tiffread/src/tiff/tiffread.c

#include "tiffread.h"
#include "aliases.h"
#include "endianness.h"
#include "image.h"
#include "mem_arena.h"
#include <assert.h>
#include <math.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

#define TIFF_MAGIC 0x002a

#define TIFF_FILENAME_MIN_LENGTH 6
#define TIFF_EXT_MAX_LENGTH 5
#define IS_TIFF_EXTENSION(EXT)                                                 \
  (strncmp(EXT, ".tif", 4) == 0 || strncmp(EXT, ".tiff", 5) == 0)

#define NULL_TIFF_ALPHA ((TiffAlpha){0})

#define INVALID_SAMPLE_COUNT 0
#define INVALID_ROWS_PER_STRIP 0
#define INVALID_STRIP_COUNT 0

#define INVALID_ALPHA_OFFSET -1

#define TIFF_SHORT_BYTE_COUNT field_types[TIFF_FIELD_TYPE_SHORT].byte_count
#define TIFF_LONG_BYTE_COUNT field_types[TIFF_FIELD_TYPE_LONG].byte_count

#define RGB_SAMPLE_COUNT 3
#define MIN_BITS_PER_SAMPLE 8

#define TEMP_ARENA_CAPACITY (20 * 1024 * 1024)

#define TYPE_MAX_COUNT (UINT8_MAX * sizeof(const char *))

// clang-format off
enum tiff_byte_order {
  TIFF_ORDER_LITTLE_ENDIAN = 0x4949,
  TIFF_ORDER_BIG_ENDIAN    = 0x4d4d,
};

enum tiff_public_tags {
  #include "tiff_public_tags.inc"
};

enum tiff_field_types {
  #include "tiff_field_types.inc"
};

typedef struct field_type TiffFieldType;
struct field_type {
  const char *name;
  u16 byte_count;
};

internal TiffFieldType field_types[TYPE_MAX_COUNT] = {
  #define TIFF_TYPE_LOOKUP
  #include "tiff_field_types.inc"
  #undef TIFF_TYPE_LOOKUP
};

typedef enum tiff_image_type_names {
  TIFF_IMAGE_TYPE_INVALID   = 0,
  TIFF_IMAGE_TYPE_BILEVEL   = 1,
  TIFF_IMAGE_TYPE_GRAYSCALE = TIFF_PUBLIC_TAG_BITS_PER_SAMPLE,
  TIFF_IMAGE_TYPE_PALETTE   = TIFF_PUBLIC_TAG_BITS_PER_SAMPLE | TIFF_PUBLIC_TAG_COLOR_MAP,
  TIFF_IMAGE_TYPE_RGB       = TIFF_PUBLIC_TAG_BITS_PER_SAMPLE | TIFF_PUBLIC_TAG_SAMPLES_PER_PIXEL,
} TiffImageType;

enum tiff_extra_samples {
  TIFF_EXTRA_SAMPLE_UNSPECIFIED        = 0x0000,
  TIFF_EXTRA_SAMPLE_ASSOCIATED_ALPHA   = 0x0001,
  TIFF_EXTRA_SAMPLE_UNASSOCIATED_ALPHA = 0x0002,
};

enum tiff_compression {
  TIFF_COMPRESSION_UNCOMPRESSED = 0x0001,
  TIFF_COMPRESSION_CCITT_1D     = 0x0002,
  TIFF_COMPRESSION_GROUP_3_FAX  = 0x0003,
  TIFF_COMPRESSION_GROUP_4_FAX  = 0x0004,
  TIFF_COMPRESSION_LZW          = 0x0005,
  TIFF_COMPRESSION_JPEG         = 0x0006,
  TIFF_COMPRESSION_PACK_BITS    = 0x8005,
};

enum tiff_photometric_interpretation {
  TIFF_PHOTOMETRIC_INTERPRETATION_WHITE_IS_ZERO     = 0x0000,
  TIFF_PHOTOMETRIC_INTERPRETATION_BLACK_IS_ZERO     = 0x0001,
  TIFF_PHOTOMETRIC_INTERPRETATION_RGB               = 0x0002,
  TIFF_PHOTOMETRIC_INTERPRETATION_RGB_PALETTE       = 0x0003,
  TIFF_PHOTOMETRIC_INTERPRETATION_TRANSPARENCY_MASK = 0x0004,
  TIFF_PHOTOMETRIC_INTERPRETATION_CMYK              = 0x0005,
  TIFF_PHOTOMETRIC_INTERPRETATION_YCbCr             = 0x0006,
  TIFF_PHOTOMETRIC_INTERPRETATION_CIELab            = 0x0008,

