This file is indexed.

/usr/include/dlib/pixel.h is in libdlib-dev 18.18-2build1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   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
// Copyright (C) 2006  Davis E. King (davis@dlib.net)
// License: Boost Software License   See LICENSE.txt for the full license.
#ifndef DLIB_PIXEl_ 
#define DLIB_PIXEl_

#include <iostream>
#include "serialize.h"
#include <cmath>
#include "algs.h"
#include "uintn.h"
#include <limits>
#include <complex>
#include "enable_if.h"

namespace dlib
{

// ----------------------------------------------------------------------------------------

    /*!
        This file contains definitions of pixel objects and related classes and
        functionality.
    !*/

// ----------------------------------------------------------------------------------------

    template <typename T>
    struct pixel_traits;
    /*!
        WHAT THIS OBJECT REPRESENTS
            As the name implies, this is a traits class for pixel types.
            It defines the properties of a pixel.

        This traits class will define the following public static members:
            - bool grayscale
            - bool rgb
            - bool rgb_alpha
            - bool hsi

            - bool has_alpha

            - long num 

            - basic_pixel_type
            - basic_pixel_type min()
            - basic_pixel_type max()
            - is_unsigned

        The above public constants are subject to the following constraints:
            - only one of grayscale, rgb, rgb_alpha, or hsi is true
            - if (rgb == true) then
                - The type T will be a struct with 3 public members of type 
                  unsigned char named "red" "green" and "blue".  
                - This type of pixel represents the RGB color space.
                - num == 3
                - has_alpha == false
                - basic_pixel_type == unsigned char
                - min() == 0 
                - max() == 255
                - is_unsigned == true
            - if (rgb_alpha == true) then
                - The type T will be a struct with 4 public members of type 
                  unsigned char named "red" "green" "blue" and "alpha".  
                - This type of pixel represents the RGB color space with
                  an alpha channel where an alpha of 0 represents a pixel
                  that is totally transparent and 255 represents a pixel 
                  with maximum opacity.
                - num == 4
                - has_alpha == true 
                - basic_pixel_type == unsigned char
                - min() == 0 
                - max() == 255
                - is_unsigned == true
            - else if (hsi == true) then
                - The type T will be a struct with 3 public members of type
                  unsigned char named "h" "s" and "i".  
                - This type of pixel represents the HSI color space.
                - num == 3
                - has_alpha == false 
                - basic_pixel_type == unsigned char
                - min() == 0 
                - max() == 255
                - is_unsigned == true
            - else
                - grayscale == true
                - This type of pixel represents a grayscale color space.  T 
                  will be some kind of basic scalar type such as unsigned int.
                - num == 1
                - has_alpha == false 
                - basic_pixel_type == T 
                - min() == the minimum obtainable value of objects of type T 
                - max() == the maximum obtainable value of objects of type T 
                - is_unsigned is true if min() == 0 and false otherwise
    !*/

// ----------------------------------------------------------------------------------------

    struct rgb_pixel
    {
        /*!
            WHAT THIS OBJECT REPRESENTS
                This is a simple struct that represents an RGB colored graphical pixel.
        !*/

        rgb_pixel (
        ) {}

        rgb_pixel (
            unsigned char red_,
            unsigned char green_,
            unsigned char blue_
        ) : red(red_), green(green_), blue(blue_) {}

        unsigned char red;
        unsigned char green;
        unsigned char blue;
    };

// ----------------------------------------------------------------------------------------

    struct bgr_pixel
    {
        /*!
            WHAT THIS OBJECT REPRESENTS
                This is a simple struct that represents an BGR colored graphical pixel.
                (the reason it exists in addition to the rgb_pixel is so you can lay
                it down on top of a memory region that organizes its color data in the
                BGR format and still be able to read it)
        !*/

        bgr_pixel (
        ) {}

        bgr_pixel (
            unsigned char blue_,
            unsigned char green_,
            unsigned char red_
        ) : blue(blue_), green(green_), red(red_) {}

        unsigned char blue;
        unsigned char green;
        unsigned char red;
    };

