File: iter_image.c

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#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include "fitsio.h"

/*
  This program illustrates how to use the CFITSIO iterator function.
  It reads and modifies the input 'iter_image.fit' image file by setting
  all the pixel values to zero (DESTROYING THE ORIGINAL IMAGE!!!)
*/
main()
{
    extern zero_image(); /* external work function is passed to the iterator */
    fitsfile *fptr;
    iteratorCol cols[3];  /* structure used by the iterator function */
    int n_cols;
    long rows_per_loop, offset;

    int status, nkeys, keypos, hdutype, ii, jj;
    char filename[]  = "iter_image.fit";     /* name of rate FITS file */

    status = 0; 

    fits_open_file(&fptr, filename, READWRITE, &status); /* open file */


    n_cols = 1;

    /* define input column structure members for the iterator function */
    fits_iter_set_file(&cols[0], fptr);
    fits_iter_set_iotype(&cols[0], InputOutputCol);
    fits_iter_set_datatype(&cols[0], 0);

    rows_per_loop = 0;  /* use default optimum number of rows */
    offset = 0;         /* process all the rows */

    /* apply the rate function to each row of the table */
    printf("Calling iterator function...%d\n", status);

    fits_iterate_data(n_cols, cols, offset, rows_per_loop,
                      zero_image, 0L, &status);

    fits_close_file(fptr, &status);      /* all done */

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

    return(status);
}
/*--------------------------------------------------------------------------*/
int zero_image(long totalrows, long offset, long firstrow, long nrows,
             int ncols, iteratorCol *cols, void *user_strct ) 

/*
   Sample iterator function that calculates the output flux 'rate' column
   by dividing the input 'counts' by the 'time' column.
   It also applies a constant deadtime correction factor if the 'deadtime'
   keyword exists.  Finally, this creates or updates the 'LIVETIME'
   keyword with the sum of all the individual integration times.
*/
{
    int ii, status = 0;

    /* declare variables static to preserve their values between calls */
    static int *counts;

    /*--------------------------------------------------------*/
    /*  Initialization procedures: execute on the first call  */
    /*--------------------------------------------------------*/
    if (firstrow == 1)
    {
       if (ncols != 1)
           return(-1);  /* number of columns incorrect */

       /* assign the input pointers to the appropriate arrays and null ptrs*/
       counts       = (int *)  fits_iter_get_array(&cols[0]);
    }

    /*--------------------------------------------*/
    /*  Main loop: process all the rows of data */
    /*--------------------------------------------*/

    /*  NOTE: 1st element of array is the null pixel value!  */
    /*  Loop from 1 to nrows, not 0 to nrows - 1.  */

    for (ii = 1; ii <= nrows; ii++)
    {
       counts[ii] = 1.;
    }
    printf("firstrows, nrows = %d %d\n", firstrow, nrows);
    
    return(0);  /* return successful status */
}