[gdal-dev] Fwd: How to reuse memory pointer of GDAL Memory driver
Even Rouault
even.rouault at spatialys.com
Mon Jun 6 07:10:50 PDT 2016
See comments inline below
>
> The code:
>
>
> GDALDriver *poDriver =
> GetGDALDriverManager()->GetDriverByName(pszFormat);
>
>
> if(!poDriver)
>
> {
>
> std::cerr << "Driver " << pszFormat << " couldn't be loaded."
> << std::endl;
>
> return -4;
>
> }
>
>
> poDstDS = poDriver->Create(
> auxfilepath.string().c_str(),(int)width, (int)height,
>
> numbands, GDT_Byte, papszOptions);
--> numbands should be replaced by 0, since you add the bands afterwards
>
>
> if(poDstDS == NULL)
>
> {
>
>
> std::cerr << "Failure when creating output orthoimage " << auxfilepath <<
> std::endl;
>
> return -5;
>
> }
>
>
> if(filepath.extension() == ".jpg")
>
> {
>
> char **papszOptions2 = NULL;
>
> for(unsigned int b = 0; b < RGBRasterBands::NUMBANDS; b++)
>
> {
>
> char* opts = (char*) malloc(1024);
>
> sprintf(opts, "%p",&abyRasters[b]);
For portability, rather use CPLPrintPointer( char *pszBuffer, void *pValue, int
nMaxLen ). See https://svn.osgeo.org/gdal/trunk/gdal/frmts/vrt/vrtdriver.cpp
for an example how to use it
>
> papszOptions2 = CSLSetNameValue( papszOptions2,
> "DATAPOINTER", opts );
>
> poDstDS->AddBand(GDT_Byte, papszOptions2);
Missing CSLDestroy(papszOptions2)
>
> free(opts);
>
> }
>
> }
>
>
> //jpeg write test:
>
> char **papszOptions2 = NULL;
>
> papszOptions2 = CSLSetNameValue( papszOptions2, "QUALITY", "40" );
>
> std::cout << "Copying to " << filepath << std::endl;
>
> GDALDriver* jpegDriver =
> GetGDALDriverManager()->GetDriverByName("JPEG");
>
> GDALDataset* jpeg_ds =
> jpegDriver->CreateCopy(filepath.string().c_str(), poDstDS, false,
> papszOptions2, GDALDummyProgress, NULL);
Missing CSLDestroy(papszOptions2)
>
> if(jpeg_ds == NULL)
>
> {
>
> std::cout << "Failure when creating output orthoimage " <<
> filepath << std::endl;
>
> return -5;
>
> }
>
>
>
> On Mon, Jun 6, 2016 at 2:58 PM, Even Rouault <even.rouault at spatialys.com>
>
> wrote:
> > On Monday 06 June 2016 14:53:46 Pol Monsó Purtí wrote:
> > > Let's jump to particulars, at the end, the code.
> > >
> > > If I set the DATAPOINTER to NULL the program crashes at CreateCopy with
> > > access violation. Same if I set it to the datapointer to &abyRaster[0]
> >
> > and
> >
> > > add the remaining two bands.
> >
> > Use the Create() method of GDALDriver with 0 bands and no options. I'm not
> > sure how Open() and AddBand() play together.
> >
> > > The abyRasters are initialized to white color with memset. SO this piece
> >
> > of
> >
> > > code should give me a white jpg square of widthxheight. I could set a
> > > complete MWE if necessary.
> > >
> > > And, the code:
> > > char* filename = (char*) malloc(1024);
> > >
> > > sprintf(filename,
> >
> > "MEM:::DATAPOINTER=%p,PIXELS=%d,LINES=%d,BANDS=0",
> >
> > > NULL, width, height);
> > >
> > > poDstDS = (GDALDataset *) GDALOpen(filename,GA_Update);
> > >
> > >
> > > free(filename);
> > >
> > >
> > > for(unsigned int b = 0; b < RGBRasterBands::NUMBANDS; b++)
> > >
> > > {
> > >
> > > //assert(sizeof(long) == sizeof(void*));
> > >
> > > const void * address = static_cast<const
> >
> > void*>(&abyRasters[b]);
> >
> > > std::stringstream ss;
> > >
> > > ss << address;
> > >
> > > const char * datapointer = ss.str().c_str();
> > >
> > > std::cout << "datapointer: " << datapointer << std::endl;
> > >
> > > papszOptions = CSLSetNameValue( papszOptions,
> > >
> > > "DATAPOINTER", datapointer );
> > >
> > > poDstDS->AddBand(GDT_Byte, papszOptions);
> > >
> > > }
> > >
> > > char **papszOptions2 = NULL;
> > >
> > > papszOptions2 = CSLSetNameValue( papszOptions2, "QUALITY", "40"
> >
> > );
> >
> > > std::cout << "Copying to " << filepath << std::endl;
> > >
> > > GDALDriver* jpegDriver =
> > >
> > > GetGDALDriverManager()->GetDriverByName("JPEG");
> > >
> > > GDALDataset* jpeg_ds =
> > >
> > > jpegDriver->CreateCopy(filepath.string().c_str(), poDstDS, false,
> > > papszOptions2, GDALDummyProgress, NULL);
> > >
> > > if(jpeg_ds == NULL)
> > >
> > > {
> > >
> > > std::cout << "Failure when creating output orthoimage " <<
> > >
> > > filepath << std::endl;
> > >
> > > return -5;
> > >
> > > }
> > >
> > > The abyRasters are allocated with
> > >
> > > for(int b = 0; b < RGBRasterBands::NUMBANDS; b++)
> > > {
> > >
> > > abyRasters.push_back(new
> > >
> > > GByte[rasterMemoryDimensions.width*rasterMemoryDimensions.height]());
> >
> > memset(&abyRasters[b][0],QuickDrop::NODATAVALUE,sizeof(GByte)*rasterMemory
> > D
> >
> > > imensions.width*rasterMemoryDimensions.height); }
> > >
> > >
> > > On Mon, Jun 6, 2016 at 12:35 PM, Pol Monsó Purtí <lluna.nova at gmail.com>
> > >
> > > wrote:
> > > > Just one more question,
> > > >
> > > > If i set the option BAND=0, what should the DATAPOINTER be? Does it
> >
> > become
> >
> > > > optional?
