about summary refs log tree commit diff
path: root/editor/pnmnlfilt.c
blob: 20705f82fc74a205e2529154a33402303e587320 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
/* pnmnlfilt.c - 4 in 1 (2 non-linear) filter
**             - smooth an anyimage
**             - do alpha trimmed mean filtering on an anyimage
**             - do optimal estimation smoothing on an anyimage
**             - do edge enhancement on an anyimage
**
** Version 1.0
**
** The implementation of an alpha-trimmed mean filter
** is based on the description in IEEE CG&A May 1990
** Page 23 by Mark E. Lee and Richard A. Redner.
**
** The paper recommends using a hexagon sampling region around each
** pixel being processed, allowing an effective sub pixel radius to be
** specified. The hexagon values are sythesized by area sampling the
** rectangular pixels with a hexagon grid. The seven hexagon values
** obtained from the 3x3 pixel grid are used to compute the alpha
** trimmed mean. Note that an alpha value of 0.0 gives a conventional
** mean filter (where the radius controls the contribution of
** surrounding pixels), while a value of 0.5 gives a median filter.
** Although there are only seven values to trim from before finding
** the mean, the algorithm has been extended from that described in
** CG&A by using interpolation, to allow a continuous selection of
** alpha value between and including 0.0 to 0.5  The useful values
** for radius are between 0.3333333 (where the filter will have no
** effect because only one pixel is sampled), to 1.0, where all
** pixels in the 3x3 grid are sampled.
**
** The optimal estimation filter is taken from an article "Converting Dithered
** Images Back to Gray Scale" by Allen Stenger, Dr Dobb's Journal, November
** 1992, and this article references "Digital Image Enhancement andNoise Filtering by
** Use of Local Statistics", Jong-Sen Lee, IEEE Transactions on Pattern Analysis and
** Machine Intelligence, March 1980.
**
** Also borrow the  technique used in pgmenhance(1) to allow edge
** enhancement if the alpha value is negative.
**
** Author:
**         Graeme W. Gill, 30th Jan 1993
**         graeme@labtam.oz.au
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation.  This software is provided "as is" without express or
** implied warranty.
*/

#include <math.h>

#include "pm_c_util.h"
#include "pnm.h"

/* MXIVAL is the maximum input sample value we can handle.
   It is limited by our willingness to allocate storage in various arrays
   that are indexed by sample values.

   We use PPM_MAXMAXVAL because that used to be the maximum possible
   sample value in the format, and most images still limit themselves to
   this value.
*/

#define MXIVAL PPM_MAXMAXVAL   

xelval omaxval; 
    /* global so that pixel processing code can get at it quickly */
int noisevariance;      
    /* global so that pixel processing code can get at it quickly */

/*
 * Declared static here rather than passing a jillion options in the call to
 * do_one_frame().   Also it makes a huge amount of sense to only malloc the
 * row buffers once instead of for each frame (with the corresponding free'ing
 * of course).
*/
static  xel *irows[3];
static  xel *irow0, *irow1, *irow2, *orow;
static  double radius=0.0,alpha= -1.0;
static  int rows, cols, format, oformat, row, col;
static  int (*atfunc)(int *);
static  xelval maxval;

#define NOIVAL (MXIVAL + 1)             /* number of possible input values */

#define SCALEB 8                                /* scale bits */
#define SCALE (1 << SCALEB)     /* scale factor */
#define MXSVAL (MXIVAL * SCALE) /* maximum scaled values */

#define CSCALEB 2                               /* coarse scale bits */
#define CSCALE (1 << CSCALEB)   /* coarse scale factor */
#define MXCSVAL (MXIVAL * CSCALE)       /* maximum coarse scaled values */
#define NOCSVAL (MXCSVAL + 1)   /* number of coarse scaled values */
#define SCTOCSC(x) ((x) >> (SCALEB - CSCALEB))  /*  scaled to coarse scaled */
#define CSCTOSC(x) ((x) << (SCALEB - CSCALEB))  /*  course scaled to scaled */

#ifndef MAXINT
# define MAXINT 0x7fffffff      /* assume this is a 32 bit machine */
#endif

