summaryrefslogtreecommitdiff
path: root/plugingui/png/pngread.c
blob: 1d8c6b33469be48503a8daaf579264a2e6fa3146 (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
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305

/* pngread.c - read a PNG file
 *
 * Last changed in libpng 1.5.10 [March 8, 2012]
 * Copyright (c) 1998-2012 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 *
 * This file contains routines that an application calls directly to
 * read a PNG file or stream.
 */

#include "pngpriv.h"

#ifdef PNG_READ_SUPPORTED

/* Create a PNG structure for reading, and allocate any memory needed. */
PNG_FUNCTION(png_structp,PNGAPI
png_create_read_struct,(png_const_charp user_png_ver, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warn_fn),PNG_ALLOCATED)
{

#ifdef PNG_USER_MEM_SUPPORTED
   return (png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
       warn_fn, NULL, NULL, NULL));
}

/* Alternate create PNG structure for reading, and allocate any memory
 * needed.
 */
PNG_FUNCTION(png_structp,PNGAPI
png_create_read_struct_2,(png_const_charp user_png_ver, png_voidp error_ptr,
    png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
    png_malloc_ptr malloc_fn, png_free_ptr free_fn),PNG_ALLOCATED)
{
#endif /* PNG_USER_MEM_SUPPORTED */

#ifdef PNG_SETJMP_SUPPORTED
   volatile
#endif
   png_structp png_ptr;
   volatile int png_cleanup_needed = 0;

#ifdef PNG_SETJMP_SUPPORTED
#ifdef USE_FAR_KEYWORD
   jmp_buf tmp_jmpbuf;
#endif
#endif

   png_debug(1, "in png_create_read_struct");

#ifdef PNG_USER_MEM_SUPPORTED
   png_ptr = (png_structp)png_create_struct_2(PNG_STRUCT_PNG,
       malloc_fn, mem_ptr);
#else
   png_ptr = (png_structp)png_create_struct(PNG_STRUCT_PNG);
#endif
   if (png_ptr == NULL)
      return (NULL);

   /* Added at libpng-1.2.6 */
#ifdef PNG_USER_LIMITS_SUPPORTED
   png_ptr->user_width_max = PNG_USER_WIDTH_MAX;
   png_ptr->user_height_max = PNG_USER_HEIGHT_MAX;

   /* Added at libpng-1.2.43 and 1.4.0 */
   png_ptr->user_chunk_cache_max = PNG_USER_CHUNK_CACHE_MAX;

   /* Added at libpng-1.2.43 and 1.4.1 */
   png_ptr->user_chunk_malloc_max = PNG_USER_CHUNK_MALLOC_MAX;
#endif

#ifdef PNG_SETJMP_SUPPORTED
/* Applications that neglect to set up their own setjmp() and then
 * encounter a png_error() will longjmp here.  Since the jmpbuf is
 * then meaningless we abort instead of returning.
 */
#ifdef USE_FAR_KEYWORD
   if (setjmp(tmp_jmpbuf))
#else
   if (setjmp(png_jmpbuf(png_ptr))) /* Sets longjmp to match setjmp */
#endif
      PNG_ABORT();
#ifdef USE_FAR_KEYWORD
   png_memcpy(png_jmpbuf(png_ptr), tmp_jmpbuf, png_sizeof(jmp_buf));
#endif
#endif /* PNG_SETJMP_SUPPORTED */

#ifdef PNG_USER_MEM_SUPPORTED
   png_set_mem_fn(png_ptr, mem_ptr, malloc_fn, free_fn);
#endif

   png_set_error_fn(png_ptr, error_ptr, error_fn, warn_fn);

   /* Call the general version checker (shared with read and write code): */
   if (!png_user_version_check(png_ptr, user_png_ver))
      png_cleanup_needed = 1;

   if (!png_cleanup_needed)
   {
   /* Initialize zbuf - compression buffer */
   png_ptr->zbuf_size = PNG_ZBUF_SIZE;
   png_ptr->zbuf = (png_bytep)png_malloc_warn(png_ptr, png_ptr->zbuf_size);

   if (png_ptr->zbuf == NULL)
      png_cleanup_needed = 1;
   }

   png_ptr->zstream.zalloc = png_zalloc;
   png_ptr->zstream.zfree = png_zfree;
   png_ptr->zstream.opaque = (voidpf)png_ptr;

   if (!png_cleanup_needed)
   {
      switch (inflateInit(&png_ptr->zstream))
      {
         case Z_OK:
            break; /* Do nothing */

         case Z_MEM_ERROR:
            png_warning(png_ptr, "zlib memory error");
            png_cleanup_needed = 1;
            break;

         case Z_STREAM_ERROR:
            png_warning(png_ptr, "zlib stream error");
            png_cleanup_needed = 1;
            break;

         case Z_VERSION_ERROR:
            png_warning(png_ptr, "zlib version error");
            png_cleanup_needed = 1;
            break;

         default: png_warning(png_ptr, "Unknown zlib error");
            png_cleanup_needed = 1;
      }
   }