// ----------------------------------------------------------------------------------------

    struct rgb_alpha_pixel
    {
        /*!
            WHAT THIS OBJECT REPRESENTS
                This is a simple struct that represents an RGB colored graphical pixel
                with an alpha channel.
        !*/

        rgb_alpha_pixel (
        ) {}

        rgb_alpha_pixel (
            unsigned char red_,
            unsigned char green_,
            unsigned char blue_,
            unsigned char alpha_
        ) : red(red_), green(green_), blue(blue_), alpha(alpha_) {}

        unsigned char red;
        unsigned char green;
        unsigned char blue;
        unsigned char alpha;
    };

// ----------------------------------------------------------------------------------------

    struct hsi_pixel
    {
        /*!
            WHAT THIS OBJECT REPRESENTS
                This is a simple struct that represents an HSI colored graphical pixel.
        !*/

        hsi_pixel (
        ) {}

        hsi_pixel (
            unsigned char h_,
            unsigned char s_,
            unsigned char i_
        ) : h(h_), s(s_), i(i_) {}

        unsigned char h;
        unsigned char s;
        unsigned char i;
    };

// ----------------------------------------------------------------------------------------

    template <
        typename P1,
        typename P2  
        >
    inline void assign_pixel (
        P1& dest,
        const P2& src
    );
    /*!
        requires
            - pixel_traits<P1> must be defined
            - pixel_traits<P2> must be defined
        ensures
            - if (P1 and P2 are the same type of pixel) then
                - simply copies the value of src into dest.  In other words,
                  dest will be identical to src after this function returns.
            - else if (P1 and P2 are not the same type of pixel) then
                - assigns pixel src to pixel dest and does any necessary color space
                  conversions.   
                - When converting from a grayscale color space with more than 255 values the
                  pixel intensity is saturated at pixel_traits<P1>::max() or pixel_traits<P1>::min()
                  as appropriate.
                - if (the dest pixel has an alpha channel and the src pixel doesn't) then
                    - #dest.alpha == 255 
                - else if (the src pixel has an alpha channel but the dest pixel doesn't) then
                    - #dest == the original dest value blended with the src value according
                      to the alpha channel in src.  
                      (i.e.  #dest == src*(alpha/255) + dest*(1-alpha/255))
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename P
        >
    inline typename pixel_traits<P>::basic_pixel_type get_pixel_intensity (
        const P& src
    );
    /*!
        requires
            - pixel_traits<P> must be defined
        ensures
            - if (pixel_traits<P>::grayscale == true) then
                - returns src
            - else
                - converts src to grayscale and returns the resulting value.
    !*/

// ----------------------------------------------------------------------------------------

    template <
        typename P,
        typename T
        >
    inline void assign_pixel_intensity (
        P& dest,
        const T& new_intensity
    );
    /*!
        requires
            - pixel_traits<P> must be defined
            - pixel_traits<T> must be defined
        ensures
            - This function changes the intensity of the dest pixel. So if the pixel in 
              question is a grayscale pixel then it simply assigns that pixel with the 
              value of get_pixel_intensity(new_intensity).  However, if the pixel is not 
              a grayscale pixel then it converts the pixel to the HSI color space and sets 
              the I channel to the given intensity and then converts this HSI value back to 
              the original pixel's color space.
            - Note that we don't necessarily have #get_pixel_intensity(dest) == get_pixel_intensity(new_intensity) 
              due to vagaries of how converting to and from HSI works out.
            - if (the dest pixel has an alpha channel) then
                - #dest.alpha == dest.alpha
    !*/

// ----------------------------------------------------------------------------------------

    inline void serialize (
        const rgb_pixel& item, 
        std::ostream& out 
    );   
    /*!
        provides serialization support for the rgb_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        rgb_pixel& item, 
        std::istream& in
    );   
    /*!
        provides deserialization support for the rgb_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    inline void serialize (
        const bgr_pixel& item, 
        std::ostream& out 
    );   
    /*!
        provides serialization support for the bgr_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        bgr_pixel& item, 
        std::istream& in
    );   
    /*!
        provides deserialization support for the bgr_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    inline void serialize (
        const rgb_alpha_pixel& item, 
        std::ostream& out 
    );   
    /*!
        provides serialization support for the rgb_alpha_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        rgb_alpha_pixel& item, 
        std::istream& in
    );   
    /*!
        provides deserialization support for the rgb_alpha_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    inline void serialize (
        const hsi_pixel& item, 
        std::ostream& out 
    );   
    /*!
        provides serialization support for the hsi_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        hsi_pixel& item, 
        std::istream& in
    );   
    /*!
        provides deserialization support for the hsi_pixel struct
    !*/