/* round and scale floating point to scaled integer */
#define ROUNDSCALE(x) ((int)(((x) * (double)SCALE) + 0.5))
/* round and un-scale scaled integer value */
#define RUNSCALE(x) (((x) + (1 << (SCALEB-1))) >> SCALEB) 
/* rounded un-scale */
#define UNSCALE(x) ((x) >> SCALEB)

static double
sqr(double const arg) {
    return arg * arg;
}



/* We restrict radius to the values: 0.333333 <= radius <= 1.0 */
/* so that no fewer and no more than a 3x3 grid of pixels around */
/* the pixel in question needs to be read. Given this, we only */
/* need 3 or 4 weightings per hexagon, as follows: */
/*                  _ _                         */
/* Vertical hex:   |_|_|  1 2                   */
/*                 |X|_|  0 3                   */
/*                                       _      */
/*              _                      _|_|   1 */
/* Middle hex: |_| 1  Horizontal hex: |X|_| 0 2 */
/*             |X| 0                    |_|   3 */
/*             |_| 2                            */

/* all filters */
int V0[NOIVAL],V1[NOIVAL],V2[NOIVAL],V3[NOIVAL];        /* vertical hex */
int M0[NOIVAL],M1[NOIVAL],M2[NOIVAL];                   /* middle hex */
int H0[NOIVAL],H1[NOIVAL],H2[NOIVAL],H3[NOIVAL];        /* horizontal hex */

/* alpha trimmed and edge enhancement only */
int ALFRAC[NOIVAL * 8];                 /* fractional alpha divider table */

/* optimal estimation only */
int AVEDIV[7 * NOCSVAL];                /* divide by 7 to give average value */
int SQUARE[2 * NOCSVAL];                /* scaled square lookup table */

/* ************************************************** *
   Hexagon intersecting square area functions 
   Compute the area of the intersection of a triangle 
   and a rectangle 
   ************************************************** */

/* Triangle orientation is per geometric axes (not graphical axies) */

#define NW 0    /* North west triangle /| */
#define NE 1    /* North east triangle |\ */
#define SW 2    /* South west triangle \| */
#define SE 3    /* South east triangle |/ */
#define STH 2
#define EST 1

#define SWAPI(a,b) (t = a, a = -b, b = -t)

static double 
triang_area(double rx0, double ry0, double rx1, double ry1,
            double tx0, double ty0, double tx1, double ty1,
            int tt) {
/* rx0,ry0,rx1,ry1:       rectangle boundaries */
/* tx0,ty0,tx1,ty1:       triangle boundaries */
/* tt:                    triangle type */

    double a,b,c,d;
    double lx0,ly0,lx1,ly1;

    /* Convert everything to a NW triangle */
    if (tt & STH) {
        double t;
        SWAPI(ry0,ry1);
        SWAPI(ty0,ty1);
    }
    if (tt & EST) {
        double t;
        SWAPI(rx0,rx1);
        SWAPI(tx0,tx1);
    }
    /* Compute overlapping box */
    if (tx0 > rx0)
        rx0 = tx0;
    if (ty0 > ry0)
        ry0 = ty0;
    if (tx1 < rx1)
        rx1 = tx1;
    if (ty1 < ry1)
        ry1 = ty1;
    if (rx1 <= rx0 || ry1 <= ry0)
        return 0.0;

    /* Need to compute diagonal line intersection with the box */
    /* First compute co-efficients to formulas x = a + by and y = c + dx */
    b = (tx1 - tx0)/(ty1 - ty0);
    a = tx0 - b * ty0;
    d = (ty1 - ty0)/(tx1 - tx0);
    c = ty0 - d * tx0;
    
    /* compute top or right intersection */
    tt = 0;
    ly1 = ry1;
    lx1 = a + b * ly1;
    if (lx1 <= rx0)
        return (rx1 - rx0) * (ry1 - ry0);
    else if (lx1 > rx1) {
        /* could be right hand side */
        lx1 = rx1;
        ly1 = c + d * lx1;
        if (ly1 <= ry0)
            return (rx1 - rx0) * (ry1 - ry0);
        tt = 1; /* right hand side intersection */
    }
    /* compute left or bottom intersection */
    lx0 = rx0;
    ly0 = c + d * lx0;
    if (ly0 >= ry1)
        return (rx1 - rx0) * (ry1 - ry0);
    else if (ly0 < ry0) {
        /* could be right hand side */
        ly0 = ry0;
        lx0 = a + b * ly0;
        if (lx0 >= rx1)
            return (rx1 - rx0) * (ry1 - ry0);
        tt |= 2;        /* bottom intersection */
    }
    
    if (tt == 0) {
        /* top and left intersection */
        /* rectangle minus triangle */
        return ((rx1 - rx0) * (ry1 - ry0))
            - (0.5 * (lx1 - rx0) * (ry1 - ly0));
    } else if (tt == 1) {
        /* right and left intersection */
        return ((rx1 - rx0) * (ly0 - ry0))
            + (0.5 * (rx1 - rx0) * (ly1 - ly0));
    } else if (tt == 2) {
        /* top and bottom intersection */
        return ((rx1 - lx1) * (ry1 - ry0))
            + (0.5 * (lx1 - lx0) * (ry1 - ry0));
    } else {
        /* tt == 3 */ 
        /* right and bottom intersection */
        /* triangle */
        return (0.5 * (rx1 - lx0) * (ly1 - ry0));
    }
}



static double
rectang_area(double rx0, double ry0, double rx1, double ry1, 
             double tx0, double ty0, double tx1, double ty1) {
/* Compute rectangle area */
/* rx0,ry0,rx1,ry1:  rectangle boundaries */
/* tx0,ty0,tx1,ty1:  rectangle boundaries */

