summaryrefslogtreecommitdiffhomepage
path: root/libpng/contrib/gregbook/rpng2-win.c
blob: fbdacb59bc4b6c91837f9cbd353325ed16c03c62 (plain)
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
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
/*---------------------------------------------------------------------------

   rpng2 - progressive-model PNG display program                rpng2-win.c

   This program decodes and displays PNG files progressively, as if it were
   a web browser (though the front end is only set up to read from files).
   It supports gamma correction, user-specified background colors, and user-
   specified background patterns (for transparent images).  This version is
   for 32-bit Windows; it may compile under 16-bit Windows with a little
   tweaking (or maybe not).  Thanks to Adam Costello and Pieter S. van der
   Meulen for the "diamond" and "radial waves" patterns, respectively.

   to do (someday, maybe):
    - handle quoted command-line args (especially filenames with spaces)
    - finish resizable checkerboard-gradient (sizes 4-128?)
    - use %.1023s to simplify truncation of title-bar string?
    - have minimum window width:  oh well

  ---------------------------------------------------------------------------

   Changelog:
    - 1.01:  initial public release
    - 1.02:  fixed cut-and-paste error in usage screen (oops...)
    - 1.03:  modified to allow abbreviated options
    - 1.04:  removed bogus extra argument from usage fprintf() [Glenn R-P?];
              fixed command-line parsing bug
    - 1.10:  enabled "message window"/console (thanks to David Geldreich)
    - 1.20:  added runtime MMX-enabling/disabling and new -mmx* options
    - 1.21:  made minor tweak to usage screen to fit within 25-line console
    - 1.22:  added AMD64/EM64T support (__x86_64__)
    - 2.00:  dual-licensed (added GNU GPL)
    - 2.01:  fixed 64-bit typo in readpng2.c
    - 2.02:  fixed improper display of usage screen on PNG error(s); fixed
              unexpected-EOF and file-read-error cases
    - 2.03:  removed runtime MMX-enabling/disabling and obsolete -mmx* options

  ---------------------------------------------------------------------------

      Copyright (c) 1998-2008 Greg Roelofs.  All rights reserved.

      This software is provided "as is," without warranty of any kind,
      express or implied.  In no event shall the author or contributors
      be held liable for any damages arising in any way from the use of
      this software.

      The contents of this file are DUAL-LICENSED.  You may modify and/or
      redistribute this software according to the terms of one of the
      following two licenses (at your option):


      LICENSE 1 ("BSD-like with advertising clause"):

      Permission is granted to anyone to use this software for any purpose,
      including commercial applications, and to alter it and redistribute
      it freely, subject to the following restrictions:

      1. Redistributions of source code must retain the above copyright
         notice, disclaimer, and this list of conditions.
      2. Redistributions in binary form must reproduce the above copyright
         notice, disclaimer, and this list of conditions in the documenta-
         tion and/or other materials provided with the distribution.
      3. All advertising materials mentioning features or use of this
         software must display the following acknowledgment:

            This product includes software developed by Greg Roelofs
            and contributors for the book, "PNG: The Definitive Guide,"
            published by O'Reilly and Associates.


      LICENSE 2 (GNU GPL v2 or later):

      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.

      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software Foundation,
      Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

  ---------------------------------------------------------------------------*/

#define PROGNAME  "rpng2-win"
#define LONGNAME  "Progressive PNG Viewer for Windows"
#define VERSION   "2.02 of 16 March 2008"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <setjmp.h>    /* for jmpbuf declaration in readpng2.h */
#include <time.h>
#include <math.h>      /* only for PvdM background code */
#include <windows.h>
#ifdef __CYGWIN__
/* getch replacement. Turns out, we don't really need this,
 * but leave it here if we ever enable any of the uses of
 * _getch in the main code
 */
#include <unistd.h>
#include <termio.h>
#include <sys/ioctl.h>
int repl_getch( void )
{
  char ch;
  int fd = fileno(stdin);
  struct termio old_tty, new_tty;

  ioctl(fd, TCGETA, &old_tty);
  new_tty = old_tty;
  new_tty.c_lflag &= ~(ICANON | ECHO | ISIG);
  ioctl(fd, TCSETA, &new_tty);
  fread(&ch, 1, sizeof(ch), stdin);
  ioctl(fd, TCSETA, &old_tty);

  return ch;
}
#define _getch repl_getch
#else
#include <conio.h>     /* only for _getch() */
#endif

/* all for PvdM background code: */
#ifndef PI
#  define PI             3.141592653589793238
#endif
#define PI_2             (PI*0.5)
#define INV_PI_360       (360.0 / PI)
#define MAX(a,b)         (a>b?a:b)
#define MIN(a,b)         (a<b?a:b)
#define CLIP(a,min,max)  MAX(min,MIN((a),max))
#define ABS(a)           ((a)<0?-(a):(a))
#define CLIP8P(c)        MAX(0,(MIN((c),255)))   /* 8-bit pos. integer (uch) */
#define ROUNDF(f)        ((int)(f + 0.5))

#define rgb1_max   bg_freq
#define rgb1_min   bg_gray
#define rgb2_max   bg_bsat
#define rgb2_min   bg_brot

/* #define DEBUG */     /* this enables the Trace() macros */

#include "readpng2.h"   /* typedefs, common macros, readpng2 prototypes */


/* could just include png.h, but this macro is the only thing we need
 * (name and typedefs changed to local versions); note that side effects
 * only happen with alpha (which could easily be avoided with
 * "ush acopy = (alpha);") */

#define alpha_composite(composite, fg, alpha, bg) {               \
    ush temp = ((ush)(fg)*(ush)(alpha) +                          \
                (ush)(bg)*(ush)(255 - (ush)(alpha)) + (ush)128);  \
    (composite) = (uch)((temp + (temp >> 8)) >> 8);               \
}