// ----------------------------------------------------------------------------------------

    template <>
    struct pixel_traits<rgb_pixel>
    {
        const static bool rgb  = true;
        const static bool rgb_alpha  = false;
        const static bool grayscale = false;
        const static bool hsi = false;
        const static long num = 3;
        typedef unsigned char basic_pixel_type;
        static basic_pixel_type min() { return 0;}
        static basic_pixel_type max() { return 255;}
        const static bool is_unsigned = true;
        const static bool has_alpha = false;
    };

// ----------------------------------------------------------------------------------------

    template <>
    struct pixel_traits<bgr_pixel>
    {
        const static bool rgb  = true;
        const static bool rgb_alpha  = false;
        const static bool grayscale = false;
        const static bool hsi = false;
        const static long num = 3;
        typedef unsigned char basic_pixel_type;
        static basic_pixel_type min() { return 0;}
        static basic_pixel_type max() { return 255;}
        const static bool is_unsigned = true;
        const static bool has_alpha = false;
    };

// ----------------------------------------------------------------------------------------

    template <>
    struct pixel_traits<rgb_alpha_pixel>
    {
        const static bool rgb  = false;
        const static bool rgb_alpha  = true;
        const static bool grayscale = false;
        const static bool hsi = false;
        const static long num = 4;
        typedef unsigned char basic_pixel_type;
        static basic_pixel_type min() { return 0;}
        static basic_pixel_type max() { return 255;}
        const static bool is_unsigned = true;
        const static bool has_alpha = true;
    };

// ----------------------------------------------------------------------------------------


    template <>
    struct pixel_traits<hsi_pixel>
    {
        const static bool rgb  = false;
        const static bool rgb_alpha  = false;
        const static bool grayscale = false;
        const static bool hsi = true;
        const static long num = 3;
        typedef unsigned char basic_pixel_type;
        static basic_pixel_type min() { return 0;}
        static basic_pixel_type max() { return 255;}
        const static bool is_unsigned = true;
        const static bool has_alpha = false;
    };

// ----------------------------------------------------------------------------------------

    template <typename T>
    struct grayscale_pixel_traits
    {
        const static bool rgb  = false;
        const static bool rgb_alpha  = false;
        const static bool grayscale = true;
        const static bool hsi = false;
        const static long num = 1;
        const static bool has_alpha = false;
        typedef T basic_pixel_type;
        static basic_pixel_type min() { return std::numeric_limits<T>::min();}
        static basic_pixel_type max() { return std::numeric_limits<T>::max();}
        const static bool is_unsigned = is_unsigned_type<T>::value;
    };

    template <> struct pixel_traits<unsigned char>  : public grayscale_pixel_traits<unsigned char> {};
    template <> struct pixel_traits<unsigned short> : public grayscale_pixel_traits<unsigned short> {};
    template <> struct pixel_traits<unsigned int>   : public grayscale_pixel_traits<unsigned int> {};
    template <> struct pixel_traits<unsigned long>  : public grayscale_pixel_traits<unsigned long> {};

    template <> struct pixel_traits<char>           : public grayscale_pixel_traits<char> {};
    template <> struct pixel_traits<signed char>    : public grayscale_pixel_traits<signed char> {};
    template <> struct pixel_traits<short>          : public grayscale_pixel_traits<short> {};
    template <> struct pixel_traits<int>            : public grayscale_pixel_traits<int> {};
    template <> struct pixel_traits<long>           : public grayscale_pixel_traits<long> {};

    template <> struct pixel_traits<int64>          : public grayscale_pixel_traits<int64> {};
    template <> struct pixel_traits<uint64>         : public grayscale_pixel_traits<uint64> {};

