CCfits - HEASARC - NASA

6 Writing Primary Images and Image Extensions 14
long nelements(1);
// Find the total size of the array.
// this is a little fancier than necessary ( It’s only
// calculating naxes[0]*naxes[1]) but it demonstrates use of the
// C++ standard library accumulate algorithm.
nelements = std::accumulate(&naxes[0],&naxes[naxis],1,std::multiplies
());
// create a new image extension with a 300x300 array containing float data.
std::vector extAx(2,300);
string newName ("NEW-EXTENSION");
ExtHDU* imageExt = pFits->addImage(newName,FLOAT_IMG,extAx);
// create a dummy row with a ramp. Create an array and copy the row to
// row-sized slices. [also demonstrates the use of valarray slices].
// also demonstrate implicit type conversion when writing to the image:
// input array will be of type float.
std::valarray row(vectorLength);
for (long j = 0; j < vectorLength; ++j) row[j] = j;
std::valarray array(nelements);
for (int i = 0; i < numberOfRows; ++i)
{
array[std::slice(vectorLength*static_cast(i),vectorLength,1)] =
row + i;
}
// create some data for the image extension.
long extElements = std::accumulate(extAx.begin(),extAx.end(),1,
std::multiplies());
std::valarray ranData(extElements);
const float PIBY (M_PI/150.);
for ( int jj = 0 ; jj < extElements ; ++jj)
{
float arg = PIBY*jj;
ranData[jj] = std::cos(arg);
}
long
fpixel(1);
// write the image extension data: also demonstrates switching between
// HDUs.
imageExt->write(fpixel,extElements,ranData);
//add two keys to the primary header, one long, one complex.
long exposure(1500);
std::complex omega(std::cos(2*M_PI/3.),std::sin(2*M_PI/3));
pFits->pHDU().addKey("EXPOSURE", exposure,"Total Exposure Time");
pFits->pHDU().addKey("OMEGA",omega," Complex cube root of 1 ");
// The function PHDU& FITS::pHDU() returns a reference to the object
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