  TIFF_PHOTOMETRIC_INTERPRETATION_INVALID,
};

enum tiff_planar_configuration {
  TIFF_PLANAR_CONFIG_CHUNKY = 0x0001,
  TIFF_PLANAR_CONFIG_PLANAR = 0x0002,
};
// clang-format on

typedef struct short_long_value ShortLongValue;
struct short_long_value {
  union {
    u16 short_val;
    u32 long_val;
  };
};

typedef struct hdr TiffHdr;
struct hdr {
  u16 order;
  u16 magic;
  u32 first_ifd_offset;
};

typedef struct field TiffField;
struct field {
  u16 tag;
  u16 type;
  u32 count;
  u32 value_offset;
};

typedef struct IFD TiffIFD;
struct IFD {
  u16 count;
  TiffField *fields;
  u32 next_ifd;
};

typedef enum {
  ALPHA_TYPE_UNDEFINED = 0,
  ALPHA_TYPE_ASSOCIATED,
  ALPHA_TYPE_UNASSOCIATED,
} AlphaType;

typedef struct tiff_alpha TiffAlpha;
struct tiff_alpha {
  AlphaType type;
  u32 sample_offset;
};

typedef struct tiff_sample_bits TiffSampleBits;
struct tiff_sample_bits {
  u16 r;
  u16 g;
  u16 b;
  u16 a;
};

typedef struct tiff_strip TiffStrip;
struct tiff_strip {
  u32 offset;
  u32 byte_count;
};

typedef struct tiff_image TiffImage;
struct tiff_image {
  TiffImageType type;
  u32 image_width;
  u32 image_length;
  u32 bits_per_sample;
  u32 sample_count;
  bool bits_per_sample_offset;
  u16 compression;
  u16 photometric_interpretation;
  u16 strip_offsets_type_byte_count;
  ShortLongValue strip_offsets;
  bool strip_offsets_offset;
  u32 rows_per_strip;
  u16 strip_byte_count_type_byte_count;
  ShortLongValue strip_byte_counts;
  bool strip_byte_counts_offset;
  u32 strip_count;
  u32 color_map;
  u32 extra_samples;
  u32 extra_samples_count;
  bool extra_samples_offset;
  TiffAlpha alpha;
  TiffSampleBits rgba_bits_per_sample;
  TiffStrip *strips;
};

typedef struct tiff_reader TiffReader;
struct tiff_reader {
  FILE *fp;
  TiffHdr header;
  TiffIFD ifd;
  TiffImage img;
  Pixel *pixels;
};

typedef struct strip_data_field StripDataField;
struct strip_data_field {
  u32 *strip_value;
  const ShortLongValue *value_from_file;
  u32 strip_index;
  u32 length_in_bytes;
  u16 type_byte_count;
};

internal bool read_tiff_header(TiffReader *reader);
internal bool read_ifd(TiffReader *reader, Arena *arena);
internal bool read_ifd_fields(TiffReader *reader);
internal void read_alpha(TiffReader *reader);
internal void read_bits_per_sample(TiffReader *reader);
internal bool read_image_pixels(TiffReader *reader, Arena *arena);
internal bool read_strip_data(TiffReader *reader, Arena *arena);
internal void read_strips(TiffReader *reader);
internal void read_strip_data_field(const TiffReader *reader,
                                    StripDataField *field);
internal bool read_field(const TiffField *field, TiffImage *img);
internal bool validate_image_type(const TiffImage *img);
internal void fread_with_offset(FILE *fp, void *dst, u64 count, u64 offset);
internal bool valid_tiff_file(const char *file);

Image *read_baseline_tiff(const char *file, Arena *arena) {
  Image *img_out = NULL;

  if (!file || !arena || !valid_tiff_file(file)) {
    goto READ_BASELINE_RETURN_IMG;
  }