   if (png_cleanup_needed)
   {
      /* Clean up PNG structure and deallocate any memory. */
      png_free(png_ptr, png_ptr->zbuf);
      png_ptr->zbuf = NULL;
#ifdef PNG_USER_MEM_SUPPORTED
      png_destroy_struct_2((png_voidp)png_ptr,
          (png_free_ptr)free_fn, (png_voidp)mem_ptr);
#else
      png_destroy_struct((png_voidp)png_ptr);
#endif
      return (NULL);
   }

   png_ptr->zstream.next_out = png_ptr->zbuf;
   png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;

   png_set_read_fn(png_ptr, NULL, NULL);


   return (png_ptr);
}


#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Read the information before the actual image data.  This has been
 * changed in v0.90 to allow reading a file that already has the magic
 * bytes read from the stream.  You can tell libpng how many bytes have
 * been read from the beginning of the stream (up to the maximum of 8)
 * via png_set_sig_bytes(), and we will only check the remaining bytes
 * here.  The application can then have access to the signature bytes we
 * read if it is determined that this isn't a valid PNG file.
 */
void PNGAPI
png_read_info(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_read_info");

   if (png_ptr == NULL || info_ptr == NULL)
      return;

   /* Read and check the PNG file signature. */
   png_read_sig(png_ptr, info_ptr);

   for (;;)
   {
      png_uint_32 length = png_read_chunk_header(png_ptr);
      png_uint_32 chunk_name = png_ptr->chunk_name;

      /* This should be a binary subdivision search or a hash for
       * matching the chunk name rather than a linear search.
       */
      if (chunk_name == png_IDAT)
         if (png_ptr->mode & PNG_AFTER_IDAT)
            png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;

      if (chunk_name == png_IHDR)
         png_handle_IHDR(png_ptr, info_ptr, length);

      else if (chunk_name == png_IEND)
         png_handle_IEND(png_ptr, info_ptr, length);

#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
      else if (png_chunk_unknown_handling(png_ptr, chunk_name) !=
         PNG_HANDLE_CHUNK_AS_DEFAULT)
      {
         if (chunk_name == png_IDAT)
            png_ptr->mode |= PNG_HAVE_IDAT;

         png_handle_unknown(png_ptr, info_ptr, length);

         if (chunk_name == png_PLTE)
            png_ptr->mode |= PNG_HAVE_PLTE;

         else if (chunk_name == png_IDAT)
         {
            if (!(png_ptr->mode & PNG_HAVE_IHDR))
               png_error(png_ptr, "Missing IHDR before IDAT");

            else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
                !(png_ptr->mode & PNG_HAVE_PLTE))
               png_error(png_ptr, "Missing PLTE before IDAT");

            break;
         }
      }
#endif
      else if (chunk_name == png_PLTE)
         png_handle_PLTE(png_ptr, info_ptr, length);

      else if (chunk_name == png_IDAT)
      {
         if (!(png_ptr->mode & PNG_HAVE_IHDR))
            png_error(png_ptr, "Missing IHDR before IDAT");

         else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
             !(png_ptr->mode & PNG_HAVE_PLTE))
            png_error(png_ptr, "Missing PLTE before IDAT");

         png_ptr->idat_size = length;
         png_ptr->mode |= PNG_HAVE_IDAT;
         break;
      }

#ifdef PNG_READ_bKGD_SUPPORTED
      else if (chunk_name == png_bKGD)
         png_handle_bKGD(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_cHRM_SUPPORTED
      else if (chunk_name == png_cHRM)
         png_handle_cHRM(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_gAMA_SUPPORTED
      else if (chunk_name == png_gAMA)
         png_handle_gAMA(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_hIST_SUPPORTED
      else if (chunk_name == png_hIST)
         png_handle_hIST(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_oFFs_SUPPORTED
      else if (chunk_name == png_oFFs)
         png_handle_oFFs(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_pCAL_SUPPORTED
      else if (chunk_name == png_pCAL)
         png_handle_pCAL(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sCAL_SUPPORTED
      else if (chunk_name == png_sCAL)
         png_handle_sCAL(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_pHYs_SUPPORTED
      else if (chunk_name == png_pHYs)
         png_handle_pHYs(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sBIT_SUPPORTED
      else if (chunk_name == png_sBIT)
         png_handle_sBIT(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sRGB_SUPPORTED
      else if (chunk_name == png_sRGB)
         png_handle_sRGB(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_iCCP_SUPPORTED
      else if (chunk_name == png_iCCP)
         png_handle_iCCP(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sPLT_SUPPORTED
      else if (chunk_name == png_sPLT)
         png_handle_sPLT(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_tEXt_SUPPORTED
      else if (chunk_name == png_tEXt)
         png_handle_tEXt(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_tIME_SUPPORTED
      else if (chunk_name == png_tIME)
         png_handle_tIME(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_tRNS_SUPPORTED
      else if (chunk_name == png_tRNS)
         png_handle_tRNS(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_zTXt_SUPPORTED
      else if (chunk_name == png_zTXt)
         png_handle_zTXt(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_iTXt_SUPPORTED
      else if (chunk_name == png_iTXt)
         png_handle_iTXt(png_ptr, info_ptr, length);
#endif

      else
         png_handle_unknown(png_ptr, info_ptr, length);
   }
}
#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

/* Optional call to update the users info_ptr structure */
void PNGAPI
png_read_update_info(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_read_update_info");

   if (png_ptr == NULL)
      return;

   png_read_start_row(png_ptr);