// ----------------------------------------------------------------------------------------

    template <typename T>
    struct float_grayscale_pixel_traits
    {
        const static bool rgb  = false;
        const static bool rgb_alpha  = false;
        const static bool grayscale = true;
        const static bool hsi = false;
        const static long num = 1;
        const static bool has_alpha = false;
        typedef T basic_pixel_type;
        static basic_pixel_type min() { return -std::numeric_limits<T>::max();}
        static basic_pixel_type max() { return std::numeric_limits<T>::max();}
        const static bool is_unsigned = false;
    };

    template <> struct pixel_traits<float>          : public float_grayscale_pixel_traits<float> {};
    template <> struct pixel_traits<double>         : public float_grayscale_pixel_traits<double> {};
    template <> struct pixel_traits<long double>    : public float_grayscale_pixel_traits<long double> {};

    // These are here mainly so you can easily copy images into complex arrays.  This is
    // useful when you want to do a FFT on an image or some similar operation.
    template <> struct pixel_traits<std::complex<float> > :       public float_grayscale_pixel_traits<float> {};
    template <> struct pixel_traits<std::complex<double> > :      public float_grayscale_pixel_traits<double> {};
    template <> struct pixel_traits<std::complex<long double> > : public float_grayscale_pixel_traits<long double> {};

// ----------------------------------------------------------------------------------------

    // The following is a bunch of conversion stuff for the assign_pixel function.

    namespace assign_pixel_helpers
    {

    // -----------------------------
        // all the same kind 

        template < typename P >
        typename enable_if_c<pixel_traits<P>::grayscale>::type
        assign(P& dest, const P& src) 
        { 
            dest = src;
        }

    // -----------------------------

        template <typename T>
        typename unsigned_type<T>::type make_unsigned (
            const T& val
        ) { return static_cast<typename unsigned_type<T>::type>(val); }

        inline float make_unsigned(const float& val) { return val; }
        inline double make_unsigned(const double& val) { return val; }
        inline long double make_unsigned(const long double& val) { return val; }


        template <typename T, typename P>
        typename enable_if_c<pixel_traits<T>::is_unsigned == pixel_traits<P>::is_unsigned, bool>::type less_or_equal_to_max (
            const P& p
        ) 
        /*!
            ensures
                - returns true if p is <= max value of T
        !*/
        { 
            return p <= pixel_traits<T>::max();         
        }

        template <typename T, typename P>
        typename enable_if_c<pixel_traits<T>::is_unsigned && !pixel_traits<P>::is_unsigned, bool>::type less_or_equal_to_max (
            const P& p
        ) 
        { 
            if (p <= 0)
                return true;
            else if (make_unsigned(p) <= pixel_traits<T>::max())
                return true;
            else
                return false;
        }

        template <typename T, typename P>
        typename enable_if_c<!pixel_traits<T>::is_unsigned && pixel_traits<P>::is_unsigned, bool>::type less_or_equal_to_max (
            const P& p
        ) 
        { 
            return p <= make_unsigned(pixel_traits<T>::max());
        }

    // -----------------------------

        template <typename T, typename P>
        typename enable_if_c<pixel_traits<P>::is_unsigned, bool >::type greater_or_equal_to_min (
            const P& 
        ) { return true; }
        /*!
            ensures
                - returns true if p is >= min value of T
        !*/

        template <typename T, typename P>
        typename enable_if_c<!pixel_traits<P>::is_unsigned && pixel_traits<T>::is_unsigned, bool >::type greater_or_equal_to_min (
            const P& p
        ) 
        { 
            return p >= 0;
        }

        template <typename T, typename P>
        typename enable_if_c<!pixel_traits<P>::is_unsigned && !pixel_traits<T>::is_unsigned, bool >::type greater_or_equal_to_min (
            const P& p
        ) 
        { 
            return p >= pixel_traits<T>::min();
        }
    // -----------------------------

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::grayscale && pixel_traits<P2>::grayscale>::type
        assign(P1& dest, const P2& src) 
        { 
            /*
                The reason for these weird comparison functions is to avoid getting compiler
                warnings about comparing signed types to unsigned and stuff like that.  
            */

            if (less_or_equal_to_max<P1>(src))
                if (greater_or_equal_to_min<P1>(src))
                    dest = static_cast<P1>(src);
                else
                    dest = pixel_traits<P1>::min();
            else
                dest = pixel_traits<P1>::max();
        }