  TiffReader reader = {.fp = fopen(file, "rb")};
  if (!reader.fp) {
    goto READ_BASELINE_RETURN_IMG;
  }

  Arena *temp_arena = NULL;
  if (!wapp_mem_arena_init(&temp_arena, TEMP_ARENA_CAPACITY)) {
    goto READ_BASELINE_FILE_CLEANUP;
  }

  if (!read_tiff_header(&reader)) {
    goto READ_BASELINE_DESTROY_ARENA;
  }

  if (!read_ifd(&reader, temp_arena)) {
    goto READ_BASELINE_DESTROY_ARENA;
  }

  if (!read_ifd_fields(&reader)) {
    goto READ_BASELINE_DESTROY_ARENA;
  }

  assert((reader.img.type == TIFF_IMAGE_TYPE_RGB) &&
         "Currently, only RGB images are supported");

  bool image_is_8_bit =
      (reader.img.rgba_bits_per_sample.r == MIN_BITS_PER_SAMPLE &&
       reader.img.rgba_bits_per_sample.g == MIN_BITS_PER_SAMPLE &&
       reader.img.rgba_bits_per_sample.b == MIN_BITS_PER_SAMPLE &&
       reader.img.rgba_bits_per_sample.a == MIN_BITS_PER_SAMPLE);
  assert(image_is_8_bit && "Currently, only 8-bit images are supported");

  if (!read_image_pixels(&reader, temp_arena)) {
    goto READ_BASELINE_DESTROY_ARENA;
  }

  img_out = create_image(reader.img.image_width, reader.img.image_length,
                         reader.pixels, arena);

READ_BASELINE_DESTROY_ARENA:
  wapp_mem_arena_destroy(&temp_arena);

READ_BASELINE_FILE_CLEANUP:
  fclose(reader.fp);

READ_BASELINE_RETURN_IMG:
  return img_out;
}

internal bool read_tiff_header(TiffReader *reader) {
  fread_with_offset(reader->fp, &(reader->header), sizeof(TiffHdr), 0);

  switch (reader->header.order) {
  case TIFF_ORDER_LITTLE_ENDIAN:
    if (IS_BIG_ENDIAN) {
      reader->header.magic = htons(reader->header.magic);
      reader->header.first_ifd_offset = htonl(reader->header.first_ifd_offset);
    }

    break;
  case TIFF_ORDER_BIG_ENDIAN:
    if (IS_LITTLE_ENDIAN) {
      reader->header.magic = ntohs(reader->header.magic);
      reader->header.first_ifd_offset = ntohl(reader->header.first_ifd_offset);
    }

    break;
  default:
    return false;
  }

  if (reader->header.magic != TIFF_MAGIC) {
    return false;
  }

  return true;
}

internal bool read_ifd(TiffReader *reader, Arena *arena) {
  fread_with_offset(reader->fp, &(reader->ifd.count), sizeof(reader->ifd.count),
                    reader->header.first_ifd_offset);

  switch (reader->header.order) {
  case TIFF_ORDER_LITTLE_ENDIAN:
    if (IS_BIG_ENDIAN) {
      reader->ifd.count = htons(reader->ifd.count);
    }

    break;
  case TIFF_ORDER_BIG_ENDIAN:
    if (IS_LITTLE_ENDIAN) {
      reader->ifd.count = ntohs(reader->ifd.count);
    }

    break;
  }

  u64 field_byte_count = sizeof(TiffField) * reader->ifd.count;
  reader->ifd.fields =
      (TiffField *)wapp_mem_arena_alloc(arena, field_byte_count);
  if (!(reader->ifd.fields)) {
    return false;
  }

  fread(reader->ifd.fields, field_byte_count, 1, reader->fp);
  fread(&(reader->ifd.next_ifd), sizeof(reader->ifd.next_ifd), 1, reader->fp);

  return true;
}

internal bool read_ifd_fields(TiffReader *reader) {
  reader->img.type = TIFF_IMAGE_TYPE_BILEVEL;

  for (u64 i = 0; i < reader->ifd.count; ++i) {
    TiffField *field = &(reader->ifd.fields[i]);

    switch (reader->header.order) {
    case TIFF_ORDER_BIG_ENDIAN:
      if (IS_LITTLE_ENDIAN) {
        field->tag = ntohs(field->tag);
        field->type = ntohs(field->type);
        field->count = ntohl(field->count);

