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

[Ari Simmons]

Matt

Not sure I see how...

    <ComplexSource>
      <SourceFilename relativeToVRT="1">TEX_N00E006.tif</SourceFilename>
      <SourceBand>1</SourceBand>
      <SourceProperties RasterXSize="1200" RasterYSize="1200"
DataType="Byte" BlockXSize="1200" BlockYSize="2" />
      <SrcRect xOff="0" yOff="0" xSize="1200" ySize="1200" />
      <DstRect xOff="0" yOff="0" xSize="1200" ySize="1200" />
      <NODATA>230</NODATA>

Do you mean change

 <NODATA>230</NODATA>

to

 <NODATA>230 245 255</NODATA>

On Wed, Jun 10, 2015 at 10:20 AM, <Matt.Wilkie at gov.yk.ca> wrote:

>  Perhaps try editing the .vrt file with a text editor and changing the
> nodata value by hand?
>
>
>
> Matt
>
>
>
> *From:* fwtools-bounces at lists.maptools.org [mailto:
> fwtools-bounces at lists.maptools.org] *On Behalf Of *Ari Simmons
> *Sent:* Wednesday, June 10, 2015 10:19 AM
> *To:* Chaitanya kumar CH
> *Cc:* fwtools at lists.maptools.org
> *Subject:* Re: [FWTools] gdal_merge with a specific pixel value
> clipped/removed
>
>
>
> 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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