#ifdef PNG_READ_TRANSFORMS_SUPPORTED
   png_read_transform_info(png_ptr, info_ptr);
#else
   PNG_UNUSED(info_ptr)
#endif
}

#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Initialize palette, background, etc, after transformations
 * are set, but before any reading takes place.  This allows
 * the user to obtain a gamma-corrected palette, for example.
 * If the user doesn't call this, we will do it ourselves.
 */
void PNGAPI
png_start_read_image(png_structp png_ptr)
{
   png_debug(1, "in png_start_read_image");

   if (png_ptr != NULL)
     png_read_start_row(png_ptr);
}
#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
void PNGAPI
png_read_row(png_structp png_ptr, png_bytep row, png_bytep dsp_row)
{
   int ret;

   png_row_info row_info;

   if (png_ptr == NULL)
      return;

   png_debug2(1, "in png_read_row (row %lu, pass %d)",
       (unsigned long)png_ptr->row_number, png_ptr->pass);

   /* png_read_start_row sets the information (in particular iwidth) for this
    * interlace pass.
    */
   if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
      png_read_start_row(png_ptr);

   /* 1.5.6: row_info moved out of png_struct to a local here. */
   row_info.width = png_ptr->iwidth; /* NOTE: width of current interlaced row */
   row_info.color_type = png_ptr->color_type;
   row_info.bit_depth = png_ptr->bit_depth;
   row_info.channels = png_ptr->channels;
   row_info.pixel_depth = png_ptr->pixel_depth;
   row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);

   if (png_ptr->row_number == 0 && png_ptr->pass == 0)
   {
   /* Check for transforms that have been set but were defined out */
#if defined(PNG_WRITE_INVERT_SUPPORTED) && !defined(PNG_READ_INVERT_SUPPORTED)
   if (png_ptr->transformations & PNG_INVERT_MONO)
      png_warning(png_ptr, "PNG_READ_INVERT_SUPPORTED is not defined");
#endif

#if defined(PNG_WRITE_FILLER_SUPPORTED) && !defined(PNG_READ_FILLER_SUPPORTED)
   if (png_ptr->transformations & PNG_FILLER)
      png_warning(png_ptr, "PNG_READ_FILLER_SUPPORTED is not defined");
#endif

#if defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
    !defined(PNG_READ_PACKSWAP_SUPPORTED)
   if (png_ptr->transformations & PNG_PACKSWAP)
      png_warning(png_ptr, "PNG_READ_PACKSWAP_SUPPORTED is not defined");
#endif

#if defined(PNG_WRITE_PACK_SUPPORTED) && !defined(PNG_READ_PACK_SUPPORTED)
   if (png_ptr->transformations & PNG_PACK)
      png_warning(png_ptr, "PNG_READ_PACK_SUPPORTED is not defined");
#endif

#if defined(PNG_WRITE_SHIFT_SUPPORTED) && !defined(PNG_READ_SHIFT_SUPPORTED)
   if (png_ptr->transformations & PNG_SHIFT)
      png_warning(png_ptr, "PNG_READ_SHIFT_SUPPORTED is not defined");
#endif

#if defined(PNG_WRITE_BGR_SUPPORTED) && !defined(PNG_READ_BGR_SUPPORTED)
   if (png_ptr->transformations & PNG_BGR)
      png_warning(png_ptr, "PNG_READ_BGR_SUPPORTED is not defined");
#endif

#if defined(PNG_WRITE_SWAP_SUPPORTED) && !defined(PNG_READ_SWAP_SUPPORTED)
   if (png_ptr->transformations & PNG_SWAP_BYTES)
      png_warning(png_ptr, "PNG_READ_SWAP_SUPPORTED is not defined");
#endif
   }

#ifdef PNG_READ_INTERLACING_SUPPORTED
   /* If interlaced and we do not need a new row, combine row and return.
    * Notice that the pixels we have from previous rows have been transformed
    * already; we can only combine like with like (transformed or
    * untransformed) and, because of the libpng API for interlaced images, this
    * means we must transform before de-interlacing.
    */
   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
   {
      switch (png_ptr->pass)
      {
         case 0:
            if (png_ptr->row_number & 0x07)
            {
               if (dsp_row != NULL)
                  png_combine_row(png_ptr, dsp_row, 1/*display*/);
               png_read_finish_row(png_ptr);
               return;
            }
            break;

         case 1:
            if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
            {
               if (dsp_row != NULL)
                  png_combine_row(png_ptr, dsp_row, 1/*display*/);

               png_read_finish_row(png_ptr);
               return;
            }
            break;

         case 2:
            if ((png_ptr->row_number & 0x07) != 4)
            {
               if (dsp_row != NULL && (png_ptr->row_number & 4))
                  png_combine_row(png_ptr, dsp_row, 1/*display*/);

               png_read_finish_row(png_ptr);
               return;
            }
            break;

         case 3:
            if ((png_ptr->row_number & 3) || png_ptr->width < 3)
            {
               if (dsp_row != NULL)
                  png_combine_row(png_ptr, dsp_row, 1/*display*/);

               png_read_finish_row(png_ptr);
               return;
            }
            break;

         case 4:
            if ((png_ptr->row_number & 3) != 2)
            {
               if (dsp_row != NULL && (png_ptr->row_number & 2))
                  png_combine_row(png_ptr, dsp_row, 1/*display*/);