        if (field_types[field->type].byte_count > 2 ||
            field_types[field->type].byte_count * field->count > 4) {
          field->value_offset = ntohl(field->value_offset);
        } else {
          field->value_offset = ntohs(field->value_offset);
        }
      }
      break;
    case TIFF_ORDER_LITTLE_ENDIAN:
      if (IS_BIG_ENDIAN) {
        field->tag = htons(field->tag);
        field->type = htons(field->type);
        field->count = htonl(field->count);

        if (field_types[field->type].byte_count > 2 ||
            field_types[field->type].byte_count * field->count > 4) {
          field->value_offset = htonl(field->value_offset);
        } else {
          field->value_offset = htons(field->value_offset);
        }
      }
      break;
    }

    if (!read_field(field, &(reader->img))) {
      return false;
    }
  }

  if (!validate_image_type(&(reader->img))) {
    return false;
  }

  read_alpha(reader);
  read_bits_per_sample(reader);

#ifdef DEBUG
  // clang-format off
  printf("SIZE (width, height)                          :   %u, %u\n", reader->img.image_width, reader->img.image_length);
  printf("SAMPLES (bits per sample, count, is offset)   :   %u, %u, %u\n", reader->img.bits_per_sample, reader->img.sample_count, reader->img.bits_per_sample_offset);
  printf("EXTRA SAMPLES (samples, count, is offset)     :   %u, %u, %u\n", reader->img.extra_samples, reader->img.extra_samples_count, reader->img.extra_samples_offset);
  printf("ALPHA (type, offset)                          :   %u, %u\n", reader->img.alpha.type, reader->img.alpha.sample_offset);
  printf("SAMPLES PER PIXEL                             :   %u\n", reader->img.sample_count);
  printf("PHOTOMETRIC INTERPRETATION                    :   %u\n", reader->img.photometric_interpretation);
  printf("ROWS PER STRIP (rows, strip count)            :   %u, %u\n", reader->img.rows_per_strip, reader->img.strip_count);
  printf("STRIP OFFSETS (offsets, is offset)            :   %u, %u\n", reader->img.strip_offsets.long_val, reader->img.strip_offsets_offset);
  printf("STRIP BYTES (byte count, is offset)           :   %u, %u\n", reader->img.strip_byte_counts.long_val, reader->img.strip_byte_counts_offset);
  // clang-format on
#endif

  return true;
}

internal void read_alpha(TiffReader *reader) {
  reader->img.alpha = NULL_TIFF_ALPHA;

  if (reader->img.extra_samples_count == 0) {
    return;
  }

  u64 byte_count = TIFF_SHORT_BYTE_COUNT * reader->img.extra_samples_count;
  u16 samples[reader->img.extra_samples_count];
  memset(samples, 0, byte_count);

  if (reader->img.extra_samples_offset) {
    fread_with_offset(reader->fp, samples, byte_count,
                      reader->img.extra_samples);

    switch (reader->header.order) {
    case TIFF_ORDER_BIG_ENDIAN:
      if (IS_LITTLE_ENDIAN) {
        for (u64 i = 0; i < reader->img.extra_samples_count; ++i) {
          samples[i] = ntohs(samples[i]);
        }
      }
      break;
    case TIFF_ORDER_LITTLE_ENDIAN:
      if (IS_BIG_ENDIAN) {
        for (u64 i = 0; i < reader->img.extra_samples_count; ++i) {
          samples[i] = htons(samples[i]);
        }
      }
      break;
    }
  } else {
    memcpy(samples, &(reader->img.extra_samples), byte_count);
  }

  for (u32 i = 0; i < reader->img.extra_samples_count; ++i) {
    u16 *sample = &(samples[i]);
    if (*sample == TIFF_EXTRA_SAMPLE_ASSOCIATED_ALPHA ||
        *sample == TIFF_EXTRA_SAMPLE_UNASSOCIATED_ALPHA) {
      reader->img.alpha.type = *sample == TIFF_EXTRA_SAMPLE_ASSOCIATED_ALPHA
                                   ? ALPHA_TYPE_ASSOCIATED
                                   : ALPHA_TYPE_UNASSOCIATED;
      reader->img.alpha.sample_offset = i;
      break;
    }
  }
}

