[FWTools] gdal_merge with a specific pixel value clipped/removed

[Ari Simmons]

Interesting...ok, so (knowing nothing about .vrt's and having a bunch of
.tiff's) I ran this:

>>gdalbuildvrt -srcnodata "230 245 255" tif_index.vrt *.tif
0...10...20...30...40...50...60...70...80...90...100 - done.

then

>> gdal_merge -o merged_result.tif *.vrt

and got

ERROR 4: `*.vrt' does not exist in the file system,
and is not recognised as a supported dataset name.

I'm on OSGEO4W too..


On Tue, Jun 9, 2015 at 1:24 PM, <Matt.Wilkie at gov.yk.ca> wrote:

> The error is because you need to quote the argument values to keep them
> from being interpreted as filenames:
>
>         gdal_merge -n “230 245 255” ...
>
> However gdal_merge can't use different nodata values for each band. You
> need to pre-process the files before merging. This worked for me here:
>
> Create  VRT (virtual raster) file for the input file(s):
>
>         gdalbuildvrt -srcnodata "230 245 255”"  infile1.vrt  infile1.tif
>
> Then feed the .vrt's to gdal_merge:
>
>         gdal_merge -of merged_result.tif infile1.vrt infile2.vrt ...
>
>
> You may need to switch from fwtools to Osgeo4w (if on Windows) to get
> gdalbuildvrt.
>
> Cheers,
>
> --
> matt wilkie
> --------------------------------------------
> Geomatics Analyst
> Information Management and Technology
> Yukon Department of Environment
> 10 Burns Road * Whitehorse, Yukon * Y1A 4Y9
> 867-667-8133 Tel * 867-393-7003 Fax
> http://environmentyukon.gov.yk.ca/geomatics/
> --------------------------------------------
>
>
>
> -----------------------------
>
> From: fwtools-bounces at lists.maptools.org [mailto:
> fwtools-bounces at lists.maptools.org] On Behalf Of Ari Simmons
> Sent: Tuesday, June 09, 2015 12:43 PM
> To: fwtools at lists.maptools.org
> Subject: [FWTools] gdal_merge with a specific pixel value clipped/removed
>
> I have a large set of .tif files and I need to merge/mosaic them all into
> one .tif with the no-data value removed (i.e. value 230, 245, 255).
> However, when I put this in...pixel '230, 245, 255' becomes '0, 245, 255').
> I am trying to get NO PIXEL returned for 230, 245, 255. Is that possible?
> I:\TFS_6\trial_merge>gdal_merge.py -o test.tif -n 230 245 255 file1.tif
> file2.tif
>
> ERROR 4: `245' does not exist in the file system,
> and is not recognised as a supported dataset name.
>
> ERROR 4: `255' does not exist in the file system,
> and is not recognised as a supported dataset name.
>
> 0...10...20...30...40...50...60...70...80...90...100 - done.
>
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