[gdal-dev] Re: Transposing image data using RasterIO

[Paul Mallas]

Oh yes, I checked those several ties.

While I was not able to read lines then write columns, I am having 
better luck reading columns then writing lines.

But, Frank seemed to think that the software might be inefficient 
accessing columns.  He certainly was right - glacier creep is faster 
this.  I will have to come up with something else, but it certianly has 
been a learning experience.

On 6/22/2011 9:51 AM, Chaitanya kumar CH wrote:
> Paul,
>
> Please check that you used the right values for XSize and YSize.
>
> On Wed, Jun 22, 2011 at 6:39 PM, Paul Mallas <pmallas at rsmas.miami.edu
> <mailto:pmallas at rsmas.miami.edu>> wrote:
>
>     Yes, I tried this. I keep getting a segmentation fault doing it this
>     way.
>
>     I will dig further, maybe something else is not right.
>
>     Regards,
>     Paul
>
>
>     On 6/17/2011 6:25 PM, Paul Mallas wrote:
>
>         On 6/17/2011 5:41 PM, Frank Warmerdam wrote:
>
>             On 11-06-17 03:23 PM, Paul Mallas wrote:
>
>                 Hello,
>
>                 I am trying to transpose image data (i.e., swap lines
>                 and columns)
>                 and am
>                 struggling to make it work properly. I think this should
>                 be possible
>                 through
>                 RasterIO, but so far no luck. Any suggestions?
>
>                 My approach so far has been like this, with image nXsize
>                 by nYsize:
>
>                 void *pData = VSIMalloc2(nXSize,
>                 (GDALGetDataTypeSize(eType) / 8));
>
>                 for (int iLine = 0; iLine < nYSize; iLine++) {
>
>                 // Read in row (line)
>                 eErr = poSrcBand->RasterIO(GF_Read, 0, iLine, nXSize, 1,
>                 pData,
>                 nXSize, 1, eType, 0,0);
>
>                 // Now I want to write a column, nothing I tried here
>                 has worked
>                 eErr = poDstBand->RasterIO(GF_Write, .......
>
>
>             Paul,
>
>             You should be able to write this column wise like:
>
>             poDstBand->RasterIO( GF_Write, iLine, 0, 1, nXSize,
>             pData, 1, nXSize, eType, 0, 0 );
>
>             Note that this can be pretty inefficient depending on the
>             format and
>             how it is blocked.
>
>             Best regards,
>
>
>         Hmm, I thought I tried this configuration. I will try again.
>         Thank you
>         for your time Frank.
>
>
>
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>
>
> --
> Best regards,
> Chaitanya kumar CH.
> /tʃaɪθənjə/ /kʊmɑr/
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>
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