internal void read_bits_per_sample(TiffReader *reader) {
  TiffAlpha alpha = reader->img.alpha;
  u64 main_samples = reader->img.sample_count - reader->img.extra_samples_count;

  u64 byte_count = TIFF_SHORT_BYTE_COUNT * reader->img.sample_count;
  u16 bits_per_sample[reader->img.sample_count];
  memset(bits_per_sample, 0, byte_count);

  if (reader->img.bits_per_sample_offset) {
    fread_with_offset(reader->fp, bits_per_sample, byte_count,
                      reader->img.bits_per_sample);

    switch (reader->header.order) {
    case TIFF_ORDER_BIG_ENDIAN:
      if (IS_LITTLE_ENDIAN) {
        for (u64 i = 0; i < reader->img.sample_count; ++i) {
          bits_per_sample[i] = ntohs(bits_per_sample[i]);
        }
      }
      break;
    case TIFF_ORDER_LITTLE_ENDIAN:
      if (IS_BIG_ENDIAN) {
        for (u64 i = 0; i < reader->img.sample_count; ++i) {
          bits_per_sample[i] = htons(bits_per_sample[i]);
        }
      }
      break;
    }
  } else {
    memcpy(bits_per_sample, &(reader->img.bits_per_sample), byte_count);
  }

  TiffSampleBits *bits = &(reader->img.rgba_bits_per_sample);
  *bits = (TiffSampleBits){0};
  memcpy(bits, bits_per_sample, TIFF_SHORT_BYTE_COUNT * main_samples);

  // Set missing samples if image doesn't have all RGB samples
  if (main_samples < RGB_SAMPLE_COUNT) {
    u64 count = RGB_SAMPLE_COUNT - main_samples;
    for (u64 i = 0; i < count; ++i) {
      u16 *value = &(((u16 *)(&bits))[main_samples + i]);
      *value = MIN_BITS_PER_SAMPLE;
    }
  }

  if (alpha.type == ALPHA_TYPE_UNDEFINED) {
    bits->a = MIN_BITS_PER_SAMPLE;
  } else {
    void *alpha_sample = &(bits_per_sample[main_samples + alpha.sample_offset]);
    memcpy(&(bits->a), alpha_sample, TIFF_SHORT_BYTE_COUNT);
  }

  bits->r = bits->r < MIN_BITS_PER_SAMPLE ? MIN_BITS_PER_SAMPLE : bits->r;
  bits->g = bits->g < MIN_BITS_PER_SAMPLE ? MIN_BITS_PER_SAMPLE : bits->g;
  bits->b = bits->b < MIN_BITS_PER_SAMPLE ? MIN_BITS_PER_SAMPLE : bits->b;
  bits->a = bits->a < MIN_BITS_PER_SAMPLE ? MIN_BITS_PER_SAMPLE : bits->a;
}

internal bool read_image_pixels(TiffReader *reader, Arena *arena) {
  reader->pixels = NULL;
  u64 img_byte_count =
      sizeof(Pixel) * reader->img.image_width * reader->img.image_length;

  if (!read_strip_data(reader, arena)) {
    return false;
  }

#ifdef DEBUG
  for (u32 i = 0; i < reader->img.strip_count; ++i) {
    printf("%u, %u\n", reader->img.strips[i].offset,
           reader->img.strips[i].byte_count);
  }
#endif

  reader->pixels = wapp_mem_arena_alloc(arena, img_byte_count);
  if (!reader->pixels) {
    return false;
  }

  read_strips(reader);

  return true;
}

internal bool read_strip_data(TiffReader *reader, Arena *arena) {
  reader->img.strips =
      wapp_mem_arena_alloc(arena, sizeof(TiffStrip) * reader->img.strip_count);
  if (!(reader->img.strips)) {
    return false;
  }

  u32 offsets_total_bytes =
      reader->img.strip_count * reader->img.strip_offsets_type_byte_count;
  u32 byte_count_total_bytes =
      reader->img.strip_count * reader->img.strip_byte_count_type_byte_count;