> > > >
> > > > Cheers
> > > >
> > > > On Mon, Jun 6, 2016 at 10:55 AM, Even Rouault <
> >
> > even.rouault at spatialys.com>
> >
> > > > wrote:
> > > >> On Monday 06 June 2016 10:45:47 Pol Monsó Purtí wrote:
> > > >> > THanks Mateusz,
> > > >> >
> > > >> > You're right. I'm trying it as we speak.
> > > >> >
> > > >> > In my case I have a std::vector<GByte*> of the 3 bands, where the
> > > >> > GByte*
> > > >> > are allocated in the heap with new GByte[width*height]. I guess
> > > >> > that
> > > >>
> > > >> won't
> > > >>
> > > >> > work because the three bands have to be one single memory chunk, am
> >
> > I
> >
> > > >> > right? I guess the only solution is to switch to single band float
> >
> > and
> >
> > > >> > merge rgb to float. I'd prefer not having to refactor the rest of
> >
> > the
> >
> > > >> code.
> > > >>
> > > >> > Is it possible to have a different address for each band?
> > > >>
> > > >> Yes, create a dataset with 0 band and then add each band with the
> > > >> GDALDataset::AddBand() method
> > > >>
> > > >> See http://gdal.org/frmt_mem.html :
> > > >> """The MEM format is one of the few that supports the AddBand()
> >
> > method.
> >
> > > >> The
> > > >> AddBand() method supports DATAPOINTER, PIXELOFFSET and LINEOFFSET
> >
> > options
> >
> > > >> to
> > > >> reference an existing memory array."""
> > > >>
> > > >> > All this is to support jpg as output. All the operations are done
> >
> > in my
> >
> > > >> > GByte array and it's only at the end that I create the dataset and
> > > >>
> > > >> image.
> > > >>
> > > >> > At the moment I create a Tiff and finally createcopy to jpg.
> > > >> >
> > > >> > On Fri, Jun 3, 2016 at 9:10 PM, Mateusz Loskot <mateusz at loskot.net>
> > > >>
> > > >> wrote:
> > > >> > > On 3 June 2016 at 20:45, Pol Monsó Purtí <lluna.nova at gmail.com>
> > > >>
> > > >> wrote:
> > > >> > > > I've seen this mysterious article
> >
> > http://www.gdal.org/frmt_mem.html
> >
> > > >> > > which
> > > >> > >
> > > >> > > > references the `DATAPOINTER` option. I've seen another
> > > >> > > > reference
> > > >> > > > [here](
> >
> > https://lists.osgeo.org/pipermail/gdal-dev/2006-November/010583.html)
> >
> > > >> > > > which does
> >
> > sprintf(filename,"MEM:::DATAPOINTER=%d,PIXELS=%d,LINES=%d,BANDS=1,DATATYP
> >
> > > >> E
> >
> > =%d,PIXELOFFSET=0,LINEOFFSET=0,BANDOFFSET=0",datpt,pixels,lines,datatype)
> >
> > > >> ;>
> > > >>
> > > >> > > > dataset = GDALOpen(filename,GA_Update);
> > > >> > > >
> > > >> > > > How would this translate to c++?
> > > >> > >
> > > >> > > The line above is valid C++, isn't it.
> > > >> > > If you followed to Frank's answer [1], you'd see it slightly
> > > >> > > corrected
> > > >> > > but the technique remains the same.
> > > >> > >
> > > >> > > [1]
> > > >>
> > > >> https://lists.osgeo.org/pipermail/gdal-dev/2006-November/010603.html
> > > >>
> > > >> > > Best regards,
> > > >> > > --
> > > >> > > Mateusz Loskot, http://mateusz.loskot.net
> > > >>
> > > >> --
> > > >> Spatialys - Geospatial professional services
> > > >> http://www.spatialys.com
> >
> > --
> > Spatialys - Geospatial professional services
> > http://www.spatialys.com
--
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