    // -----------------------------
    // -----------------------------
    // -----------------------------

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb && pixel_traits<P2>::rgb>::type
        assign(P1& dest, const P2& src) 
        { 
            dest.red = src.red; 
            dest.green = src.green; 
            dest.blue = src.blue; 
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb_alpha && pixel_traits<P2>::rgb_alpha>::type
        assign(P1& dest, const P2& src) 
        { 
            dest.red = src.red; 
            dest.green = src.green; 
            dest.blue = src.blue; 
            dest.alpha = src.alpha; 
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::hsi && pixel_traits<P2>::hsi>::type
        assign(P1& dest, const P2& src) 
        { 
            dest.h = src.h; 
            dest.s = src.s; 
            dest.i = src.i; 
        }

    // -----------------------------
        // dest is a grayscale

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::grayscale && pixel_traits<P2>::rgb>::type
        assign(P1& dest, const P2& src) 
        { 
            const unsigned int temp = ((static_cast<unsigned int>(src.red) +
                                        static_cast<unsigned int>(src.green) +  
                                        static_cast<unsigned int>(src.blue))/3);
            assign_pixel(dest, temp);
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::grayscale && pixel_traits<P2>::rgb_alpha>::type
        assign(P1& dest, const P2& src) 
        { 

            const unsigned char avg = static_cast<unsigned char>((static_cast<unsigned int>(src.red) +
                                                                  static_cast<unsigned int>(src.green) +  
                                                                  static_cast<unsigned int>(src.blue))/3); 

            if (src.alpha == 255)
            {
                assign_pixel(dest, avg);
            }
            else
            {
                // perform this assignment using fixed point arithmetic: 
                // dest = src*(alpha/255) + dest*(1 - alpha/255);
                // dest = src*(alpha/255) + dest*1 - dest*(alpha/255);
                // dest = dest*1 + src*(alpha/255) - dest*(alpha/255);
                // dest = dest*1 + (src - dest)*(alpha/255);
                // dest += (src - dest)*(alpha/255);

                int temp = avg;
                // copy dest into dest_copy using assign_pixel to avoid potential
                // warnings about implicit float to int warnings.
                int dest_copy;
                assign_pixel(dest_copy, dest);

                temp -= dest_copy;

                temp *= src.alpha;

                temp /= 255;

                assign_pixel(dest, temp+dest_copy);
            }
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::grayscale && pixel_traits<P2>::hsi>::type
        assign(P1& dest, const P2& src) 
        { 
            assign_pixel(dest, src.i);
        }


    // -----------------------------

        struct HSL
        {
            double h;
            double s;
            double l;
        };

        struct COLOUR
        {
            double r;
            double g;
            double b;
        };

        /*
            I found this excellent bit of code for dealing with HSL spaces at 
            http://local.wasp.uwa.edu.au/~pbourke/colour/hsl/
        */
        /*
            Calculate HSL from RGB
            Hue is in degrees
            Lightness is between 0 and 1
            Saturation is between 0 and 1
        */
        inline HSL RGB2HSL(COLOUR c1)
        {
            double themin,themax,delta;
            HSL c2;
            using namespace std;

            themin = std::min(c1.r,std::min(c1.g,c1.b));
            themax = std::max(c1.r,std::max(c1.g,c1.b));
            delta = themax - themin;
            c2.l = (themin + themax) / 2;
            c2.s = 0;
            if (c2.l > 0 && c2.l < 1)
                c2.s = delta / (c2.l < 0.5 ? (2*c2.l) : (2-2*c2.l));
            c2.h = 0;
            if (delta > 0) {
                if (themax == c1.r && themax != c1.g)
                    c2.h += (c1.g - c1.b) / delta;
                if (themax == c1.g && themax != c1.b)
                    c2.h += (2 + (c1.b - c1.r) / delta);
                if (themax == c1.b && themax != c1.r)
                    c2.h += (4 + (c1.r - c1.g) / delta);
                c2.h *= 60;
            }
            return(c2);
        }

