Open a FITS file and retrieve the first plane of the image array as a TImage object
Author: Claudi Martinez
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Friday, March 24, 2023 at 10:52 AM.
Here we open a FITS file that contains only the primary HDU, consisting on an image. The object you will see is a snapshot of the NGC7662 nebula, which was taken by the author on November 2009 in Barcelona.
TString dir = gROOT->GetTutorialDir();
Open primary HDU from file
TFITSHDU hdu(dir + "/fitsio/sample1.fits");
Dump the HDUs within the FITS file and also their metadata printf("Press ENTER to see summary of all data stored in the file:"); getchar();
Here we get the exposure time.
printf("Exposure time = %s\n", hdu.GetKeywordValue("EXPTIME").Data());
Read the primary array as a matrix, selecting only layer 0. This function may be useful to do image processing, e.g. custom filtering
std::unique_ptr<TMatrixD> mat(hdu.ReadAsMatrix(0)); mat->Print();
Read the primary array as an image, selecting only layer 0.
TImage * im = (TImage *)hdu.ReadAsImage(0);
Read the primary array as a histogram. Depending on array dimensions, the returned histogram will be 1D, 2D or 3D.
TH1 * hist = (TH1 *)hdu.ReadAsHistogram(); auto c = new TCanvas("c1", "FITS tutorial #1", 1400, 800); c->Divide(2, 1); c->cd(1); im->Draw(); c->cd(2); hist->Draw("COL");
Draw all canvases