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

[Paul Mallas]

Yes, I get a segmentation fault with this

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,