2.6 Example Program

The following listing shows an example of how to use the CFITSIO routines in a C program. Refer to the cookbook.c program that is included with the CFITSIO distribution for other example routines.

This program creates a new FITS file, containing a FITS image. An `EXPOSURE' keyword is written to the header, then the image data are written to the FITS file before closing the FITS file.

#include "fitsio.h"  /* required by every program that uses CFITSIO  */
    fitsfile *fptr;       /* pointer to the FITS file; defined in fitsio.h */
    int status, ii, jj;
    long  fpixel = 1, naxis = 2, nelements, exposure;
    long naxes[2] = { 300, 200 };   /* image is 300 pixels wide by 200 rows */
    short array[200][300];

    status = 0;         /* initialize status before calling fitsio routines */
    fits_create_file(&fptr, "testfile.fits", &status);   /* create new file */

    /* Create the primary array image (16-bit short integer pixels */
    fits_create_img(fptr, SHORT_IMG, naxis, naxes, &status);

    /* Write a keyword; must pass the ADDRESS of the value */
    exposure = 1500.;
    fits_update_key(fptr, TLONG, "EXPOSURE", &exposure,
         "Total Exposure Time", &status);

    /* Initialize the values in the image with a linear ramp function */
    for (jj = 0; jj < naxes[1]; jj++)
        for (ii = 0; ii < naxes[0]; ii++)
            array[jj][ii] = ii + jj;

    nelements = naxes[0] * naxes[1];          /* number of pixels to write */

    /* Write the array of integers to the image */
    fits_write_img(fptr, TSHORT, fpixel, nelements, array[0], &status);

    fits_close_file(fptr, &status);            /* close the file */

    fits_report_error(stderr, status);  /* print out any error messages */
    return( status );