    /* Compute overlapping box */
    if (tx0 > rx0)
        rx0 = tx0;
    if (ty0 > ry0)
        ry0 = ty0;
    if (tx1 < rx1)
        rx1 = tx1;
    if (ty1 < ry1)
        ry1 = ty1;
    if (rx1 <= rx0 || ry1 <= ry0)
        return 0.0;
    return (rx1 - rx0) * (ry1 - ry0);
}




static double 
hex_area(double sx, double sy, double hx, double hy, double d) {
/* compute the area of overlap of a hexagon diameter d, */
/* centered at hx,hy, with a unit square of center sx,sy. */
/* sx,sy:    square center */
/* hx,hy,d:  hexagon center and diameter */

    double hx0,hx1,hx2,hy0,hy1,hy2,hy3;
    double sx0,sx1,sy0,sy1;

    /* compute square co-ordinates */
    sx0 = sx - 0.5;
    sy0 = sy - 0.5;
    sx1 = sx + 0.5;
    sy1 = sy + 0.5;

    /* compute hexagon co-ordinates */
    hx0 = hx - d/2.0;
    hx1 = hx;
    hx2 = hx + d/2.0;
    hy0 = hy - 0.5773502692 * d;    /* d / sqrt(3) */
    hy1 = hy - 0.2886751346 * d;    /* d / sqrt(12) */
    hy2 = hy + 0.2886751346 * d;    /* d / sqrt(12) */
    hy3 = hy + 0.5773502692 * d;    /* d / sqrt(3) */

    return
        triang_area(sx0,sy0,sx1,sy1,hx0,hy2,hx1,hy3,NW) +
        triang_area(sx0,sy0,sx1,sy1,hx1,hy2,hx2,hy3,NE) +
        rectang_area(sx0,sy0,sx1,sy1,hx0,hy1,hx2,hy2) +
        triang_area(sx0,sy0,sx1,sy1,hx0,hy0,hx1,hy1,SW) +
        triang_area(sx0,sy0,sx1,sy1,hx1,hy0,hx2,hy1,SE);
}




static void
setupAvediv(void) {

    unsigned int i;

    for (i=0; i < (7 * NOCSVAL); ++i) {
        /* divide scaled value by 7 lookup */
        AVEDIV[i] = CSCTOSC(i)/7;       /* scaled divide by 7 */
    }

}




static void
setupSquare(void) {

    unsigned int i;

    for (i=0; i < (2 * NOCSVAL); ++i) {
        /* compute square and rescale by (val >> (2 * SCALEB + 2)) table */
        int const val = CSCTOSC(i - NOCSVAL); 
        /* NOCSVAL offset to cope with -ve input values */
        SQUARE[i] = (val * val) >> (2 * SCALEB + 2);
    }
}




static void
setup1(double   const alpha,
       double   const radius,
       double   const maxscale,
       int *    const alpharangeP,
       double * const meanscaleP,
       double * const mmeanscaleP,
       double * const alphafractionP,
       int *    const noisevarianceP) {


    setupAvediv();
    setupSquare();

    if (alpha >= 0.0 && alpha <= 0.5) {
        /* alpha trimmed mean */
        double const noinmean =  ((0.5 - alpha) * 12.0) + 1.0;
            /* number of elements (out of a possible 7) used in the mean */