               png_read_finish_row(png_ptr);
               return;
            }
            break;
         case 5:
            if ((png_ptr->row_number & 1) || png_ptr->width < 2)
            {
               if (dsp_row != NULL)
                  png_combine_row(png_ptr, dsp_row, 1/*display*/);

               png_read_finish_row(png_ptr);
               return;
            }
            break;

         default:
         case 6:
            if (!(png_ptr->row_number & 1))
            {
               png_read_finish_row(png_ptr);
               return;
            }
            break;
      }
   }
#endif

   if (!(png_ptr->mode & PNG_HAVE_IDAT))
      png_error(png_ptr, "Invalid attempt to read row data");

   png_ptr->zstream.next_out = png_ptr->row_buf;
   png_ptr->zstream.avail_out =
       (uInt)(PNG_ROWBYTES(png_ptr->pixel_depth,
       png_ptr->iwidth) + 1);

   do
   {
      if (!(png_ptr->zstream.avail_in))
      {
         while (!png_ptr->idat_size)
         {
            png_crc_finish(png_ptr, 0);

            png_ptr->idat_size = png_read_chunk_header(png_ptr);
            if (png_ptr->chunk_name != png_IDAT)
               png_error(png_ptr, "Not enough image data");
         }
         png_ptr->zstream.avail_in = (uInt)png_ptr->zbuf_size;
         png_ptr->zstream.next_in = png_ptr->zbuf;
         if (png_ptr->zbuf_size > png_ptr->idat_size)
            png_ptr->zstream.avail_in = (uInt)png_ptr->idat_size;
         png_crc_read(png_ptr, png_ptr->zbuf,
             (png_size_t)png_ptr->zstream.avail_in);
         png_ptr->idat_size -= png_ptr->zstream.avail_in;
      }

      ret = inflate(&png_ptr->zstream, Z_PARTIAL_FLUSH);

      if (ret == Z_STREAM_END)
      {
         if (png_ptr->zstream.avail_out || png_ptr->zstream.avail_in ||
            png_ptr->idat_size)
            png_benign_error(png_ptr, "Extra compressed data");
         png_ptr->mode |= PNG_AFTER_IDAT;
         png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
         break;
      }

      if (ret != Z_OK)
         png_error(png_ptr, png_ptr->zstream.msg ? png_ptr->zstream.msg :
             "Decompression error");

   } while (png_ptr->zstream.avail_out);

   if (png_ptr->row_buf[0] > PNG_FILTER_VALUE_NONE)
   {
      if (png_ptr->row_buf[0] < PNG_FILTER_VALUE_LAST)
         png_read_filter_row(png_ptr, &row_info, png_ptr->row_buf + 1,
            png_ptr->prev_row + 1, png_ptr->row_buf[0]);
      else
         png_error(png_ptr, "bad adaptive filter value");
   }

   /* libpng 1.5.6: the following line was copying png_ptr->rowbytes before
    * 1.5.6, while the buffer really is this big in current versions of libpng
    * it may not be in the future, so this was changed just to copy the
    * interlaced count:
    */
   png_memcpy(png_ptr->prev_row, png_ptr->row_buf, row_info.rowbytes + 1);

#ifdef PNG_MNG_FEATURES_SUPPORTED
   if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
       (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
   {
      /* Intrapixel differencing */
      png_do_read_intrapixel(&row_info, png_ptr->row_buf + 1);
   }
#endif


#ifdef PNG_READ_TRANSFORMS_SUPPORTED
   if (png_ptr->transformations)
      png_do_read_transformations(png_ptr, &row_info);
#endif

   /* The transformed pixel depth should match the depth now in row_info. */
   if (png_ptr->transformed_pixel_depth == 0)
   {
      png_ptr->transformed_pixel_depth = row_info.pixel_depth;
      if (row_info.pixel_depth > png_ptr->maximum_pixel_depth)
         png_error(png_ptr, "sequential row overflow");
   }

   else if (png_ptr->transformed_pixel_depth != row_info.pixel_depth)
      png_error(png_ptr, "internal sequential row size calculation error");

#ifdef PNG_READ_INTERLACING_SUPPORTED
   /* Blow up interlaced rows to full size */
   if (png_ptr->interlaced &&
      (png_ptr->transformations & PNG_INTERLACE))
   {
      if (png_ptr->pass < 6)
         png_do_read_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass,
            png_ptr->transformations);

      if (dsp_row != NULL)
         png_combine_row(png_ptr, dsp_row, 1/*display*/);

      if (row != NULL)
         png_combine_row(png_ptr, row, 0/*row*/);
   }

   else
#endif
   {
      if (row != NULL)
         png_combine_row(png_ptr, row, -1/*ignored*/);

      if (dsp_row != NULL)
         png_combine_row(png_ptr, dsp_row, -1/*ignored*/);
   }
   png_read_finish_row(png_ptr);

