/*  qdfilt -- quick and dirty image sharpening and smoothing

    Copyright (C) 1997  David Flater.

    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 2 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.

    If you cannot find a copy of the GNU General Public License,
    write to the Free Software Foundation, Inc., 675 Mass Ave,
    Cambridge, MA 02139, USA.

    Description
    -----------

    This program follows in the footsteps of qdgamma in re-inventing
    the wheel for simple image processing.  This time it's linear
    filtering of the sort that could be done with pnmconvol, but
    restricted to just sharpening and smoothing.

    qdfilt version 1 works ONLY on 8-bit rawbits pixmaps and
    graymaps with maxval = 255, and ONLY on stdin and stdout.

    Usage:  qdfilt factor < input > output

    Factor     Result
    ------     ------
    <-1.0      Super extra sharpening
     -1.0      Heavy linear sharpening
     -0.2      Light linear sharpening
      0.0      No operation
      0.2      Light linear smoothing
      1.0      Max linear smoothing
     >1.0      Meaningless blurring

    Most of the time you will get better results smoothing with qdnlfilt.
    The main utility of this program is for sharpening.

    To compile:  gcc -O3 -o qdfilt qdfilt.c

    Version 2 2000-02-21
      Hastily added code to avoid choking on comments in PNM files.

    Changes from version 1.1 to 1.2:  added center pixel to mean so that
       factor of 1.0 really is max smoothing.  Need to use a slightly
       higher sharpening factor to compensate.
    Changes from version 1 to 1.1:  code cleanups.
*/

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#ifdef MSDOS
#include <io.h>
#include <fcntl.h>
#endif

unsigned char *prev, *this, *next;
int linlen;

void
usage ()
{
  fprintf (stderr, "Usage:  qdfilt factor < input > output\n\
\n\
    Factor     Result\n\
    ------     ------\n\
    <-1.0      Super extra sharpening\n\
     -1.0      Heavy linear sharpening\n\
     -0.2      Light linear sharpening\n\
      0.0      No operation\n\
      0.2      Light linear smoothing\n\
      1.0      Max linear smoothing\n\
     >1.0      Meaningless blurring\n");
  exit (-1);
}

void
bogus ()
{
  fprintf (stderr,
  "qdfilt works ONLY on 8-bit rawbits pixmaps and\n");
  fprintf (stderr,
  "graymaps with maxval = 255, and ONLY on stdin and stdout.\n");
  exit (-1);
}

int linterp (float a, float b, float x) {
  float temp;
  temp = (a + x*(b-a) + 0.5);
  if (temp < 0.0)
    temp = 0.0;
  else if (temp > 255.0)
    temp = 255.0;
  return (int)temp;
}

void
getline () {
  unsigned char *temp;
  temp = prev;
  prev = this;
  this = next;
  next = temp;
  assert (fread (next, 1, linlen, stdin) == linlen);
}

void
getnoncommentline (char buf[1000]) {
  do
    assert (fgets (buf, 1000, stdin));
  while (buf[0] == '#');
}

int
main (int argc, char **argv)
{
  int width, height, maxval, grayflag = 0, disp, x, y, mean;
  float factor;
  char magicnum[3], junk, buf[1000];
  if (argc != 2)
    usage ();
  if (sscanf (argv[1], "%f", &factor) != 1)
    usage ();
#ifdef MSDOS
  setmode (fileno (stdin), O_BINARY);
  setmode (fileno (stdout), O_BINARY);
#endif

  getnoncommentline (buf);
  if (sscanf (buf, "%2s", magicnum) != 1) {
    fprintf (stderr, "Error getting header data\n");
    bogus();
  }
  getnoncommentline (buf);
  if (sscanf (buf, "%d %d", &width, &height) != 2) {
    fprintf (stderr, "Error getting header data\n");
    bogus();
  }
  getnoncommentline (buf);
  if (sscanf (buf, "%d", &maxval) != 1) {
    fprintf (stderr, "Error getting header data\n");
    bogus();
  }
  if (strcmp (magicnum, "P5") != 0 && strcmp (magicnum, "P6") != 0) {
    fprintf (stderr, "Bad magic number\n");
    bogus ();
  }
  if (maxval != 255) {
    fprintf (stderr, "Maxval != 255\n");
    bogus ();
  }

  if (magicnum[1] == '5')
    grayflag = 1;
  printf ("%s\n%d %d\n%d\n", magicnum, width, height, maxval);

  if (width < 3 || height < 3) {
    /* Too small to do anything with; echo stdin to stdout */
    int tval;
    while ((tval = getchar ()) != EOF)
      assert (putchar (tval) != EOF);
    fflush (stdout);
    exit (0);
  }

  disp = (grayflag? 1 : 3);
  linlen = width * disp;
  assert (prev = malloc (linlen));
  assert (this = malloc (linlen));
  assert (next = malloc (linlen));

  getline();
  getline();

  assert (fwrite (this, 1, linlen, stdout) == linlen);
  for (y=1; y<height-1; y++) {
    getline();
    for (x=0; x<disp; x++)
      assert (putchar ((int)(this[x])) != EOF);
    for (x=disp; x<linlen-disp; x++) {
        mean = prev[x-disp] + this[x-disp] + next[x-disp]
             + prev[x]      + this[x]      + next[x]
             + prev[x+disp] + this[x+disp] + next[x+disp];
        assert (putchar (linterp ((float)(this[x]), (float)mean / 9.0,
          factor)) != EOF);
    }
    for (x=linlen-disp; x<linlen; x++)
      assert (putchar ((int)(this[x])) != EOF);
  }
  assert (fwrite (next, 1, linlen, stdout) == linlen);

  fflush (stdout);
  exit (0);
}