        *mmeanscaleP = *meanscaleP = maxscale/noinmean;
        if (alpha == 0.0) {
            /* mean filter */ 
            *alpharangeP = 0;
            *alphafractionP = 0.0;            /* not used */
        } else if (alpha < (1.0/6.0)) {
            /* mean of 5 to 7 middle values */
            *alpharangeP = 1;
            *alphafractionP = (7.0 - noinmean)/2.0;
        } else if (alpha < (1.0/3.0)) {
            /* mean of 3 to 5 middle values */
            *alpharangeP = 2;
            *alphafractionP = (5.0 - noinmean)/2.0;
        } else {
            /* mean of 1 to 3 middle values */
            /* alpha == 0.5 == median filter */
            *alpharangeP = 3;
            *alphafractionP = (3.0 - noinmean)/2.0;
        }
    } else if (alpha >= 1.0 && alpha <= 2.0) {
        /* optimal estimation - alpha controls noise variance threshold. */
        double const alphaNormalized = alpha - 1.0;
            /* normalize it to 0.0 -> 1.0 */
        double const noinmean = 7.0;
        *alpharangeP = 5;                 /* edge enhancement function */
        *mmeanscaleP = *meanscaleP = maxscale;  /* compute scaled hex values */
        *alphafractionP = 1.0/noinmean;   
            /* Set up 1:1 division lookup - not used */
        *noisevarianceP = sqr(alphaNormalized * omaxval) / 8.0;    
            /* estimate of noise variance */
    } else if (alpha >= -0.9 && alpha <= -0.1) {
        /* edge enhancement function */
        double const posAlpha = -alpha;
            /* positive alpha value */
        *alpharangeP = 4;                 /* edge enhancement function */
        *meanscaleP = maxscale * (-posAlpha/((1.0 - posAlpha) * 7.0));
            /* mean of 7 and scaled by -posAlpha/(1-posAlpha) */
        *mmeanscaleP = maxscale * (1.0/(1.0 - posAlpha) + *meanscaleP);    
            /* middle pixel has 1/(1-posAlpha) as well */
        *alphafractionP = 0.0;    /* not used */
    } else {
        /* An entry condition on 'alpha' makes this impossible */
        pm_error("INTERNAL ERROR: impossible alpha value: %f", alpha);
    }
}




static void
setupAlfrac(double const alphafraction) {
    /* set up alpha fraction lookup table used on big/small */

    unsigned int i;

    for (i=0; i < (NOIVAL * 8); ++i) {
        ALFRAC[i] = ROUNDSCALE(i * alphafraction);
    }
}




static void
setupPixelWeightingTables(double const radius,
                          double const meanscale,
                          double const mmeanscale) {

    /* Setup pixel weighting tables - note we pre-compute mean
       division here too. 
    */
    double const hexhoff = radius/2;      
        /* horizontal offset of vertical hex centers */
    double const hexvoff = 3.0 * radius/sqrt(12.0); 
        /* vertical offset of vertical hex centers */

    double const tabscale  = meanscale  / (radius * hexvoff);
    double const mtabscale = mmeanscale / (radius * hexvoff);

    /* scale tables to normalize by hexagon area, and number of
       hexes used in mean 
    */
    double const v0 =
        hex_area(0.0,  0.0, hexhoff, hexvoff, radius) * tabscale;
    double const v1 =
        hex_area(0.0,  1.0, hexhoff, hexvoff, radius) * tabscale;
    double const v2 =
        hex_area(1.0,  1.0, hexhoff, hexvoff, radius) * tabscale;
    double const v3 =
        hex_area(1.0,  0.0, hexhoff, hexvoff, radius) * tabscale;
    double const m0 =
        hex_area(0.0,  0.0, 0.0,     0.0,     radius) * mtabscale;
    double const m1 =
        hex_area(0.0,  1.0, 0.0,     0.0,     radius) * mtabscale;
    double const m2 =
        hex_area(0.0, -1.0, 0.0,     0.0,     radius) * mtabscale;
    double const h0 =
        hex_area(0.0,  0.0, radius,  0.0,     radius) * tabscale;
    double const h1 =
        hex_area(1.0,  1.0, radius,  0.0,     radius) * tabscale;
    double const h2 =
        hex_area(1.0,  0.0, radius,  0.0,     radius) * tabscale;
    double const h3 =
        hex_area(1.0, -1.0, radius,  0.0,     radius) * tabscale;

    unsigned int i;

    for (i=0; i <= MXIVAL; ++i) {
        V0[i] = ROUNDSCALE(i * v0);
        V1[i] = ROUNDSCALE(i * v1);
        V2[i] = ROUNDSCALE(i * v2);
        V3[i] = ROUNDSCALE(i * v3);
        M0[i] = ROUNDSCALE(i * m0);
        M1[i] = ROUNDSCALE(i * m1);
        M2[i] = ROUNDSCALE(i * m2);
        H0[i] = ROUNDSCALE(i * h0);
        H1[i] = ROUNDSCALE(i * h1);
        H2[i] = ROUNDSCALE(i * h2);
        H3[i] = ROUNDSCALE(i * h3);
    }
}