#define INBUFSIZE 4096   /* with pseudo-timing on (1 sec delay/block), this
                          *  block size corresponds roughly to a download
                          *  speed 10% faster than theoretical 33.6K maximum
                          *  (assuming 8 data bits, 1 stop bit and no other
                          *  overhead) */

/* local prototypes */
static void       rpng2_win_init(void);
static int        rpng2_win_create_window(void);
static int        rpng2_win_load_bg_image(void);
static void       rpng2_win_display_row(ulg row);
static void       rpng2_win_finish_display(void);
static void       rpng2_win_cleanup(void);
LRESULT CALLBACK  rpng2_win_wndproc(HWND, UINT, WPARAM, LPARAM);


static char titlebar[1024];
static char *progname = PROGNAME;
static char *appname = LONGNAME;
static char *filename;
static FILE *infile;

static mainprog_info rpng2_info;

static uch inbuf[INBUFSIZE];
static int incount;

static int pat = 6;         /* must be less than num_bgpat */
static int bg_image = 0;
static int bgscale = 16;
static ulg bg_rowbytes;
static uch *bg_data;

static struct rgb_color {
    uch r, g, b;
} rgb[] = {
    {  0,   0,   0},    /*  0:  black */
    {255, 255, 255},    /*  1:  white */
    {173, 132,  57},    /*  2:  tan */
    { 64, 132,   0},    /*  3:  medium green */
    {189, 117,   1},    /*  4:  gold */
    {253, 249,   1},    /*  5:  yellow */
    {  0,   0, 255},    /*  6:  blue */
    {  0,   0, 120},    /*  7:  medium blue */
    {255,   0, 255},    /*  8:  magenta */
    { 64,   0,  64},    /*  9:  dark magenta */
    {255,   0,   0},    /* 10:  red */
    { 64,   0,   0},    /* 11:  dark red */
    {255, 127,   0},    /* 12:  orange */
    {192,  96,   0},    /* 13:  darker orange */
    { 24,  60,   0},    /* 14:  dark green-yellow */
    { 85, 125, 200}     /* 15:  ice blue */
};
/* not used for now, but should be for error-checking:
static int num_rgb = sizeof(rgb) / sizeof(struct rgb_color);
 */

/*
    This whole struct is a fairly cheesy way to keep the number of
    command-line options to a minimum.  The radial-waves background
    type is a particularly poor fit to the integer elements of the
    struct...but a few macros and a little fixed-point math will do
    wonders for ya.

    type bits:
       F E D C B A 9 8 7 6 5 4 3 2 1 0
                             | | | | |
                             | | +-+-+-- 0 = sharp-edged checkerboard
                             | |         1 = soft diamonds
                             | |         2 = radial waves
                             | |       3-7 = undefined
                             | +-- gradient #2 inverted?
                             +-- alternating columns inverted?
 */
static struct background_pattern {
    ush type;
    int rgb1_max, rgb1_min;     /* or bg_freq, bg_gray */
    int rgb2_max, rgb2_min;     /* or bg_bsat, bg_brot (both scaled by 10)*/
} bg[] = {
    {0+8,   2,0,  1,15},        /* checkered:  tan/black vs. white/ice blue */
    {0+24,  2,0,  1,0},         /* checkered:  tan/black vs. white/black */
    {0+8,   4,5,  0,2},         /* checkered:  gold/yellow vs. black/tan */
    {0+8,   4,5,  0,6},         /* checkered:  gold/yellow vs. black/blue */
    {0,     7,0,  8,9},         /* checkered:  deep blue/black vs. magenta */
    {0+8,  13,0,  5,14},        /* checkered:  orange/black vs. yellow */
    {0+8,  12,0, 10,11},        /* checkered:  orange/black vs. red */
    {1,     7,0,  8,0},         /* diamonds:  deep blue/black vs. magenta */
    {1,    12,0, 11,0},         /* diamonds:  orange vs. dark red */
    {1,    10,0,  7,0},         /* diamonds:  red vs. medium blue */
    {1,     4,0,  5,0},         /* diamonds:  gold vs. yellow */
    {1,     3,0,  0,0},         /* diamonds:  medium green vs. black */
    {2,    16, 100,  20,   0},  /* radial:  ~hard radial color-beams */
    {2,    18, 100,  10,   2},  /* radial:  soft, curved radial color-beams */
    {2,    16, 256, 100, 250},  /* radial:  very tight spiral */
    {2, 10000, 256,  11,   0}   /* radial:  dipole-moire' (almost fractal) */
};
static int num_bgpat = sizeof(bg) / sizeof(struct background_pattern);


/* Windows-specific global variables (could go in struct, but messy...) */
static ulg wimage_rowbytes;
static uch *dib;
static uch *wimage_data;
static BITMAPINFOHEADER *bmih;

static HWND global_hwnd;
static HINSTANCE global_hInst;
static int global_showmode;




int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInst, PSTR cmd, int showmode)
{
    char *args[1024];                 /* arbitrary limit, but should suffice */
    char **argv = args;
    char *p, *q, *bgstr = NULL;
    int argc = 0;
    int rc, alen, flen;
    int error = 0;
    int timing = FALSE;
    int have_bg = FALSE;
    double LUT_exponent;              /* just the lookup table */
    double CRT_exponent = 2.2;        /* just the monitor */
    double default_display_exponent;  /* whole display system */
    MSG msg;


    /* First initialize a few things, just to be sure--memset takes care of
     * default background color (black), booleans (FALSE), pointers (NULL),
     * etc. */

    global_hInst = hInst;
    global_showmode = showmode;
    filename = (char *)NULL;
    memset(&rpng2_info, 0, sizeof(mainprog_info));