  if ((!(reader->img.strip_offsets_offset) &&
       offsets_total_bytes > TIFF_LONG_BYTE_COUNT) ||
      (!(reader->img.strip_byte_counts_offset) &&
       byte_count_total_bytes > TIFF_LONG_BYTE_COUNT)) {
    return false;
  }

  u16 offset_size = reader->img.strip_offsets_type_byte_count;
  u16 counts_size = reader->img.strip_byte_count_type_byte_count;

  for (u32 i = 0; i < reader->img.strip_count; ++i) {
    TiffStrip *strip = &(reader->img.strips[i]);
    StripDataField offsets = {
        .strip_value = &(strip->offset),
        .value_from_file = &(reader->img.strip_offsets),
        .strip_index = i,
        .length_in_bytes = offsets_total_bytes,
        .type_byte_count = offset_size,
    };
    StripDataField counts = {
        .strip_value = &(strip->byte_count),
        .value_from_file = &(reader->img.strip_byte_counts),
        .strip_index = i,
        .length_in_bytes = byte_count_total_bytes,
        .type_byte_count = counts_size,
    };

    read_strip_data_field(reader, &offsets);
    read_strip_data_field(reader, &counts);
  }

  return true;
}

internal void read_strips(TiffReader *reader) {
  u64 position = 0;
  u64 main_samples = reader->img.sample_count - reader->img.extra_samples_count;
  TiffAlpha alpha = reader->img.alpha;

  Pixel *p;
  u64 start_offset;
  u64 alpha_offset;

  for (u64 i = 0; i < reader->img.strip_count; ++i) {
    const TiffStrip *strip = &(reader->img.strips[i]);

    for (u64 j = 0; j < strip->byte_count / reader->img.sample_count; ++j) {
      p = &(reader->pixels[position]);
      start_offset = strip->offset + j * reader->img.sample_count;
      alpha_offset = start_offset + main_samples + alpha.sample_offset;

      fread_with_offset(reader->fp, p, main_samples, start_offset);

      if (alpha.type == ALPHA_TYPE_UNDEFINED) {
        p->a = 255;
      } else {
        fread_with_offset(reader->fp, &(p->a), 1, alpha_offset);

        if (alpha.type == ALPHA_TYPE_UNASSOCIATED) {
          p->r *= p->a;
          p->g *= p->a;
          p->b *= p->a;
        }
      }

      ++position;
    }
  }
}

internal void read_strip_data_field(const TiffReader *reader,
                                    StripDataField *field) {
  u16 tiff_long_byte_count = field_types[TIFF_FIELD_TYPE_LONG].byte_count;

  bool value_is_file_offset = field->length_in_bytes > tiff_long_byte_count;
  u32 offset = field->type_byte_count * field->strip_index;

  if (!value_is_file_offset) {
    u8 *value = (u8 *)&(field->value_from_file->long_val);
    memcpy(field->strip_value, value + offset, field->type_byte_count);

    return;
  }

  fread_with_offset(reader->fp, field->strip_value, field->type_byte_count,
                    field->value_from_file->long_val + offset);

  switch (reader->header.order) {
  case TIFF_ORDER_BIG_ENDIAN:
    if (IS_LITTLE_ENDIAN) {
      *(field->strip_value) = field->type_byte_count > TIFF_SHORT_BYTE_COUNT
                                  ? ntohl(*(field->strip_value))
                                  : ntohs(*(field->strip_value));
    }
    break;
  case TIFF_ORDER_LITTLE_ENDIAN:
    if (IS_BIG_ENDIAN) {
      *(field->strip_value) = field->type_byte_count > TIFF_SHORT_BYTE_COUNT
                                  ? htonl(*(field->strip_value))
                                  : htons(*(field->strip_value));
    }
    break;
  }
}

internal bool read_field(const TiffField *field, TiffImage *img) {
  switch (field->tag) {
  case TIFF_PUBLIC_TAG_IMAGE_WIDTH:
    if (field->count > 1) {
      return false;
    }

    img->image_width = field->value_offset;

    break;
  case TIFF_PUBLIC_TAG_IMAGE_LENGTH:
    if (field->count > 1) {
      return false;
    }

    img->image_length = field->value_offset;

    break;
  case TIFF_PUBLIC_TAG_BITS_PER_SAMPLE:
    img->type |= field->tag;