/* Table initialization function - return alpha range */
static int 
atfilt_setup(double const alpha,
             double const radius,
             double const maxscale) {

    int alpharange;                 /* alpha range value 0 - 5 */
    double meanscale;               /* scale for finding mean */
    double mmeanscale;              /* scale for finding mean - midle hex */
    double alphafraction;   
        /* fraction of next largest/smallest to subtract from sum */

    setup1(alpha, radius, maxscale,
           &alpharange, &meanscale, &mmeanscale, &alphafraction,
           &noisevariance);

    setupAlfrac(alphafraction);

    setupPixelWeightingTables(radius, meanscale, mmeanscale);

    return alpharange;
}



static int 
atfilt0(int * p) {
/* Core pixel processing function - hand it 3x3 pixels and return result. */
/* Mean filter */
    /* 'p' is 9 pixel values from 3x3 neighbors */
    int retv;
    /* map to scaled hexagon values */
    retv = M0[p[0]] + M1[p[3]] + M2[p[7]];
    retv += H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
    retv += V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
    retv += V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
    retv += H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
    retv += V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
    retv += V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
    return UNSCALE(retv);
}

#define CHECK(xx) {\
        h0 += xx; \
        if (xx > big) \
            big = xx; \
        else if (xx < small) \
            small = xx; }

static int 
atfilt1(int * p) {
/* Mean of 5 - 7 middle values */
/* 'p' is 9 pixel values from 3x3 neighbors */

    int h0,h1,h2,h3,h4,h5,h6;       /* hexagon values    2 3   */
                                    /*                  1 0 4  */
                                    /*                   6 5   */
    int big,small;
    /* map to scaled hexagon values */
    h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
    h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
    h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
    h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
    h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
    h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
    h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
    /* sum values and also discover the largest and smallest */
    big = small = h0;
    CHECK(h1);
    CHECK(h2);
    CHECK(h3);
    CHECK(h4);
    CHECK(h5);
    CHECK(h6);
    /* Compute mean of middle 5-7 values */
    return UNSCALE(h0 -ALFRAC[(big + small)>>SCALEB]);
}
#undef CHECK

#define CHECK(xx) {\
        h0 += xx; \
        if (xx > big1) {\
            if (xx > big0) {\
                big1 = big0; \
                big0 = xx; \
            } else \
                big1 = xx; \
        } \
        if (xx < small1) {\
            if (xx < small0) {\
                small1 = small0; \
                small0 = xx; \
                } else \
                    small1 = xx; \
        }\
    }


static int 
atfilt2(int *p) {
/* Mean of 3 - 5 middle values */
/* 'p' is 9 pixel values from 3x3 neighbors */
    int h0,h1,h2,h3,h4,h5,h6;       /* hexagon values    2 3   */
                                    /*                  1 0 4  */
                                    /*                   6 5   */
    int big0,big1,small0,small1;
    /* map to scaled hexagon values */
    h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
    h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
    h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
    h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
    h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
    h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
    h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
    /* sum values and also discover the 2 largest and 2 smallest */
    big0 = small0 = h0;
    small1 = MAXINT;
    big1 = 0;
    CHECK(h1);
    CHECK(h2);
    CHECK(h3);
    CHECK(h4);
    CHECK(h5);
    CHECK(h6);
    /* Compute mean of middle 3-5 values */
    return UNSCALE(h0 -big0 -small0 -ALFRAC[(big1 + small1)>>SCALEB]);
}

#undef CHECK

#define CHECK(xx) {\
        h0 += xx; \
        if (xx > big2) \
                { \
                if (xx > big1) \
                        { \
                        if (xx > big0) \
                                { \
                                big2 = big1; \
                                big1 = big0; \
                                big0 = xx; \
                                } \
                        else \
                                { \
                                big2 = big1; \
                                big1 = xx; \
                                } \
                        } \
                else \
                        big2 = xx; \
                } \
        if (xx < small2) \
                { \
                if (xx < small1) \
                        { \
                        if (xx < small0) \
                                { \
                                small2 = small1; \
                                small1 = small0; \
                                small0 = xx; \
                                } \
                        else \
                                { \
                                small2 = small1; \
                                small1 = xx; \
                                } \
                        } \
                else \
                        small2 = xx; \
                                         }}

static int 
atfilt3(int *p) {
/* Mean of 1 - 3 middle values. If only 1 value, then this is a median
   filter. 
*/
/* 'p' is pixel values from 3x3 neighbors */
    int h0,h1,h2,h3,h4,h5,h6;       /* hexagon values    2 3   */
                                    /*                  1 0 4  */
                                    /*                   6 5   */
    int big0,big1,big2,small0,small1,small2;
    /* map to scaled hexagon values */
    h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
    h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
    h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
    h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
    h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
    h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
    h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
    /* sum values and also discover the 3 largest and 3 smallest */
    big0 = small0 = h0;
    small1 = small2 = MAXINT;
    big1 = big2 = 0;
    CHECK(h1);
    CHECK(h2);
    CHECK(h3);
    CHECK(h4);
    CHECK(h5);
    CHECK(h6);
    /* Compute mean of middle 1-3 values */
    return  UNSCALE(h0 -big0 -big1 -small0 -small1 
                    -ALFRAC[(big2 + small2)>>SCALEB]);
}
#undef CHECK