#ifndef __CYGWIN__
    /* Next reenable console output, which normally goes to the bit bucket
     * for windowed apps.  Closing the console window will terminate the
     * app.  Thanks to David.Geldreich@realviz.com for supplying the magical
     * incantation. */

    AllocConsole();
    freopen("CONOUT$", "a", stderr);
    freopen("CONOUT$", "a", stdout);
#endif

    /* Set the default value for our display-system exponent, i.e., the
     * product of the CRT exponent and the exponent corresponding to
     * the frame-buffer's lookup table (LUT), if any.  This is not an
     * exhaustive list of LUT values (e.g., OpenStep has a lot of weird
     * ones), but it should cover 99% of the current possibilities.  And
     * yes, these ifdefs are completely wasted in a Windows program... */

#if defined(NeXT)
    /* third-party utilities can modify the default LUT exponent */
    LUT_exponent = 1.0 / 2.2;
    /*
    if (some_next_function_that_returns_gamma(&next_gamma))
        LUT_exponent = 1.0 / next_gamma;
     */
#elif defined(sgi)
    LUT_exponent = 1.0 / 1.7;
    /* there doesn't seem to be any documented function to
     * get the "gamma" value, so we do it the hard way */
    infile = fopen("/etc/config/system.glGammaVal", "r");
    if (infile) {
        double sgi_gamma;

        fgets(tmpline, 80, infile);
        fclose(infile);
        sgi_gamma = atof(tmpline);
        if (sgi_gamma > 0.0)
            LUT_exponent = 1.0 / sgi_gamma;
    }
#elif defined(Macintosh)
    LUT_exponent = 1.8 / 2.61;
    /*
    if (some_mac_function_that_returns_gamma(&mac_gamma))
        LUT_exponent = mac_gamma / 2.61;
     */
#else
    LUT_exponent = 1.0;   /* assume no LUT:  most PCs */
#endif

    /* the defaults above give 1.0, 1.3, 1.5 and 2.2, respectively: */
    default_display_exponent = LUT_exponent * CRT_exponent;


    /* If the user has set the SCREEN_GAMMA environment variable as suggested
     * (somewhat imprecisely) in the libpng documentation, use that; otherwise
     * use the default value we just calculated.  Either way, the user may
     * override this via a command-line option. */

    if ((p = getenv("SCREEN_GAMMA")) != NULL)
        rpng2_info.display_exponent = atof(p);
    else
        rpng2_info.display_exponent = default_display_exponent;


    /* Windows really hates command lines, so we have to set up our own argv.
     * Note that we do NOT bother with quoted arguments here, so don't use
     * filenames with spaces in 'em! */

    argv[argc++] = PROGNAME;
    p = cmd;
    for (;;) {
        if (*p == ' ')
            while (*++p == ' ')
                ;
        /* now p points at the first non-space after some spaces */
        if (*p == '\0')
            break;    /* nothing after the spaces:  done */
        argv[argc++] = q = p;
        while (*q && *q != ' ')
            ++q;
        /* now q points at a space or the end of the string */
        if (*q == '\0')
            break;    /* last argv already terminated; quit */
        *q = '\0';    /* change space to terminator */
        p = q + 1;
    }
    argv[argc] = NULL;   /* terminate the argv array itself */


    /* Now parse the command line for options and the PNG filename. */

    while (*++argv && !error) {
        if (!strncmp(*argv, "-gamma", 2)) {
            if (!*++argv)
                ++error;
            else {
                rpng2_info.display_exponent = atof(*argv);
                if (rpng2_info.display_exponent <= 0.0)
                    ++error;
            }
        } else if (!strncmp(*argv, "-bgcolor", 4)) {
            if (!*++argv)
                ++error;
            else {
                bgstr = *argv;
                if (strlen(bgstr) != 7 || bgstr[0] != '#')
                    ++error;
                else {
                    have_bg = TRUE;
                    bg_image = FALSE;
                }
            }
        } else if (!strncmp(*argv, "-bgpat", 4)) {
            if (!*++argv)
                ++error;
            else {
                pat = atoi(*argv) - 1;
                if (pat < 0 || pat >= num_bgpat)
                    ++error;
                else {
                    bg_image = TRUE;
                    have_bg = FALSE;
                }
            }
        } else if (!strncmp(*argv, "-timing", 2)) {
            timing = TRUE;
        } else {
            if (**argv != '-') {
                filename = *argv;
                if (argv[1])   /* shouldn't be any more args after filename */
                    ++error;
            } else
                ++error;   /* not expecting any other options */
        }
    }

    if (!filename)
        ++error;


