Library demo - inspecting neighbors (GNU Astronomy Utilities)

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12.4.2 Library demo - inspecting neighbors ¶

The following simple program shows how you can inspect the neighbors of a pixel using the GAL_DIMENSION_NEIGHBOR_OP function-like macro that was introduced in Dimensions (dimension.h). For easy linking/compilation of this program along with a first run see BuildProgram. Before running, also change the file name and HDU (first and second arguments to gal_fits_img_read_to_type) to specify an existing FITS file and/or extension/HDU.

To encourage good coding practices, this script contains a copyright notice with a place holder for your name and your email (as you customize it for your own purpose). Always keep a one-line description and copyright notice like this in all your scripts, such “metadata” is very important to accompany every source file you write. Of course, when you write the source file from scratch and just learn how to use a single function from this manual, only your name/year should appear. The existing name of the original author of this example program is only for cases where you copy-paste this whole file.

/* Reading a FITS image into memory.
 *
 * The following simple program shows how you can inspect the neighbors
 * of a pixel using the GAL_DIMENSION_NEIGHBOR_OP function-like macro.
 *
 * Copyright (C) 2024      Your Name <your@email.address>
 * Copyright (C) 2020-2024 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdio.h>
#include <stdlib.h>

#include <gnuastro/fits.h>
#include <gnuastro/dimension.h>

int
main(void)
{
  double sum;
  float *array;
  size_t i, num, *dinc;
  gal_data_t *input=gal_fits_img_read_to_type("input.fits", "1",
                                              GAL_TYPE_FLOAT32, -1, 1,
                                              NULL);

  /* To avoid the `void *' pointer and have `dinc'. */
  array=input->array;
  dinc=gal_dimension_increment(input->ndim, input->dsize);

  /* Go over all the pixels. */
  for(i=0;i<input->size;++i)
    {
      num=0;
      sum=0.0f;
      GAL_DIMENSION_NEIGHBOR_OP( i, input->ndim, input->dsize,
                                 input->ndim, dinc,
                                 {++num; sum+=array[nind];} );
      printf("%zu: num: %zu, sum: %f\n", i, num, sum);
    }

  /* Clean up and return. */
  gal_data_free(input);
  free(dinc);
  return EXIT_SUCCESS;
}