static int 
atfilt4(int *p) {
/* Edge enhancement */
/* notice we use the global omaxval */
/* 'p' is 9 pixel values from 3x3 neighbors */

    int hav;
    /* map to scaled hexagon values and compute enhance value */
    hav = M0[p[0]] + M1[p[3]] + M2[p[7]];
    hav += H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
    hav += V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
    hav += V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
    hav += H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
    hav += V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
    hav += V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
    if (hav < 0)
        hav = 0;
    hav = UNSCALE(hav);
    if (hav > omaxval)
        hav = omaxval;
    return hav;
}

static int 
atfilt5(int *p) {
/* Optimal estimation - do smoothing in inverse proportion */
/* to the local variance. */
/* notice we use the globals noisevariance and omaxval*/
/* 'p' is 9 pixel values from 3x3 neighbors */

    int mean,variance,temp;
    int h0,h1,h2,h3,h4,h5,h6;       /* hexagon values    2 3   */
                                    /*                  1 0 4  */
                                    /*                   6 5   */
    /* map to scaled hexagon values */
    h0 = M0[p[0]] + M1[p[3]] + M2[p[7]];
    h1 = H0[p[0]] + H1[p[2]] + H2[p[1]] + H3[p[8]];
    h2 = V0[p[0]] + V1[p[3]] + V2[p[2]] + V3[p[1]];
    h3 = V0[p[0]] + V1[p[3]] + V2[p[4]] + V3[p[5]];
    h4 = H0[p[0]] + H1[p[4]] + H2[p[5]] + H3[p[6]];
    h5 = V0[p[0]] + V1[p[7]] + V2[p[6]] + V3[p[5]];
    h6 = V0[p[0]] + V1[p[7]] + V2[p[8]] + V3[p[1]];
    mean = h0 + h1 + h2 + h3 + h4 + h5 + h6;
    mean = AVEDIV[SCTOCSC(mean)];   /* compute scaled mean by dividing by 7 */
    temp = (h1 - mean); variance = SQUARE[NOCSVAL + SCTOCSC(temp)];  
        /* compute scaled variance */
    temp = (h2 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)]; 
        /* and rescale to keep */
    temp = (h3 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)]; 
        /* within 32 bit limits */
    temp = (h4 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)];
    temp = (h5 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)];
    temp = (h6 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)];
    temp = (h0 - mean); variance += SQUARE[NOCSVAL + SCTOCSC(temp)];   
    /* (temp = h0 - mean) */
    if (variance != 0)      /* avoid possible divide by 0 */
        temp = mean + (variance * temp) / (variance + noisevariance);   
            /* optimal estimate */
    else temp = h0;
    if (temp < 0)
        temp = 0;
    temp = RUNSCALE(temp);
    if (temp > omaxval)
        temp = omaxval;
    return temp;
}



static void 
do_one_frame(FILE *ifp) {

    pnm_writepnminit( stdout, cols, rows, omaxval, oformat, 0 );
    
    if ( PNM_FORMAT_TYPE(oformat) == PPM_TYPE ) {
        int pr[9],pg[9],pb[9];          /* 3x3 neighbor pixel values */
        int r,g,b;

        for ( row = 0; row < rows; row++ ) {
            int po,no;           /* offsets for left and right colums in 3x3 */
            xel *ip0, *ip1, *ip2, *op;

            if (row == 0) {
                irow0 = irow1;
                pnm_readpnmrow( ifp, irow1, cols, maxval, format );
            }
            if (row == (rows-1))
                irow2 = irow1;
            else
                pnm_readpnmrow( ifp, irow2, cols, maxval, format );