    /* print usage screen if any errors up to this point */

    if (error) {
#ifndef __CYGWIN__
        int ch;
#endif

        fprintf(stderr, "\n%s %s:  %s\n\n", PROGNAME, VERSION, appname);
        readpng2_version_info();
        fprintf(stderr, "\n"
          "Usage:  %s [-gamma exp] [-bgcolor bg | -bgpat pat] [-timing]\n"
          "        %*s file.png\n\n"
          "    exp \ttransfer-function exponent (``gamma'') of the display\n"
          "\t\t  system in floating-point format (e.g., ``%.1f''); equal\n"
          "\t\t  to the product of the lookup-table exponent (varies)\n"
          "\t\t  and the CRT exponent (usually 2.2); must be positive\n"
          "    bg  \tdesired background color in 7-character hex RGB format\n"
          "\t\t  (e.g., ``#ff7700'' for orange:  same as HTML colors);\n"
          "\t\t  used with transparent images; overrides -bgpat option\n"
          "    pat \tdesired background pattern number (1-%d); used with\n"
          "\t\t  transparent images; overrides -bgcolor option\n"
          "    -timing\tenables delay for every block read, to simulate modem\n"
          "\t\t  download of image (~36 Kbps)\n"
          "\nPress Q, Esc or mouse button 1 after image is displayed to quit.\n"
#ifndef __CYGWIN__
          "Press Q or Esc to quit this usage screen. ",
#else
          ,
#endif
          PROGNAME,
#if (defined(__i386__) || defined(_M_IX86) || defined(__x86_64__)) && \
    !(defined(__CYGWIN__) || defined(__MINGW32__))
          (int)strlen(PROGNAME), " ",
#endif
          (int)strlen(PROGNAME), " ", default_display_exponent, num_bgpat);
        fflush(stderr);
#ifndef __CYGWIN__
        do
            ch = _getch();
        while (ch != 'q' && ch != 'Q' && ch != 0x1B);
#endif
        exit(1);
    }


    if (!(infile = fopen(filename, "rb"))) {
        fprintf(stderr, PROGNAME ":  can't open PNG file [%s]\n", filename);
        ++error;
    } else {
        incount = fread(inbuf, 1, INBUFSIZE, infile);
        if (incount < 8 || !readpng2_check_sig(inbuf, 8)) {
            fprintf(stderr, PROGNAME
              ":  [%s] is not a PNG file: incorrect signature\n",
              filename);
            ++error;
        } else if ((rc = readpng2_init(&rpng2_info)) != 0) {
            switch (rc) {
                case 2:
                    fprintf(stderr, PROGNAME
                      ":  [%s] has bad IHDR (libpng longjmp)\n", filename);
                    break;
                case 4:
                    fprintf(stderr, PROGNAME ":  insufficient memory\n");
                    break;
                default:
                    fprintf(stderr, PROGNAME
                      ":  unknown readpng2_init() error\n");
                    break;
            }
            ++error;
        }
        if (error)
            fclose(infile);
    }


    if (error) {
#ifndef __CYGWIN__
        int ch;
#endif

        fprintf(stderr, PROGNAME ":  aborting.\n");
#ifndef __CYGWIN__
        do
            ch = _getch();
        while (ch != 'q' && ch != 'Q' && ch != 0x1B);
#endif
        exit(2);
    } else {
        fprintf(stderr, "\n%s %s:  %s\n", PROGNAME, VERSION, appname);
#ifndef __CYGWIN__
        fprintf(stderr,
          "\n   [console window:  closing this window will terminate %s]\n\n",
          PROGNAME);
#endif
        fflush(stderr);
    }


    /* set the title-bar string, but make sure buffer doesn't overflow */

    alen = strlen(appname);
    flen = strlen(filename);
    if (alen + flen + 3 > 1023)
        sprintf(titlebar, "%s:  ...%s", appname, filename+(alen+flen+6-1023));
    else
        sprintf(titlebar, "%s:  %s", appname, filename);


    /* set some final rpng2_info variables before entering main data loop */

    if (have_bg) {
        unsigned r, g, b;   /* this approach quiets compiler warnings */

        sscanf(bgstr+1, "%2x%2x%2x", &r, &g, &b);
        rpng2_info.bg_red   = (uch)r;
        rpng2_info.bg_green = (uch)g;
        rpng2_info.bg_blue  = (uch)b;
    } else
        rpng2_info.need_bgcolor = TRUE;

    rpng2_info.state = kPreInit;
    rpng2_info.mainprog_init = rpng2_win_init;
    rpng2_info.mainprog_display_row = rpng2_win_display_row;
    rpng2_info.mainprog_finish_display = rpng2_win_finish_display;


    /* OK, this is the fun part:  call readpng2_decode_data() at the start of
     * the loop to deal with our first buffer of data (read in above to verify
     * that the file is a PNG image), then loop through the file and continue
     * calling the same routine to handle each chunk of data.  It in turn
     * passes the data to libpng, which will invoke one or more of our call-
     * backs as decoded data become available.  We optionally call Sleep() for
     * one second per iteration to simulate downloading the image via an analog
     * modem. */

    for (;;) {
        Trace((stderr, "about to call readpng2_decode_data()\n"))
        if (readpng2_decode_data(&rpng2_info, inbuf, incount))
            ++error;
        Trace((stderr, "done with readpng2_decode_data()\n"))

        if (error || incount != INBUFSIZE || rpng2_info.state == kDone) {
            if (rpng2_info.state == kDone) {
                Trace((stderr, "done decoding PNG image\n"))
            } else if (ferror(infile)) {
                fprintf(stderr, PROGNAME
                  ":  error while reading PNG image file\n");
                exit(3);
            } else if (feof(infile)) {
                fprintf(stderr, PROGNAME ":  end of file reached "
                  "(unexpectedly) while reading PNG image file\n");
                exit(3);
            } else /* if (error) */ {
                // will print error message below
            }
            break;
        }

        if (timing)
            Sleep(1000L);

        incount = fread(inbuf, 1, INBUFSIZE, infile);
    }


    /* clean up PNG stuff and report any decoding errors */

    fclose(infile);
    Trace((stderr, "about to call readpng2_cleanup()\n"))
    readpng2_cleanup(&rpng2_info);

    if (error) {
        fprintf(stderr, PROGNAME ":  libpng error while decoding PNG image\n");
        exit(3);
    }


    /* wait for the user to tell us when to quit */

    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }


    /* we're done:  clean up all image and Windows resources and go away */

    Trace((stderr, "about to call rpng2_win_cleanup()\n"))
    rpng2_win_cleanup();

    return msg.wParam;
}





/* this function is called by readpng2_info_callback() in readpng2.c, which
 * in turn is called by libpng after all of the pre-IDAT chunks have been
 * read and processed--i.e., we now have enough info to finish initializing */

static void rpng2_win_init()
{
    ulg i;
    ulg rowbytes = rpng2_info.rowbytes;

