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

[Ari Simmons]

Ok - so gdal_translate works great! Thanks!

HOWEVER, the removal of value 230 245 255 is still no happening...when I
put in:


>>gdalbuildvrt -srcnodata "230 245 255" tif_index.vrt *.tif

I get a .vrt with Band 1 = 0 (instead of 230) and the full 3 Band value
becoming (0 245 255)....not what I expected. I expected it to become
"NoData"....


On Tue, Jun 9, 2015 at 9:17 PM, Chaitanya kumar CH <chaitanya.ch at gmail.com>
wrote:

> Ari,
>
> The vrt is an xml file that represents a single raster dataset made up of
> one or many rasters. So, it is already merged. You can read it using any
> good text editor.
> You only have to run gdal_translate to convert it to a tif.
>
> gdal_translate -of GTiff tif_index.vrt tif_index.tif
>
> On Wed, Jun 10, 2015 at 2:40 AM Ari Simmons <ari.ucb.fire at gmail.com>
> wrote:
>
>> 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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>>
> --
>
> Chaitanya Kumar CH
>
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