   if (png_ptr->read_row_fn != NULL)
      (*(png_ptr->read_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
}
#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Read one or more rows of image data.  If the image is interlaced,
 * and png_set_interlace_handling() has been called, the rows need to
 * contain the contents of the rows from the previous pass.  If the
 * image has alpha or transparency, and png_handle_alpha()[*] has been
 * called, the rows contents must be initialized to the contents of the
 * screen.
 *
 * "row" holds the actual image, and pixels are placed in it
 * as they arrive.  If the image is displayed after each pass, it will
 * appear to "sparkle" in.  "display_row" can be used to display a
 * "chunky" progressive image, with finer detail added as it becomes
 * available.  If you do not want this "chunky" display, you may pass
 * NULL for display_row.  If you do not want the sparkle display, and
 * you have not called png_handle_alpha(), you may pass NULL for rows.
 * If you have called png_handle_alpha(), and the image has either an
 * alpha channel or a transparency chunk, you must provide a buffer for
 * rows.  In this case, you do not have to provide a display_row buffer
 * also, but you may.  If the image is not interlaced, or if you have
 * not called png_set_interlace_handling(), the display_row buffer will
 * be ignored, so pass NULL to it.
 *
 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
 */

void PNGAPI
png_read_rows(png_structp png_ptr, png_bytepp row,
    png_bytepp display_row, png_uint_32 num_rows)
{
   png_uint_32 i;
   png_bytepp rp;
   png_bytepp dp;

   png_debug(1, "in png_read_rows");

   if (png_ptr == NULL)
      return;

   rp = row;
   dp = display_row;
   if (rp != NULL && dp != NULL)
      for (i = 0; i < num_rows; i++)
      {
         png_bytep rptr = *rp++;
         png_bytep dptr = *dp++;

         png_read_row(png_ptr, rptr, dptr);
      }

   else if (rp != NULL)
      for (i = 0; i < num_rows; i++)
      {
         png_bytep rptr = *rp;
         png_read_row(png_ptr, rptr, NULL);
         rp++;
      }

   else if (dp != NULL)
      for (i = 0; i < num_rows; i++)
      {
         png_bytep dptr = *dp;
         png_read_row(png_ptr, NULL, dptr);
         dp++;
      }
}
#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Read the entire image.  If the image has an alpha channel or a tRNS
 * chunk, and you have called png_handle_alpha()[*], you will need to
 * initialize the image to the current image that PNG will be overlaying.
 * We set the num_rows again here, in case it was incorrectly set in
 * png_read_start_row() by a call to png_read_update_info() or
 * png_start_read_image() if png_set_interlace_handling() wasn't called
 * prior to either of these functions like it should have been.  You can
 * only call this function once.  If you desire to have an image for
 * each pass of a interlaced image, use png_read_rows() instead.
 *
 * [*] png_handle_alpha() does not exist yet, as of this version of libpng
 */
void PNGAPI
png_read_image(png_structp png_ptr, png_bytepp image)
{
   png_uint_32 i, image_height;
   int pass, j;
   png_bytepp rp;

   png_debug(1, "in png_read_image");

   if (png_ptr == NULL)
      return;

#ifdef PNG_READ_INTERLACING_SUPPORTED
   if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
   {
      pass = png_set_interlace_handling(png_ptr);
      /* And make sure transforms are initialized. */
      png_start_read_image(png_ptr);
   }
   else
   {
      if (png_ptr->interlaced && !(png_ptr->transformations & PNG_INTERLACE))
      {
         /* Caller called png_start_read_image or png_read_update_info without
          * first turning on the PNG_INTERLACE transform.  We can fix this here,
          * but the caller should do it!
          */
         png_warning(png_ptr, "Interlace handling should be turned on when "
            "using png_read_image");
         /* Make sure this is set correctly */
         png_ptr->num_rows = png_ptr->height;
      }

      /* Obtain the pass number, which also turns on the PNG_INTERLACE flag in
       * the above error case.
       */
      pass = png_set_interlace_handling(png_ptr);
   }
#else
   if (png_ptr->interlaced)
      png_error(png_ptr,
          "Cannot read interlaced image -- interlace handler disabled");

   pass = 1;
#endif

   image_height=png_ptr->height;

   for (j = 0; j < pass; j++)
   {
      rp = image;
      for (i = 0; i < image_height; i++)
      {
         png_read_row(png_ptr, *rp, NULL);
         rp++;
      }
   }
}
#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
/* Read the end of the PNG file.  Will not read past the end of the
 * file, will verify the end is accurate, and will read any comments
 * or time information at the end of the file, if info is not NULL.
 */
void PNGAPI
png_read_end(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_read_end");

   if (png_ptr == NULL)
      return;

   png_crc_finish(png_ptr, 0); /* Finish off CRC from last IDAT chunk */

#ifdef PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED
   /* Report invalid palette index; added at libng-1.5.10 */
   if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
      png_ptr->num_palette_max > png_ptr->num_palette)
     png_benign_error(png_ptr, "Read palette index exceeding num_palette");
#endif

   do
   {
      png_uint_32 length = png_read_chunk_header(png_ptr);
      png_uint_32 chunk_name = png_ptr->chunk_name;

      if (chunk_name == png_IHDR)
         png_handle_IHDR(png_ptr, info_ptr, length);

      else if (chunk_name == png_IEND)
         png_handle_IEND(png_ptr, info_ptr, length);