    Trace((stderr, "beginning rpng2_win_init()\n"))
    Trace((stderr, "  rowbytes = %d\n", rpng2_info.rowbytes))
    Trace((stderr, "  width  = %ld\n", rpng2_info.width))
    Trace((stderr, "  height = %ld\n", rpng2_info.height))

    rpng2_info.image_data = (uch *)malloc(rowbytes * rpng2_info.height);
    if (!rpng2_info.image_data) {
        readpng2_cleanup(&rpng2_info);
        return;
    }

    rpng2_info.row_pointers = (uch **)malloc(rpng2_info.height * sizeof(uch *));
    if (!rpng2_info.row_pointers) {
        free(rpng2_info.image_data);
        rpng2_info.image_data = NULL;
        readpng2_cleanup(&rpng2_info);
        return;
    }

    for (i = 0;  i < rpng2_info.height;  ++i)
        rpng2_info.row_pointers[i] = rpng2_info.image_data + i*rowbytes;

/*---------------------------------------------------------------------------
    Do the basic Windows initialization stuff, make the window, and fill it
    with the user-specified, file-specified or default background color.
  ---------------------------------------------------------------------------*/

    if (rpng2_win_create_window()) {
        readpng2_cleanup(&rpng2_info);
        return;
    }

    rpng2_info.state = kWindowInit;
}





static int rpng2_win_create_window()
{
    uch bg_red   = rpng2_info.bg_red;
    uch bg_green = rpng2_info.bg_green;
    uch bg_blue  = rpng2_info.bg_blue;
    uch *dest;
    int extra_width, extra_height;
    ulg i, j;
    WNDCLASSEX wndclass;
    RECT rect;


/*---------------------------------------------------------------------------
    Allocate memory for the display-specific version of the image (round up
    to multiple of 4 for Windows DIB).
  ---------------------------------------------------------------------------*/

    wimage_rowbytes = ((3*rpng2_info.width + 3L) >> 2) << 2;

    if (!(dib = (uch *)malloc(sizeof(BITMAPINFOHEADER) +
                              wimage_rowbytes*rpng2_info.height)))
    {
        return 4;   /* fail */
    }

/*---------------------------------------------------------------------------
    Initialize the DIB.  Negative height means to use top-down BMP ordering
    (must be uncompressed, but that's what we want).  Bit count of 1, 4 or 8
    implies a colormap of RGBX quads, but 24-bit BMPs just use B,G,R values
    directly => wimage_data begins immediately after BMP header.
  ---------------------------------------------------------------------------*/

    memset(dib, 0, sizeof(BITMAPINFOHEADER));
    bmih = (BITMAPINFOHEADER *)dib;
    bmih->biSize = sizeof(BITMAPINFOHEADER);
    bmih->biWidth = rpng2_info.width;
    bmih->biHeight = -((long)rpng2_info.height);
    bmih->biPlanes = 1;
    bmih->biBitCount = 24;
    bmih->biCompression = 0;
    wimage_data = dib + sizeof(BITMAPINFOHEADER);

/*---------------------------------------------------------------------------
    Fill window with the specified background color (default is black), but
    defer loading faked "background image" until window is displayed (may be
    slow to compute).  Data are in BGR order.
  ---------------------------------------------------------------------------*/

    if (bg_image) {   /* just fill with black for now */
        memset(wimage_data, 0, wimage_rowbytes*rpng2_info.height);
    } else {
        for (j = 0;  j < rpng2_info.height;  ++j) {
            dest = wimage_data + j*wimage_rowbytes;
            for (i = rpng2_info.width;  i > 0;  --i) {
                *dest++ = bg_blue;
                *dest++ = bg_green;
                *dest++ = bg_red;
            }
        }
    }

/*---------------------------------------------------------------------------
    Set the window parameters.
  ---------------------------------------------------------------------------*/

    memset(&wndclass, 0, sizeof(wndclass));

    wndclass.cbSize = sizeof(wndclass);
    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = rpng2_win_wndproc;
    wndclass.hInstance = global_hInst;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(DKGRAY_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = progname;
    wndclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    RegisterClassEx(&wndclass);

/*---------------------------------------------------------------------------
    Finally, create the window.
  ---------------------------------------------------------------------------*/

    extra_width  = 2*(GetSystemMetrics(SM_CXBORDER) +
                      GetSystemMetrics(SM_CXDLGFRAME));
    extra_height = 2*(GetSystemMetrics(SM_CYBORDER) +
                      GetSystemMetrics(SM_CYDLGFRAME)) +
                      GetSystemMetrics(SM_CYCAPTION);

    global_hwnd = CreateWindow(progname, titlebar, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, CW_USEDEFAULT, rpng2_info.width+extra_width,
      rpng2_info.height+extra_height, NULL, NULL, global_hInst, NULL);

    ShowWindow(global_hwnd, global_showmode);
    UpdateWindow(global_hwnd);

/*---------------------------------------------------------------------------
    Now compute the background image and display it.  If it fails (memory
    allocation), revert to a plain background color.
  ---------------------------------------------------------------------------*/

    if (bg_image) {
        static const char *msg = "Computing background image...";
        int x, y, len = strlen(msg);
        HDC hdc = GetDC(global_hwnd);
        TEXTMETRIC tm;

