Raster → Basic I/O

Each raster is composed by one or more bands, and each band has its own pixel values. If the pixel positions are not necessary when accessing the raster, the Iterators can be used instead.

When the user needs to know basic information about one raster, the method toString() can be used:

// load the input image
std::map<std::string, std::string> rinfo;
rinfo["URI"] = "input.tif";
te::rst::Raster* rin = te::rst::RasterFactory::open(rinfo);
 
// display information about raster
std::cout << rin->toString();
 
// clean up
delete rin;

The output will be:

Raster Name......: input.tif
Number of Columns: 369
Number of Rows...: 351
Number of Bands..: 3
SRID.............: 29181
Resolution in X..: 20
Resolution in Y..: 20
Extent UR........: 777957, 7.37011e+06
Extent LL........: 770597, 7.36311e+06

Band: 0 
  Min Values...: (15,0)
  Max Values...: (255,0)
  Mean Values..: (134.406,0)
  Std Values...: (46.0585,0)
  Gain values..: (1,0)
  Offset values: (0,0)

Band: 1 
  Min Values...: (61,0)
  Max Values...: (255,0)
  Mean Values..: (209.62,0)
  Std Values...: (29.6003,0)
  Gain values..: (1,0)
  Offset values: (0,0)

Band: 2 
  Min Values...: (10,0)
  Max Values...: (255,0)
  Mean Values..: (148.682,0)
  Std Values...: (36.1113,0)
  Gain values..: (1,0)
  Offset values: (0,0)

The following methods can be used to retrieve the pixel values from a specific band:

double pixel; // when using complex pixels, can use std::complex<double> pixel;
const unsigned int line = 10,
                   column = 20;
                   band = 3;
 
te::rst::Raster* myraster = ...
 
// using the raster interface
myraster->getValue(line, column, pixel, band);
 
// using the [] operator
myraster[band]->getValue(line, column, pixel);
 
// using the band interface
te::rst::Band* myband = myraster->getBand(band);
 
myband->getValue(line, column, pixel);
 
// using a vector of pixel values from the same line/column
std::vector<double> pixels;
 
myraster->getValues(line, column, pixels);
 
pixel = pixels[band];

To change values in a raster, the a similar method is used, however the raster access policy must be set to WAccess or RWAccess.

const double pixel = 125.0; // when using complex pixels, can use std::complex<double> pixel(125.0, 23.5);
const unsigned int line = 10,
                   column = 20;
                   band = 3;
 
te::rst::Raster* myraster = ...
 
// using the raster interface
myraster->setValue(line, column, pixel, band);
 
// using the [] operator
myraster[band]->setValue(line, column, pixel);
 
// using the band interface
te::rst::Band* myband = myraster->getBand(band);
 
myband->setValue(line, column, pixel);
 
// using a vector of pixel values from the same line/column
std::vector<double> pixels(myraster->getNumberOfBands());
 
pixels[band] = pixel;
 
myraster->setValues(line, column, pixels);

Internally, each band is accessed by blocks of contiguous pixels. When the user needs to have a faster access to pixel values, this option can be used. The following example shows how to copy a block of pixels from one input band to an output band, assuming both bands have the same block configuration and data types.

void te::rst::Copy(const te::rst::Band& bin, te::rst::Band& bout)
{
// create a block of pixels using the method getBlockSize() from the band
  unsigned char* buffer = new unsigned char[bin.getBlockSize()];
 
// the number of blocks in both directions (x and y)
  const int nblocksx = bin.getProperty()->m_nblocksx,
            nblocksy = bin.getProperty()->m_nblocksy;
 
// use methods read/write to copy the entire blocks
  for(int y = 0; y < nblocksy; ++y)
    for(int x = 0; x < nblocksx; ++x)
    {
      bin.read(x, y, buffer);
      bout.write(x, y, buffer);
    }
 
//clean up
  delete [] buffer;
}