#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
      else if (png_chunk_unknown_handling(png_ptr, chunk_name) !=
         PNG_HANDLE_CHUNK_AS_DEFAULT)
      {
         if (chunk_name == png_IDAT)
         {
            if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
               png_benign_error(png_ptr, "Too many IDATs found");
         }
         png_handle_unknown(png_ptr, info_ptr, length);
         if (chunk_name == png_PLTE)
            png_ptr->mode |= PNG_HAVE_PLTE;
      }
#endif

      else if (chunk_name == png_IDAT)
      {
         /* Zero length IDATs are legal after the last IDAT has been
          * read, but not after other chunks have been read.
          */
         if ((length > 0) || (png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
            png_benign_error(png_ptr, "Too many IDATs found");

         png_crc_finish(png_ptr, length);
      }
      else if (chunk_name == png_PLTE)
         png_handle_PLTE(png_ptr, info_ptr, length);

#ifdef PNG_READ_bKGD_SUPPORTED
      else if (chunk_name == png_bKGD)
         png_handle_bKGD(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_cHRM_SUPPORTED
      else if (chunk_name == png_cHRM)
         png_handle_cHRM(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_gAMA_SUPPORTED
      else if (chunk_name == png_gAMA)
         png_handle_gAMA(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_hIST_SUPPORTED
      else if (chunk_name == png_hIST)
         png_handle_hIST(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_oFFs_SUPPORTED
      else if (chunk_name == png_oFFs)
         png_handle_oFFs(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_pCAL_SUPPORTED
      else if (chunk_name == png_pCAL)
         png_handle_pCAL(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sCAL_SUPPORTED
      else if (chunk_name == png_sCAL)
         png_handle_sCAL(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_pHYs_SUPPORTED
      else if (chunk_name == png_pHYs)
         png_handle_pHYs(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sBIT_SUPPORTED
      else if (chunk_name == png_sBIT)
         png_handle_sBIT(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sRGB_SUPPORTED
      else if (chunk_name == png_sRGB)
         png_handle_sRGB(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_iCCP_SUPPORTED
      else if (chunk_name == png_iCCP)
         png_handle_iCCP(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_sPLT_SUPPORTED
      else if (chunk_name == png_sPLT)
         png_handle_sPLT(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_tEXt_SUPPORTED
      else if (chunk_name == png_tEXt)
         png_handle_tEXt(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_tIME_SUPPORTED
      else if (chunk_name == png_tIME)
         png_handle_tIME(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_tRNS_SUPPORTED
      else if (chunk_name == png_tRNS)
         png_handle_tRNS(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_zTXt_SUPPORTED
      else if (chunk_name == png_zTXt)
         png_handle_zTXt(png_ptr, info_ptr, length);
#endif

#ifdef PNG_READ_iTXt_SUPPORTED
      else if (chunk_name == png_iTXt)
         png_handle_iTXt(png_ptr, info_ptr, length);
#endif

      else
         png_handle_unknown(png_ptr, info_ptr, length);
   } while (!(png_ptr->mode & PNG_HAVE_IEND));
}
#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */

/* Free all memory used by the read */
void PNGAPI
png_destroy_read_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr,
    png_infopp end_info_ptr_ptr)
{
   png_structp png_ptr = NULL;
   png_infop info_ptr = NULL, end_info_ptr = NULL;
#ifdef PNG_USER_MEM_SUPPORTED
   png_free_ptr free_fn = NULL;
   png_voidp mem_ptr = NULL;
#endif

   png_debug(1, "in png_destroy_read_struct");

   if (png_ptr_ptr != NULL)
      png_ptr = *png_ptr_ptr;
   if (png_ptr == NULL)
      return;

#ifdef PNG_USER_MEM_SUPPORTED
   free_fn = png_ptr->free_fn;
   mem_ptr = png_ptr->mem_ptr;
#endif

   if (info_ptr_ptr != NULL)
      info_ptr = *info_ptr_ptr;

   if (end_info_ptr_ptr != NULL)
      end_info_ptr = *end_info_ptr_ptr;

   png_read_destroy(png_ptr, info_ptr, end_info_ptr);

   if (info_ptr != NULL)
   {
#ifdef PNG_TEXT_SUPPORTED
      png_free_data(png_ptr, info_ptr, PNG_FREE_TEXT, -1);
#endif

#ifdef PNG_USER_MEM_SUPPORTED
      png_destroy_struct_2((png_voidp)info_ptr, (png_free_ptr)free_fn,
          (png_voidp)mem_ptr);
#else
      png_destroy_struct((png_voidp)info_ptr);
#endif
      *info_ptr_ptr = NULL;
   }

   if (end_info_ptr != NULL)
   {
#ifdef PNG_READ_TEXT_SUPPORTED
      png_free_data(png_ptr, end_info_ptr, PNG_FREE_TEXT, -1);
#endif
#ifdef PNG_USER_MEM_SUPPORTED
      png_destroy_struct_2((png_voidp)end_info_ptr, (png_free_ptr)free_fn,
          (png_voidp)mem_ptr);
#else
      png_destroy_struct((png_voidp)end_info_ptr);
#endif
      *end_info_ptr_ptr = NULL;
   }

   if (png_ptr != NULL)
   {
#ifdef PNG_USER_MEM_SUPPORTED
      png_destroy_struct_2((png_voidp)png_ptr, (png_free_ptr)free_fn,
          (png_voidp)mem_ptr);
#else
      png_destroy_struct((png_voidp)png_ptr);
#endif
      *png_ptr_ptr = NULL;
   }
}