        GetTextMetrics(hdc, &tm);
        x = (rpng2_info.width - len*tm.tmAveCharWidth)/2;
        y = (rpng2_info.height - tm.tmHeight)/2;
        SetBkMode(hdc, TRANSPARENT);
        SetTextColor(hdc, GetSysColor(COLOR_HIGHLIGHTTEXT));
        /* this can still begin out of bounds even if x is positive (???): */
        TextOut(hdc, ((x < 0)? 0 : x), ((y < 0)? 0 : y), msg, len);
        ReleaseDC(global_hwnd, hdc);

        rpng2_win_load_bg_image();   /* resets bg_image if fails */
    }

    if (!bg_image) {
        for (j = 0;  j < rpng2_info.height;  ++j) {
            dest = wimage_data + j*wimage_rowbytes;
            for (i = rpng2_info.width;  i > 0;  --i) {
                *dest++ = bg_blue;
                *dest++ = bg_green;
                *dest++ = bg_red;
            }
        }
    }

    rect.left = 0L;
    rect.top = 0L;
    rect.right = (LONG)rpng2_info.width;       /* possibly off by one? */
    rect.bottom = (LONG)rpng2_info.height;     /* possibly off by one? */
    InvalidateRect(global_hwnd, &rect, FALSE);
    UpdateWindow(global_hwnd);                 /* similar to XFlush() */

    return 0;

} /* end function rpng2_win_create_window() */





static int rpng2_win_load_bg_image()
{
    uch *src, *dest;
    uch r1, r2, g1, g2, b1, b2;
    uch r1_inv, r2_inv, g1_inv, g2_inv, b1_inv, b2_inv;
    int k, hmax, max;
    int xidx, yidx, yidx_max = (bgscale-1);
    int even_odd_vert, even_odd_horiz, even_odd;
    int invert_gradient2 = (bg[pat].type & 0x08);
    int invert_column;
    ulg i, row;

/*---------------------------------------------------------------------------
    Allocate buffer for fake background image to be used with transparent
    images; if this fails, revert to plain background color.
  ---------------------------------------------------------------------------*/

    bg_rowbytes = 3 * rpng2_info.width;
    bg_data = (uch *)malloc(bg_rowbytes * rpng2_info.height);
    if (!bg_data) {
        fprintf(stderr, PROGNAME
          ":  unable to allocate memory for background image\n");
        bg_image = 0;
        return 1;
    }

/*---------------------------------------------------------------------------
    Vertical gradients (ramps) in NxN squares, alternating direction and
    colors (N == bgscale).
  ---------------------------------------------------------------------------*/

    if ((bg[pat].type & 0x07) == 0) {
        uch r1_min  = rgb[bg[pat].rgb1_min].r;
        uch g1_min  = rgb[bg[pat].rgb1_min].g;
        uch b1_min  = rgb[bg[pat].rgb1_min].b;
        uch r2_min  = rgb[bg[pat].rgb2_min].r;
        uch g2_min  = rgb[bg[pat].rgb2_min].g;
        uch b2_min  = rgb[bg[pat].rgb2_min].b;
        int r1_diff = rgb[bg[pat].rgb1_max].r - r1_min;
        int g1_diff = rgb[bg[pat].rgb1_max].g - g1_min;
        int b1_diff = rgb[bg[pat].rgb1_max].b - b1_min;
        int r2_diff = rgb[bg[pat].rgb2_max].r - r2_min;
        int g2_diff = rgb[bg[pat].rgb2_max].g - g2_min;
        int b2_diff = rgb[bg[pat].rgb2_max].b - b2_min;

        for (row = 0;  row < rpng2_info.height;  ++row) {
            yidx = row % bgscale;
            even_odd_vert = (row / bgscale) & 1;

            r1 = r1_min + (r1_diff * yidx) / yidx_max;
            g1 = g1_min + (g1_diff * yidx) / yidx_max;
            b1 = b1_min + (b1_diff * yidx) / yidx_max;
            r1_inv = r1_min + (r1_diff * (yidx_max-yidx)) / yidx_max;
            g1_inv = g1_min + (g1_diff * (yidx_max-yidx)) / yidx_max;
            b1_inv = b1_min + (b1_diff * (yidx_max-yidx)) / yidx_max;

            r2 = r2_min + (r2_diff * yidx) / yidx_max;
            g2 = g2_min + (g2_diff * yidx) / yidx_max;
            b2 = b2_min + (b2_diff * yidx) / yidx_max;
            r2_inv = r2_min + (r2_diff * (yidx_max-yidx)) / yidx_max;
            g2_inv = g2_min + (g2_diff * (yidx_max-yidx)) / yidx_max;
            b2_inv = b2_min + (b2_diff * (yidx_max-yidx)) / yidx_max;

            dest = bg_data + row*bg_rowbytes;
            for (i = 0;  i < rpng2_info.width;  ++i) {
                even_odd_horiz = (i / bgscale) & 1;
                even_odd = even_odd_vert ^ even_odd_horiz;
                invert_column =
                  (even_odd_horiz && (bg[pat].type & 0x10));
                if (even_odd == 0) {         /* gradient #1 */
                    if (invert_column) {
                        *dest++ = r1_inv;
                        *dest++ = g1_inv;
                        *dest++ = b1_inv;
                    } else {
                        *dest++ = r1;
                        *dest++ = g1;
                        *dest++ = b1;
                    }
                } else {                     /* gradient #2 */
                    if ((invert_column && invert_gradient2) ||
                        (!invert_column && !invert_gradient2))
                    {
                        *dest++ = r2;        /* not inverted or */
                        *dest++ = g2;        /*  doubly inverted */
                        *dest++ = b2;
                    } else {
                        *dest++ = r2_inv;
                        *dest++ = g2_inv;    /* singly inverted */
                        *dest++ = b2_inv;
                    }
                }
            }
        }