            for (col = cols-1,po= col>0?1:0,no=0,
                     ip0=irow0,ip1=irow1,ip2=irow2,op=orow;
                 col >= 0;
                 col--,ip0++,ip1++,ip2++,op++, no |= 1,po = col!= 0 ? po : 0) {
                                /* grab 3x3 pixel values */
                pr[0] = PPM_GETR( *ip1 );
                pg[0] = PPM_GETG( *ip1 );
                pb[0] = PPM_GETB( *ip1 );
                pr[1] = PPM_GETR( *(ip1-no) );
                pg[1] = PPM_GETG( *(ip1-no) );
                pb[1] = PPM_GETB( *(ip1-no) );
                pr[5] = PPM_GETR( *(ip1+po) );
                pg[5] = PPM_GETG( *(ip1+po) );
                pb[5] = PPM_GETB( *(ip1+po) );
                pr[3] = PPM_GETR( *(ip2) );
                pg[3] = PPM_GETG( *(ip2) );
                pb[3] = PPM_GETB( *(ip2) );
                pr[2] = PPM_GETR( *(ip2-no) );
                pg[2] = PPM_GETG( *(ip2-no) );
                pb[2] = PPM_GETB( *(ip2-no) );
                pr[4] = PPM_GETR( *(ip2+po) );
                pg[4] = PPM_GETG( *(ip2+po) );
                pb[4] = PPM_GETB( *(ip2+po) );
                pr[6] = PPM_GETR( *(ip0+po) );
                pg[6] = PPM_GETG( *(ip0+po) );
                pb[6] = PPM_GETB( *(ip0+po) );
                pr[8] = PPM_GETR( *(ip0-no) );
                pg[8] = PPM_GETG( *(ip0-no) );
                pb[8] = PPM_GETB( *(ip0-no) );
                pr[7] = PPM_GETR( *(ip0) );
                pg[7] = PPM_GETG( *(ip0) );
                pb[7] = PPM_GETB( *(ip0) );
                r = (*atfunc)(pr);
                g = (*atfunc)(pg);
                b = (*atfunc)(pb);
                PPM_ASSIGN( *op, r, g, b );
            }
            pnm_writepnmrow( stdout, orow, cols, omaxval, oformat, 0 );
            if (irow1 == irows[2]) {
                irow1 = irows[0];
                irow2 = irows[1];
                irow0 = irows[2];
            } else if (irow1 == irows[1]) {
                irow2 = irows[0];
                irow0 = irows[1];
                irow1 = irows[2];
            }
            else    /* must be at irows[0] */
            {
                irow0 = irows[0];
                irow1 = irows[1];
                irow2 = irows[2];
            }
        }
    } else {
        /* Else must be PGM */
        int p[9];               /* 3x3 neighbor pixel values */
        int pv;
        int promote;

        /* we scale maxval to omaxval */
        promote = ( PNM_FORMAT_TYPE(format) != PNM_FORMAT_TYPE(oformat) );

        for ( row = 0; row < rows; row++ ) {
            int po,no;          /* offsets for left and right colums in 3x3 */
            xel *ip0, *ip1, *ip2, *op;

            if (row == 0) {
                irow0 = irow1;
                pnm_readpnmrow( ifp, irow1, cols, maxval, format );
                if ( promote )
                    pnm_promoteformatrow( irow1, cols, maxval, 
                                          format, maxval, oformat );
            }
            if (row == (rows-1))
                irow2 = irow1;
            else {
                pnm_readpnmrow( ifp, irow2, cols, maxval, format );
                if ( promote )
                    pnm_promoteformatrow( irow2, cols, maxval, 
                                          format, maxval, oformat );
            }

            for (col = cols-1,po= col>0?1:0,no=0,
                     ip0=irow0,ip1=irow1,ip2=irow2,op=orow;
                 col >= 0;
                 col--,ip0++,ip1++,ip2++,op++, no |= 1,po = col!= 0 ? po : 0) {
                /* grab 3x3 pixel values */
                p[0] = PNM_GET1( *ip1 );
                p[1] = PNM_GET1( *(ip1-no) );
                p[5] = PNM_GET1( *(ip1+po) );
                p[3] = PNM_GET1( *(ip2) );
                p[2] = PNM_GET1( *(ip2-no) );
                p[4] = PNM_GET1( *(ip2+po) );
                p[6] = PNM_GET1( *(ip0+po) );
                p[8] = PNM_GET1( *(ip0-no) );
                p[7] = PNM_GET1( *(ip0) );
                pv = (*atfunc)(p);
                PNM_ASSIGN1( *op, pv );
            }
            pnm_writepnmrow( stdout, orow, cols, omaxval, oformat, 0 );
            if (irow1 == irows[2]) {
                irow1 = irows[0];
                irow2 = irows[1];
                irow0 = irows[2];
            } else if (irow1 == irows[1]) {
                irow2 = irows[0];
                irow0 = irows[1];
                irow1 = irows[2];
            } else {
                /* must be at irows[0] */
                irow0 = irows[0];
                irow1 = irows[1];
                irow2 = irows[2];
            }
        }
    }
}