        /*
            Calculate RGB from HSL, reverse of RGB2HSL()
            Hue is in degrees
            Lightness is between 0 and 1
            Saturation is between 0 and 1
        */
        inline COLOUR HSL2RGB(HSL c1)
        {
            COLOUR c2,sat,ctmp;
            using namespace std;

            if (c1.h < 120) {
                sat.r = (120 - c1.h) / 60.0;
                sat.g = c1.h / 60.0;
                sat.b = 0;
            } else if (c1.h < 240) {
                sat.r = 0;
                sat.g = (240 - c1.h) / 60.0;
                sat.b = (c1.h - 120) / 60.0;
            } else {
                sat.r = (c1.h - 240) / 60.0;
                sat.g = 0;
                sat.b = (360 - c1.h) / 60.0;
            }
            sat.r = std::min(sat.r,1.0);
            sat.g = std::min(sat.g,1.0);
            sat.b = std::min(sat.b,1.0);

            ctmp.r = 2 * c1.s * sat.r + (1 - c1.s);
            ctmp.g = 2 * c1.s * sat.g + (1 - c1.s);
            ctmp.b = 2 * c1.s * sat.b + (1 - c1.s);

            if (c1.l < 0.5) {
                c2.r = c1.l * ctmp.r;
                c2.g = c1.l * ctmp.g;
                c2.b = c1.l * ctmp.b;
            } else {
                c2.r = (1 - c1.l) * ctmp.r + 2 * c1.l - 1;
                c2.g = (1 - c1.l) * ctmp.g + 2 * c1.l - 1;
                c2.b = (1 - c1.l) * ctmp.b + 2 * c1.l - 1;
            }

            return(c2);
        }


    // -----------------------------
        // dest is a color rgb_pixel

        template < typename P1 >
        typename enable_if_c<pixel_traits<P1>::rgb>::type
        assign(P1& dest, const unsigned char& src) 
        { 
            dest.red = src; 
            dest.green = src; 
            dest.blue = src; 
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb && pixel_traits<P2>::grayscale>::type
        assign(P1& dest, const P2& src) 
        { 
            unsigned char p;
            assign_pixel(p, src);
            dest.red = p; 
            dest.green = p; 
            dest.blue = p; 
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb && pixel_traits<P2>::rgb_alpha>::type
        assign(P1& dest, const P2& src) 
        { 
            if (src.alpha == 255)
            {
                dest.red = src.red;
                dest.green = src.green;
                dest.blue = src.blue;
            }
            else
            {
                // perform this assignment using fixed point arithmetic: 
                // dest = src*(alpha/255) + dest*(1 - alpha/255);
                // dest = src*(alpha/255) + dest*1 - dest*(alpha/255);
                // dest = dest*1 + src*(alpha/255) - dest*(alpha/255);
                // dest = dest*1 + (src - dest)*(alpha/255);
                // dest += (src - dest)*(alpha/255);

                unsigned int temp_r = src.red;
                unsigned int temp_g = src.green;
                unsigned int temp_b = src.blue;

                temp_r -= dest.red;
                temp_g -= dest.green;
                temp_b -= dest.blue;

                temp_r *= src.alpha;
                temp_g *= src.alpha;
                temp_b *= src.alpha;

                temp_r >>= 8;
                temp_g >>= 8;
                temp_b >>= 8;

                dest.red += static_cast<unsigned char>(temp_r&0xFF);
                dest.green += static_cast<unsigned char>(temp_g&0xFF);
                dest.blue += static_cast<unsigned char>(temp_b&0xFF);
            }
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb && pixel_traits<P2>::hsi>::type
        assign(P1& dest, const P2& src) 
        { 
            COLOUR c;
            HSL h;
            h.h = src.h;
            h.h = h.h/255.0*360;
            h.s = src.s/255.0;
            h.l = src.i/255.0;
            c = HSL2RGB(h);

            dest.red = static_cast<unsigned char>(c.r*255.0 + 0.5);
            dest.green = static_cast<unsigned char>(c.g*255.0 + 0.5);
            dest.blue = static_cast<unsigned char>(c.b*255.0 + 0.5);
        }

    // -----------------------------
    // dest is a color rgb_alpha_pixel

        template < typename P1 >
        typename enable_if_c<pixel_traits<P1>::rgb_alpha>::type
        assign(P1& dest, const unsigned char& src) 
        { 
            dest.red = src; 
            dest.green = src; 
            dest.blue = src; 
            dest.alpha = 255;
        }


