new 21 files. When adding the images together, once directly as files using QGIS and another time as WMSs using GeoServer, I got white lines/gaps precisely at the border of ever 2 images. I thought the problem is with no data values but I decided to take another approach and merged all the 10,000 files into one huge image and this time I got one perfect image with no lines or gaps. I failed to create overviews for the big image because the process took days or gdaladdo running with no progress. I tested then on smaller images with and without overviews and the ones with no overview came perfect while the one with gdaladdo overviews came with the same problem of lines and gaps. The commands I
 m using are the following:
>
> gdalbuildvrt -srcnodata 255 -vrtnodata 255 -a_srs EPSG:27700 -input_file_list tiff_list.txt mosaic.vrt
>
>gdal_translate -of GTiff -co TILED=YES -co BIGTIFF=YES -co COMPRESS=JPEG -co JPEG_QUALITY=80 -co BLOCKXSIZE=512 -co BLOCKYSIZE=512 -co PHOTOMETRIC=YCBCR mosaic.vrt mosaic.tif
>
>gdaladdo mosaic.tif -r average --config COMPRESS_OVERVIEW JPEG --config JPEG_QUALITY_OVERVIEW 60 --config INTERLEAVE_OVERVIEW PIXEL --config PHOTOMETRIC_OVERVIEW YCBCR 2 4 8 16 32 64 128 256 512
>
>Any ideas, tips or recommendations would be appreciated!
>
>Best regards,
>Ammar
>
>_____________________________________
>Sent from http://osgeo-org.1560.x6.nabble.com
>
>
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