static void
verifySame(unsigned int const imageSeq, 
           int const imageCols, int const imageRows,
           xelval const imageMaxval, int const imageFormat,
           int const cols, int const rows,
           xelval const maxval, int const format) {
/*----------------------------------------------------------------------------
   Issue error message and exit the program if the imageXXX arguments don't
   match the XXX arguments.
-----------------------------------------------------------------------------*/
    if (imageCols != cols)
        pm_error("Width of Image %u (%d) is not the same as Image 0 (%d)",
                 imageSeq, imageCols, cols);
    if (imageRows != rows)
        pm_error("Height of Image %u (%d) is not the same as Image 0 (%d)",
                 imageSeq, imageRows, rows);
    if (imageMaxval != maxval)
        pm_error("Maxval of Image %u (%u) is not the same as Image 0 (%u)",
                 imageSeq, imageMaxval, maxval);
    if (imageFormat != format)
        pm_error("Format of Image %u is not the same as Image 0",
                 imageSeq);
}



int (*atfuncs[6]) (int *) = {atfilt0,atfilt1,atfilt2,atfilt3,atfilt4,atfilt5};




int
main(int argc, char *argv[]) {

    FILE * ifp;
	bool eof;  /* We've hit the end of the input stream */
    unsigned int imageSeq;  /* Sequence number of image, starting from 0 */

    const char* const usage = "alpha radius pnmfile\n"
        "0.0 <= alpha <= 0.5 for alpha trimmed mean -or- \n"
        "1.0 <= alpha <= 2.0 for optimal estimation -or- \n"
        "-0.1 >= alpha >= -0.9 for edge enhancement\n"
        "0.3333 <= radius <= 1.0 specify effective radius\n";

    pnm_init( &argc, argv );

    if ( argc < 3 || argc > 4 )
        pm_usage( usage );

    if ( sscanf( argv[1], "%lf", &alpha ) != 1 )
        pm_usage( usage );
    if ( sscanf( argv[2], "%lf", &radius ) != 1 )
        pm_usage( usage );
        
    if ((alpha > -0.1 && alpha < 0.0) || (alpha > 0.5 && alpha < 1.0))
        pm_error( "Alpha must be in range 0.0 <= alpha <= 0.5 "
                  "for alpha trimmed mean" );
    if (alpha > 2.0)
        pm_error( "Alpha must be in range 1.0 <= alpha <= 2.0 "
                  "for optimal estimation" );
    if (alpha < -0.9 || (alpha > -0.1 && alpha < 0.0))
        pm_error( "Alpha must be in range -0.9 <= alpha <= -0.1 "
                  "for edge enhancement" );
    if (radius < 0.333 || radius > 1.0)
        pm_error( "Radius must be in range 0.333333333 <= radius <= 1.0" );

    if ( argc == 4 )
        ifp = pm_openr( argv[3] );
    else
        ifp = stdin;
        
    pnm_readpnminit( ifp, &cols, &rows, &maxval, &format );
        
    if (maxval > MXIVAL) 
        pm_error("The maxval of the input image (%d) is too large.\n"
                 "This program's limit is %d.", 
                 maxval, MXIVAL);
        
    oformat = PNM_FORMAT_TYPE(format);
    /* force output to max precision without forcing new 2-byte format */
    omaxval = MIN(maxval, PPM_MAXMAXVAL);
        
    atfunc = atfuncs[atfilt_setup(alpha, radius,
                                  (double)omaxval/(double)maxval)];

    if ( oformat < PGM_TYPE ) {
        oformat = RPGM_FORMAT;
        pm_message( "promoting file to PGM" );
    }

    orow = pnm_allocrow(cols);
    irows[0] = pnm_allocrow(cols);
    irows[1] = pnm_allocrow(cols);
    irows[2] = pnm_allocrow(cols);
    irow0 = irows[0];
    irow1 = irows[1];
    irow2 = irows[2];

    eof = FALSE;  /* We're already in the middle of the first image */
    imageSeq = 0;
    while (!eof) {
        do_one_frame(ifp);
        pm_nextimage(ifp, &eof);
        if (!eof) {
            /* Read and validate header of next image */
            int imageCols, imageRows;
            xelval imageMaxval;
            int imageFormat;

            ++imageSeq;
            pnm_readpnminit(ifp, &imageCols, &imageRows, 
                            &imageMaxval, &imageFormat);
            verifySame(imageSeq,
                       imageCols, imageRows, imageMaxval, imageFormat,
                       cols, rows, maxval, format);
        }
    }

    pnm_freerow(irow0);
    pnm_freerow(irow1);
    pnm_freerow(irow2);
    pnm_freerow(orow);
    pm_close(ifp);

    return 0;
}