/*---------------------------------------------------------------------------
    Soft gradient-diamonds with scale = bgscale.  Code contributed by Adam
    M. Costello.
  ---------------------------------------------------------------------------*/

    } else if ((bg[pat].type & 0x07) == 1) {

        hmax = (bgscale-1)/2;   /* half the max weight of a color */
        max = 2*hmax;           /* the max weight of a color */

        r1 = rgb[bg[pat].rgb1_max].r;
        g1 = rgb[bg[pat].rgb1_max].g;
        b1 = rgb[bg[pat].rgb1_max].b;
        r2 = rgb[bg[pat].rgb2_max].r;
        g2 = rgb[bg[pat].rgb2_max].g;
        b2 = rgb[bg[pat].rgb2_max].b;

        for (row = 0;  row < rpng2_info.height;  ++row) {
            yidx = row % bgscale;
            if (yidx > hmax)
                yidx = bgscale-1 - yidx;
            dest = bg_data + row*bg_rowbytes;
            for (i = 0;  i < rpng2_info.width;  ++i) {
                xidx = i % bgscale;
                if (xidx > hmax)
                    xidx = bgscale-1 - xidx;
                k = xidx + yidx;
                *dest++ = (k*r1 + (max-k)*r2) / max;
                *dest++ = (k*g1 + (max-k)*g2) / max;
                *dest++ = (k*b1 + (max-k)*b2) / max;
            }
        }

/*---------------------------------------------------------------------------
    Radial "starburst" with azimuthal sinusoids; [eventually number of sinu-
    soids will equal bgscale?].  This one is slow but very cool.  Code con-
    tributed by Pieter S. van der Meulen (originally in Smalltalk).
  ---------------------------------------------------------------------------*/

    } else if ((bg[pat].type & 0x07) == 2) {
        uch ch;
        int ii, x, y, hw, hh, grayspot;
        double freq, rotate, saturate, gray, intensity;
        double angle=0.0, aoffset=0.0, maxDist, dist;
        double red=0.0, green=0.0, blue=0.0, hue, s, v, f, p, q, t;

        fprintf(stderr, "%s:  computing radial background...",
          PROGNAME);
        fflush(stderr);

        hh = rpng2_info.height / 2;
        hw = rpng2_info.width / 2;

        /* variables for radial waves:
         *   aoffset:  number of degrees to rotate hue [CURRENTLY NOT USED]
         *   freq:  number of color beams originating from the center
         *   grayspot:  size of the graying center area (anti-alias)
         *   rotate:  rotation of the beams as a function of radius
         *   saturate:  saturation of beams' shape azimuthally
         */
        angle = CLIP(angle, 0.0, 360.0);
        grayspot = CLIP(bg[pat].bg_gray, 1, (hh + hw));
        freq = MAX((double)bg[pat].bg_freq, 0.0);
        saturate = (double)bg[pat].bg_bsat * 0.1;
        rotate = (double)bg[pat].bg_brot * 0.1;
        gray = 0.0;
        intensity = 0.0;
        maxDist = (double)((hw*hw) + (hh*hh));

        for (row = 0;  row < rpng2_info.height;  ++row) {
            y = row - hh;
            dest = bg_data + row*bg_rowbytes;
            for (i = 0;  i < rpng2_info.width;  ++i) {
                x = i - hw;
                angle = (x == 0)? PI_2 : atan((double)y / (double)x);
                gray = (double)MAX(ABS(y), ABS(x)) / grayspot;
                gray = MIN(1.0, gray);
                dist = (double)((x*x) + (y*y)) / maxDist;
                intensity = cos((angle+(rotate*dist*PI)) * freq) *
                  gray * saturate;
                intensity = (MAX(MIN(intensity,1.0),-1.0) + 1.0) * 0.5;
                hue = (angle + PI) * INV_PI_360 + aoffset;
                s = gray * ((double)(ABS(x)+ABS(y)) / (double)(hw + hh));
                s = MIN(MAX(s,0.0), 1.0);
                v = MIN(MAX(intensity,0.0), 1.0);

                if (s == 0.0) {
                    ch = (uch)(v * 255.0);
                    *dest++ = ch;
                    *dest++ = ch;
                    *dest++ = ch;
                } else {
                    if ((hue < 0.0) || (hue >= 360.0))
                        hue -= (((int)(hue / 360.0)) * 360.0);
                    hue /= 60.0;
                    ii = (int)hue;
                    f = hue - (double)ii;
                    p = (1.0 - s) * v;
                    q = (1.0 - (s * f)) * v;
                    t = (1.0 - (s * (1.0 - f))) * v;
                    if      (ii == 0) { red = v; green = t; blue = p; }
                    else if (ii == 1) { red = q; green = v; blue = p; }
                    else if (ii == 2) { red = p; green = v; blue = t; }
                    else if (ii == 3) { red = p; green = q; blue = v; }
                    else if (ii == 4) { red = t; green = p; blue = v; }
                    else if (ii == 5) { red = v; green = p; blue = q; }
                    *dest++ = (uch)(red * 255.0);
                    *dest++ = (uch)(green * 255.0);
                    *dest++ = (uch)(blue * 255.0);
                }
            }
        }
        fprintf(stderr, "done.\n");
        fflush(stderr);
    }

/*---------------------------------------------------------------------------
    Blast background image to display buffer before beginning PNG decode;
    calling function will handle invalidation and UpdateWindow() call.
  ---------------------------------------------------------------------------*/

    for (row = 0;  row < rpng2_info.height;  ++row) {
        src = bg_data + row*bg_rowbytes;
        dest = wimage_data + row*wimage_rowbytes;
        for (i = rpng2_info.width;  i > 0;  --i) {
            r1 = *src++;
            g1 = *src++;
            b1 = *src++;
            *dest++ = b1;
            *dest++ = g1;   /* note reverse order */
            *dest++ = r1;
        }
    }

    return 0;