/* Free all memory used by the read (old method) */
void /* PRIVATE */
png_read_destroy(png_structp png_ptr, png_infop info_ptr,
    png_infop end_info_ptr)
{
#ifdef PNG_SETJMP_SUPPORTED
   jmp_buf tmp_jmp;
#endif
   png_error_ptr error_fn;
#ifdef PNG_WARNINGS_SUPPORTED
   png_error_ptr warning_fn;
#endif
   png_voidp error_ptr;
#ifdef PNG_USER_MEM_SUPPORTED
   png_free_ptr free_fn;
#endif

   png_debug(1, "in png_read_destroy");

   if (info_ptr != NULL)
      png_info_destroy(png_ptr, info_ptr);

   if (end_info_ptr != NULL)
      png_info_destroy(png_ptr, end_info_ptr);

#ifdef PNG_READ_GAMMA_SUPPORTED
   png_destroy_gamma_table(png_ptr);
#endif

   png_free(png_ptr, png_ptr->zbuf);
   png_free(png_ptr, png_ptr->big_row_buf);
   png_free(png_ptr, png_ptr->big_prev_row);
   png_free(png_ptr, png_ptr->chunkdata);

#ifdef PNG_READ_QUANTIZE_SUPPORTED
   png_free(png_ptr, png_ptr->palette_lookup);
   png_free(png_ptr, png_ptr->quantize_index);
#endif

   if (png_ptr->free_me & PNG_FREE_PLTE)
      png_zfree(png_ptr, png_ptr->palette);
   png_ptr->free_me &= ~PNG_FREE_PLTE;

#if defined(PNG_tRNS_SUPPORTED) || \
    defined(PNG_READ_EXPAND_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
   if (png_ptr->free_me & PNG_FREE_TRNS)
      png_free(png_ptr, png_ptr->trans_alpha);
   png_ptr->free_me &= ~PNG_FREE_TRNS;
#endif

#ifdef PNG_READ_hIST_SUPPORTED
   if (png_ptr->free_me & PNG_FREE_HIST)
      png_free(png_ptr, png_ptr->hist);
   png_ptr->free_me &= ~PNG_FREE_HIST;
#endif

   inflateEnd(&png_ptr->zstream);

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
   png_free(png_ptr, png_ptr->save_buffer);
#endif

   /* Save the important info out of the png_struct, in case it is
    * being used again.
    */
#ifdef PNG_SETJMP_SUPPORTED
   png_memcpy(tmp_jmp, png_ptr->longjmp_buffer, png_sizeof(jmp_buf));
#endif

   error_fn = png_ptr->error_fn;
#ifdef PNG_WARNINGS_SUPPORTED
   warning_fn = png_ptr->warning_fn;
#endif
   error_ptr = png_ptr->error_ptr;
#ifdef PNG_USER_MEM_SUPPORTED
   free_fn = png_ptr->free_fn;
#endif

   png_memset(png_ptr, 0, png_sizeof(png_struct));

   png_ptr->error_fn = error_fn;
#ifdef PNG_WARNINGS_SUPPORTED
   png_ptr->warning_fn = warning_fn;
#endif
   png_ptr->error_ptr = error_ptr;
#ifdef PNG_USER_MEM_SUPPORTED
   png_ptr->free_fn = free_fn;
#endif

#ifdef PNG_SETJMP_SUPPORTED
   png_memcpy(png_ptr->longjmp_buffer, tmp_jmp, png_sizeof(jmp_buf));
#endif

}

void PNGAPI
png_set_read_status_fn(png_structp png_ptr, png_read_status_ptr read_row_fn)
{
   if (png_ptr == NULL)
      return;

   png_ptr->read_row_fn = read_row_fn;
}


#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
#ifdef PNG_INFO_IMAGE_SUPPORTED
void PNGAPI
png_read_png(png_structp png_ptr, png_infop info_ptr,
                           int transforms,
                           voidp params)
{
   int row;

   if (png_ptr == NULL || info_ptr == NULL)
      return;

   /* png_read_info() gives us all of the information from the
    * PNG file before the first IDAT (image data chunk).
    */
   png_read_info(png_ptr, info_ptr);
   if (info_ptr->height > PNG_UINT_32_MAX/png_sizeof(png_bytep))
      png_error(png_ptr, "Image is too high to process with png_read_png()");

   /* -------------- image transformations start here ------------------- */

#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
   /* Tell libpng to strip 16-bit/color files down to 8 bits per color.
    */
   if (transforms & PNG_TRANSFORM_SCALE_16)
   {
     /* Added at libpng-1.5.4. "strip_16" produces the same result that it
      * did in earlier versions, while "scale_16" is now more accurate.
      */
      png_set_scale_16(png_ptr);
   }
#endif

#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
   /* If both SCALE and STRIP are required pngrtran will effectively cancel the
    * latter by doing SCALE first.  This is ok and allows apps not to check for
    * which is supported to get the right answer.
    */
   if (transforms & PNG_TRANSFORM_STRIP_16)
      png_set_strip_16(png_ptr);
#endif

#ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
   /* Strip alpha bytes from the input data without combining with
    * the background (not recommended).
    */
   if (transforms & PNG_TRANSFORM_STRIP_ALPHA)
      png_set_strip_alpha(png_ptr);
#endif