        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb_alpha && pixel_traits<P2>::grayscale>::type
        assign(P1& dest, const P2& src) 
        { 
            unsigned char p;
            assign_pixel(p, src);

            dest.red = p; 
            dest.green = p; 
            dest.blue = p; 
            dest.alpha = 255;
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb_alpha && pixel_traits<P2>::rgb>::type
        assign(P1& dest, const P2& src) 
        { 
            dest.red = src.red;
            dest.green = src.green;
            dest.blue = src.blue;
            dest.alpha = 255;
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::rgb_alpha && pixel_traits<P2>::hsi>::type
        assign(P1& dest, const P2& src) 
        { 
            COLOUR c;
            HSL h;
            h.h = src.h;
            h.h = h.h/255.0*360;
            h.s = src.s/255.0;
            h.l = src.i/255.0;
            c = HSL2RGB(h);

            dest.red = static_cast<unsigned char>(c.r*255.0 + 0.5);
            dest.green = static_cast<unsigned char>(c.g*255.0 + 0.5);
            dest.blue = static_cast<unsigned char>(c.b*255.0 + 0.5);
            dest.alpha = 255;
        }

    // -----------------------------
        // dest is an hsi pixel

        template < typename P1>
        typename enable_if_c<pixel_traits<P1>::hsi>::type
        assign(P1& dest, const unsigned char& src) 
        { 
            dest.h = 0;
            dest.s = 0;
            dest.i = src;
        }


        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::hsi && pixel_traits<P2>::grayscale>::type
        assign(P1& dest, const P2& src) 
        { 
            dest.h = 0;
            dest.s = 0;
            assign_pixel(dest.i, src);
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::hsi && pixel_traits<P2>::rgb>::type
        assign(P1& dest, const P2& src) 
        { 
            COLOUR c1;
            HSL c2;
            c1.r = src.red/255.0;
            c1.g = src.green/255.0;
            c1.b = src.blue/255.0;
            c2 = RGB2HSL(c1);

            dest.h = static_cast<unsigned char>(c2.h/360.0*255.0 + 0.5);
            dest.s = static_cast<unsigned char>(c2.s*255.0 + 0.5);
            dest.i = static_cast<unsigned char>(c2.l*255.0 + 0.5);
        }

        template < typename P1, typename P2 >
        typename enable_if_c<pixel_traits<P1>::hsi && pixel_traits<P2>::rgb_alpha>::type
        assign(P1& dest, const P2& src) 
        { 
            rgb_pixel temp;
            // convert target hsi pixel to rgb
            assign_pixel_helpers::assign(temp,dest);

            // now assign the rgb_alpha value to our temp rgb pixel
            assign_pixel_helpers::assign(temp,src);

            // now we can just go assign the new rgb value to the
            // hsi pixel
            assign_pixel_helpers::assign(dest,temp);
        }

    }

    // -----------------------------

    template < typename P1, typename P2 >
    inline void assign_pixel (
        P1& dest,
        const P2& src
    ) { assign_pixel_helpers::assign(dest,src); }

// ----------------------------------------------------------------------------------------

    template <
        typename P,
        typename T
        >
    inline typename enable_if_c<pixel_traits<P>::grayscale>::type assign_pixel_intensity_helper (
        P& dest,
        const T& new_intensity
    )
    {
        assign_pixel(dest, new_intensity);
    }

    template <
        typename P,
        typename T
        >
    inline typename enable_if_c<pixel_traits<P>::grayscale == false&&
                                pixel_traits<P>::has_alpha>::type assign_pixel_intensity_helper (
        P& dest,
        const T& new_intensity
    )
    {
        hsi_pixel p;
        const unsigned long old_alpha = dest.alpha;
        dest.alpha = 255;
        rgb_pixel temp;
        assign_pixel(temp, dest); // put dest into an rgb_pixel to avoid the somewhat complicated assign_pixel(hsi,rgb_alpha).
        assign_pixel(p,temp);
        assign_pixel(p.i, new_intensity);
        assign_pixel(dest,p);
        dest.alpha = old_alpha;
    }

    template <
        typename P,
        typename T
        >
    inline typename enable_if_c<pixel_traits<P>::grayscale == false&&
                                pixel_traits<P>::has_alpha == false>::type assign_pixel_intensity_helper (
        P& dest,
        const T& new_intensity
    )
    {
        hsi_pixel p;
        assign_pixel(p,dest);
        assign_pixel(p.i, new_intensity);
        assign_pixel(dest,p);
    }

    template <
        typename P,
        typename T
        >
    inline void assign_pixel_intensity (
        P& dest,
        const T& new_intensity
    )
    {
        assign_pixel_intensity_helper(dest, new_intensity);
    }