} /* end function rpng2_win_load_bg_image() */





static void rpng2_win_display_row(ulg row)
{
    uch bg_red   = rpng2_info.bg_red;
    uch bg_green = rpng2_info.bg_green;
    uch bg_blue  = rpng2_info.bg_blue;
    uch *src, *src2=NULL, *dest;
    uch r, g, b, a;
    ulg i;
    static int rows=0;
    static ulg firstrow;

/*---------------------------------------------------------------------------
    rows and firstrow simply track how many rows (and which ones) have not
    yet been displayed; alternatively, we could call InvalidateRect() for
    every row and not bother with the records-keeping.
  ---------------------------------------------------------------------------*/

    Trace((stderr, "beginning rpng2_win_display_row()\n"))

    if (rows == 0)
        firstrow = row;   /* first row not yet displayed */

    ++rows;   /* count of rows received but not yet displayed */

/*---------------------------------------------------------------------------
    Aside from the use of the rpng2_info struct and the lack of an outer
    loop (over rows), this routine is identical to rpng_win_display_image()
    in the non-progressive version of the program.
  ---------------------------------------------------------------------------*/

    src = rpng2_info.image_data + row*rpng2_info.rowbytes;
    if (bg_image)
        src2 = bg_data + row*bg_rowbytes;
    dest = wimage_data + row*wimage_rowbytes;

    if (rpng2_info.channels == 3) {
        for (i = rpng2_info.width;  i > 0;  --i) {
            r = *src++;
            g = *src++;
            b = *src++;
            *dest++ = b;
            *dest++ = g;   /* note reverse order */
            *dest++ = r;
        }
    } else /* if (rpng2_info.channels == 4) */ {
        for (i = rpng2_info.width;  i > 0;  --i) {
            r = *src++;
            g = *src++;
            b = *src++;
            a = *src++;
            if (bg_image) {
                bg_red   = *src2++;
                bg_green = *src2++;
                bg_blue  = *src2++;
            }
            if (a == 255) {
                *dest++ = b;
                *dest++ = g;
                *dest++ = r;
            } else if (a == 0) {
                *dest++ = bg_blue;
                *dest++ = bg_green;
                *dest++ = bg_red;
            } else {
                /* this macro (copied from png.h) composites the
                 * foreground and background values and puts the
                 * result into the first argument; there are no
                 * side effects with the first argument */
                alpha_composite(*dest++, b, a, bg_blue);
                alpha_composite(*dest++, g, a, bg_green);
                alpha_composite(*dest++, r, a, bg_red);
            }
        }
    }

/*---------------------------------------------------------------------------
    Display after every 16 rows or when on last row.  (Region may include
    previously displayed lines due to interlacing--i.e., not contiguous.)
  ---------------------------------------------------------------------------*/

    if ((rows & 0xf) == 0 || row == rpng2_info.height-1) {
        RECT rect;

        rect.left = 0L;
        rect.top = (LONG)firstrow;
        rect.right = (LONG)rpng2_info.width;       /* possibly off by one? */
        rect.bottom = (LONG)row + 1L;              /* possibly off by one? */
        InvalidateRect(global_hwnd, &rect, FALSE);
        UpdateWindow(global_hwnd);                 /* similar to XFlush() */
        rows = 0;
    }

} /* end function rpng2_win_display_row() */





static void rpng2_win_finish_display()
{
    Trace((stderr, "beginning rpng2_win_finish_display()\n"))

    /* last row has already been displayed by rpng2_win_display_row(), so
     * we have nothing to do here except set a flag and let the user know
     * that the image is done */

    rpng2_info.state = kDone;
    printf(
#ifndef __CYGWIN__
      "Done.  Press Q, Esc or mouse button 1 (within image window) to quit.\n"
#else
      "Done.  Press mouse button 1 (within image window) to quit.\n"
#endif
    );
    fflush(stdout);
}





static void rpng2_win_cleanup()
{
    if (bg_image && bg_data) {
        free(bg_data);
        bg_data = NULL;
    }

    if (rpng2_info.image_data) {
        free(rpng2_info.image_data);
        rpng2_info.image_data = NULL;
    }

    if (rpng2_info.row_pointers) {
        free(rpng2_info.row_pointers);
        rpng2_info.row_pointers = NULL;
    }

    if (dib) {
        free(dib);
        dib = NULL;
    }
}





LRESULT CALLBACK rpng2_win_wndproc(HWND hwnd, UINT iMsg, WPARAM wP, LPARAM lP)
{
    HDC         hdc;
    PAINTSTRUCT ps;
    int rc;

    switch (iMsg) {
        case WM_CREATE:
            /* one-time processing here, if any */
            return 0;

        case WM_PAINT:
            hdc = BeginPaint(hwnd, &ps);
            rc = StretchDIBits(hdc, 0, 0, rpng2_info.width, rpng2_info.height,
                                    0, 0, rpng2_info.width, rpng2_info.height,
                                    wimage_data, (BITMAPINFO *)bmih,
                                    0, SRCCOPY);
            EndPaint(hwnd, &ps);
            return 0;

        /* wait for the user to tell us when to quit */
        case WM_CHAR:
            switch (wP) {       /* only need one, so ignore repeat count */
                case 'q':
                case 'Q':
                case 0x1B:      /* Esc key */
                    PostQuitMessage(0);
            }
            return 0;

        case WM_LBUTTONDOWN:    /* another way of quitting */
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
    }

    return DefWindowProc(hwnd, iMsg, wP, lP);
}