Hello to all gdal community members,
I had a very basic question, but I couldn't find a proper answer anywhere in
the forums or mailing lists, even on the official tutorials like:
https://gdal.org/tutorials/raster_api_tut.html
So my simple question is how to handle properly a "generic" data type (i.e.
known only at runtime) when reading a raster dataset from an image.
So far I could use properly GetRasterDataType / RasterIO to read my data, but I
always have to specify in my code the actual data type (ex uint16_t).
The best workaround that I could find is, first read the dataset as "raw"
binary data (i.e. type=uint8_t) then "interpret" it to the proper actual type
(ex uint16_t).
But this is still a heavy solution and moreover during the data interpretation
I could not avoid a copy of the complete dataset !
Even my attemps to use templates did not help much because they only apply to
functions (not variables or members) and don't really solve the problem.
So to sum up I would like to:
1) open an image (e.g. a tiff image with 1 single band) WITHOUT knowing its
data type beforehand
2) store the raster dataset in a variable of any kind, WITHOUT making copy or
type cast (I mean involving math operations ) !
3) easily find and print some values (ex: image[0;0])
I will appreciate any answer on this subject !
Thank you all.
Jérôme Moré.
PS: I included my current code in a separate file.
Envoyé à partir d’Outlook<http://aka.ms/weboutlook>
// g++ gdal_mwe.cpp -o gdal_mwe -I /usr/include/gdal -l gdal
#include <iostream>
#include "gdal_priv.h"
#include <time.h>
using namespace std;
// ----------------------------------------------------------------------
class gdalImage {
private:
string path;
int width;
int height;
int bandCount;
GDALDataType dataType;
int dataTypeSizeBytes;
GDALDataset* gdalDataset;
vector<uint8_t> pixelBytes;
public:
void read (string path);
template <typename pixelT>
void displayTemplate ();
void display ();
};
// ----------------------------------------------------------------------
void gdalImage::read (string p)
{
path = p;
gdalDataset = (GDALDataset*) GDALOpen (path.c_str (), GA_ReadOnly);
width = gdalDataset->GetRasterXSize ();
height = gdalDataset->GetRasterYSize ();
bandCount = gdalDataset->GetRasterCount ();
GDALRasterBand &poBand = *gdalDataset->GetRasterBand (1);
dataType = poBand.GetRasterDataType ();
dataTypeSizeBytes = GDALGetDataTypeSizeBytes(dataType);
pixelBytes.resize (width*height*bandCount*dataTypeSizeBytes);
CPLErr err = poBand.RasterIO (GF_Read, 0, 0, width, height,
&pixelBytes[0], width, height, dataType, 0, 0); //ok juste
// CPLErr err = poBand.RasterIO (GF_Read, 0, 0, width, height,
// &pixelBytes[0], width, height, GDT_Byte, 0, 0);
}
// ----------------------------------------------------------------------
template <typename pixelT>
void gdalImage::displayTemplate ()
{
cout << "image: " << path << endl;
cout << " dimensions: ";
cout << width << " x " << height << " x " << bandCount << " bands";
cout << ", type: " << dataType;
cout << " (size " << dataTypeSizeBytes << " Bytes)" << endl;
cout << " nb of bytes: " << pixelBytes.size() << endl;
// vector<uint16_t> pixels (&pixelBytes[0], &pixelBytes[0] + width*height*bandCount);
vector<pixelT> pixels (width*height*bandCount);
memcpy ( &pixels[0], &pixelBytes[0], pixelBytes.size() );
for (int k=0; k<width*height && k<10*10; k++)
{
// cout << 0+pixelBytes[k] << " ";
cout << 0+pixels[k] << " ";
if ((k+1)%width==0)
cout << endl;
}
cout << endl;
// for (int w=0; w<width && w<10; w++)
// {
// for (int h=0; h<height && h<10; h++)
// cout << 0+pixelBytes[w + width*h] << " ";
// cout << endl;
// }
}
// ----------------------------------------------------------------------
void gdalImage::display ()
{
switch (dataType)
{
case GDT_Byte: displayTemplate<uint8_t>(); break;
case GDT_UInt16: displayTemplate<uint16_t>(); break;
case GDT_Int16: displayTemplate<int16_t>(); break;
case GDT_UInt32: displayTemplate<uint32_t>(); break;
case GDT_Int32: displayTemplate<int32_t>(); break;
case GDT_Float32: displayTemplate<float>(); break;
case GDT_Float64: displayTemplate<double>(); break;
default: break;
}
}
// ----------------------------------------------------------------------
int main()
{
GDALAllRegister ();
// string path = "/media/jerome/Data/Images/datatypes/4x4_Byte.tif";
// string path = "/media/jerome/Data/Images/datatypes/4x4_UInt16_sc.tif";
// string path = "/media/jerome/Data/Images/datatypes/4x4_Int16.tif";
// string path = "/media/jerome/Data/Images/datatypes/4x4_UInt32.tif";
// string path = "/media/jerome/Data/Images/datatypes/4x4_Int32.tif";
// string path = "/media/jerome/Data/Images/arles.tif";
string path = "/media/jerome/Data/Images/IMG_L2A_TOA_20181025_a20181005T104652_pSPOT6_mMS.TIF";
// gdalImage <uint16_t> gim;
gdalImage gim;
gim.read (path);
// gim.displayTemplate<uint16_t>();
gim.display();
}
// ----------------------------------------------------------------------
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