#if defined(PNG_READ_PACK_SUPPORTED) && !defined(PNG_READ_EXPAND_SUPPORTED)
   /* Extract multiple pixels with bit depths of 1, 2, or 4 from a single
    * byte into separate bytes (useful for paletted and grayscale images).
    */
   if (transforms & PNG_TRANSFORM_PACKING)
      png_set_packing(png_ptr);
#endif

#ifdef PNG_READ_PACKSWAP_SUPPORTED
   /* Change the order of packed pixels to least significant bit first
    * (not useful if you are using png_set_packing).
    */
   if (transforms & PNG_TRANSFORM_PACKSWAP)
      png_set_packswap(png_ptr);
#endif

#ifdef PNG_READ_EXPAND_SUPPORTED
   /* Expand paletted colors into true RGB triplets
    * Expand grayscale images to full 8 bits from 1, 2, or 4 bits/pixel
    * Expand paletted or RGB images with transparency to full alpha
    * channels so the data will be available as RGBA quartets.
    */
   if (transforms & PNG_TRANSFORM_EXPAND)
      if ((png_ptr->bit_depth < 8) ||
          (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE) ||
          (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)))
         png_set_expand(png_ptr);
#endif

   /* We don't handle background color or gamma transformation or quantizing.
    */

#ifdef PNG_READ_INVERT_SUPPORTED
   /* Invert monochrome files to have 0 as white and 1 as black
    */
   if (transforms & PNG_TRANSFORM_INVERT_MONO)
      png_set_invert_mono(png_ptr);
#endif

#ifdef PNG_READ_SHIFT_SUPPORTED
   /* If you want to shift the pixel values from the range [0,255] or
    * [0,65535] to the original [0,7] or [0,31], or whatever range the
    * colors were originally in:
    */
   if ((transforms & PNG_TRANSFORM_SHIFT)
       && png_get_valid(png_ptr, info_ptr, PNG_INFO_sBIT))
   {
      png_color_8p sig_bit;

      png_get_sBIT(png_ptr, info_ptr, &sig_bit);
      png_set_shift(png_ptr, sig_bit);
   }
#endif

#ifdef PNG_READ_BGR_SUPPORTED
   /* Flip the RGB pixels to BGR (or RGBA to BGRA) */
   if (transforms & PNG_TRANSFORM_BGR)
      png_set_bgr(png_ptr);
#endif

#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
   /* Swap the RGBA or GA data to ARGB or AG (or BGRA to ABGR) */
   if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
      png_set_swap_alpha(png_ptr);
#endif

#ifdef PNG_READ_SWAP_SUPPORTED
   /* Swap bytes of 16-bit files to least significant byte first */
   if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
      png_set_swap(png_ptr);
#endif

/* Added at libpng-1.2.41 */
#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
   /* Invert the alpha channel from opacity to transparency */
   if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
      png_set_invert_alpha(png_ptr);
#endif

/* Added at libpng-1.2.41 */
#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
   /* Expand grayscale image to RGB */
   if (transforms & PNG_TRANSFORM_GRAY_TO_RGB)
      png_set_gray_to_rgb(png_ptr);
#endif

/* Added at libpng-1.5.4 */
#ifdef PNG_READ_EXPAND_16_SUPPORTED
   if (transforms & PNG_TRANSFORM_EXPAND_16)
      png_set_expand_16(png_ptr);
#endif

   /* We don't handle adding filler bytes */

   /* We use png_read_image and rely on that for interlace handling, but we also
    * call png_read_update_info therefore must turn on interlace handling now:
    */
   (void)png_set_interlace_handling(png_ptr);

   /* Optional call to gamma correct and add the background to the palette
    * and update info structure.  REQUIRED if you are expecting libpng to
    * update the palette for you (i.e., you selected such a transform above).
    */
   png_read_update_info(png_ptr, info_ptr);

   /* -------------- image transformations end here ------------------- */

   png_free_data(png_ptr, info_ptr, PNG_FREE_ROWS, 0);
   if (info_ptr->row_pointers == NULL)
   {
      png_uint_32 iptr;

      info_ptr->row_pointers = (png_bytepp)png_malloc(png_ptr,
          info_ptr->height * png_sizeof(png_bytep));
      for (iptr=0; iptr<info_ptr->height; iptr++)
         info_ptr->row_pointers[iptr] = NULL;

      info_ptr->free_me |= PNG_FREE_ROWS;

      for (row = 0; row < (int)info_ptr->height; row++)
         info_ptr->row_pointers[row] = (png_bytep)png_malloc(png_ptr,
            png_get_rowbytes(png_ptr, info_ptr));
   }

   png_read_image(png_ptr, info_ptr->row_pointers);
   info_ptr->valid |= PNG_INFO_IDAT;

   /* Read rest of file, and get additional chunks in info_ptr - REQUIRED */
   png_read_end(png_ptr, info_ptr);

   PNG_UNUSED(transforms)   /* Quiet compiler warnings */
   PNG_UNUSED(params)

}
#endif /* PNG_INFO_IMAGE_SUPPORTED */
#endif /* PNG_SEQUENTIAL_READ_SUPPORTED */
#endif /* PNG_READ_SUPPORTED */