// ----------------------------------------------------------------------------------------

    template <
        typename P
        >
    inline typename enable_if_c<pixel_traits<P>::grayscale, P>::type get_pixel_intensity_helper (
        const P& src 
    )
    {
        return src;
    }

    template <
        typename P
        >
    inline typename enable_if_c<pixel_traits<P>::grayscale == false&&
                                pixel_traits<P>::has_alpha, 
                                typename pixel_traits<P>::basic_pixel_type>::type get_pixel_intensity_helper (
        const P& src
    )
    {
        P temp = src;
        temp.alpha = 255;
        typename pixel_traits<P>::basic_pixel_type p;
        assign_pixel(p,temp);
        return p;
    }

    template <
        typename P
        >
    inline typename enable_if_c<pixel_traits<P>::grayscale == false&&
                                pixel_traits<P>::has_alpha == false, 
                                typename pixel_traits<P>::basic_pixel_type>::type get_pixel_intensity_helper (
        const P& src
    )
    {
        typename pixel_traits<P>::basic_pixel_type p;
        assign_pixel(p,src);
        return p;
    }

    template <
        typename P
        >
    inline typename pixel_traits<P>::basic_pixel_type get_pixel_intensity (
        const P& src
    )
    {
        return get_pixel_intensity_helper(src);
    }

// ----------------------------------------------------------------------------------------
// ----------------------------------------------------------------------------------------
// ----------------------------------------------------------------------------------------

    inline void serialize (
        const rgb_alpha_pixel& item, 
        std::ostream& out 
    )   
    {
        try
        {
            serialize(item.red,out);
            serialize(item.green,out);
            serialize(item.blue,out);
            serialize(item.alpha,out);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while serializing object of type rgb_alpha_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        rgb_alpha_pixel& item, 
        std::istream& in
    )   
    {
        try
        {
            deserialize(item.red,in);
            deserialize(item.green,in);
            deserialize(item.blue,in);
            deserialize(item.alpha,in);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while deserializing object of type rgb_alpha_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

    inline void serialize (
        const rgb_pixel& item, 
        std::ostream& out 
    )   
    {
        try
        {
            serialize(item.red,out);
            serialize(item.green,out);
            serialize(item.blue,out);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while serializing object of type rgb_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        rgb_pixel& item, 
        std::istream& in
    )   
    {
        try
        {
            deserialize(item.red,in);
            deserialize(item.green,in);
            deserialize(item.blue,in);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while deserializing object of type rgb_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

    inline void serialize (
        const bgr_pixel& item, 
        std::ostream& out 
    )   
    {
        try
        {
            serialize(item.blue,out);
            serialize(item.green,out);
            serialize(item.red,out);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while serializing object of type bgr_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        bgr_pixel& item, 
        std::istream& in
    )   
    {
        try
        {
            deserialize(item.blue,in);
            deserialize(item.green,in);
            deserialize(item.red,in);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while deserializing object of type bgr_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

    inline void serialize (
        const hsi_pixel& item, 
        std::ostream& out 
    )   
    {
        try
        {
            serialize(item.h,out);
            serialize(item.s,out);
            serialize(item.i,out);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while serializing object of type hsi_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

    inline void deserialize (
        hsi_pixel& item, 
        std::istream& in
    )   
    {
        try
        {
            deserialize(item.h,in);
            deserialize(item.s,in);
            deserialize(item.i,in);
        }
        catch (serialization_error& e)
        {
            throw serialization_error(e.info + "\n   while deserializing object of type hsi_pixel"); 
        }
    }

// ----------------------------------------------------------------------------------------

}

#endif // DLIB_PIXEl_