    if (img->sample_count == INVALID_SAMPLE_COUNT) {
      img->sample_count = field->count;
    } else if (img->sample_count != field->count) {
      return false;
    }

    img->bits_per_sample = field->value_offset;

    img->bits_per_sample_offset =
        img->sample_count * field_types[field->type].byte_count > 4;

    break;
  case TIFF_PUBLIC_TAG_COMPRESSION:
    if (field->count > 1 ||
        field->value_offset != TIFF_COMPRESSION_UNCOMPRESSED) {
      return false;
    }

    img->compression = field->value_offset;

    break;
  case TIFF_PUBLIC_TAG_PHOTOMETRIC_INTERPRETATION:
    if (field->count > 1) {
      return false;
    }

    img->photometric_interpretation = field->value_offset;

    break;
  case TIFF_PUBLIC_TAG_STRIP_OFFSETS:
    img->strip_offsets_type_byte_count = field_types[field->type].byte_count;

    if (img->strip_offsets_type_byte_count == TIFF_SHORT_BYTE_COUNT) {
      img->strip_offsets.short_val = field->value_offset;
    } else if (img->strip_offsets_type_byte_count == TIFF_LONG_BYTE_COUNT) {
      img->strip_offsets.long_val = field->value_offset;
    }

    if (img->strip_count == INVALID_STRIP_COUNT) {
      img->strip_count = field->count;
    } else if (img->strip_count != field->count) {
      return false;
    }

    img->strip_offsets_offset =
        img->strip_count * img->strip_offsets_type_byte_count > 4;

    break;
  case TIFF_PUBLIC_TAG_SAMPLES_PER_PIXEL:
    img->type |= field->tag;

    if (field->count > 1) {
      return false;
    }

    img->sample_count = field->value_offset;

    break;
  case TIFF_PUBLIC_TAG_ROWS_PER_STRIP:
    if (field->count > 1) {
      return false;
    }

    img->rows_per_strip = field->value_offset;

    if (img->image_length > 0) {
      img->strip_count =
          floor((f64)(img->image_length + img->rows_per_strip - 1) /
                img->rows_per_strip);
    } else {
      img->strip_count = INVALID_STRIP_COUNT;
    }

    break;
  case TIFF_PUBLIC_TAG_STRIP_BYTE_COUNTS:
    img->strip_byte_count_type_byte_count = field_types[field->type].byte_count;

    if (img->strip_byte_count_type_byte_count == TIFF_SHORT_BYTE_COUNT) {
      img->strip_byte_counts.short_val = field->value_offset;
    } else if (img->strip_byte_count_type_byte_count == TIFF_LONG_BYTE_COUNT) {
      img->strip_byte_counts.long_val = field->value_offset;
    }

    if (img->strip_count == INVALID_STRIP_COUNT) {
      img->strip_count = field->count;
    } else if (img->strip_count != field->count) {
      return false;
    }

    img->strip_byte_counts_offset =
        img->strip_count * img->strip_byte_count_type_byte_count > 4;

    break;
  case TIFF_PUBLIC_TAG_COLOR_MAP:
    img->type |= field->tag;
    break;
  case TIFF_PUBLIC_TAG_EXTRA_SAMPLES:
    img->extra_samples_count = field->count;

    img->extra_samples = field->value_offset;

    img->extra_samples_offset =
        img->extra_samples_count * field_types[field->type].byte_count > 4;

    break;
  case TIFF_PUBLIC_TAG_PLANAR_CONFIGURATION:
    if (field->count > 1 || field->value_offset != TIFF_PLANAR_CONFIG_CHUNKY) {
      return false;
    }

    break;
  }

  return true;
}

internal bool validate_image_type(const TiffImage *img) {
  if (img->type < TIFF_IMAGE_TYPE_BILEVEL || img->type > TIFF_IMAGE_TYPE_RGB) {
    return false;
  }

  switch (img->type) {
  case TIFF_IMAGE_TYPE_BILEVEL:
  case TIFF_IMAGE_TYPE_GRAYSCALE:
    if (img->photometric_interpretation >
        TIFF_PHOTOMETRIC_INTERPRETATION_BLACK_IS_ZERO) {
      return false;
    }

    break;
  case TIFF_IMAGE_TYPE_PALETTE:
    if (img->photometric_interpretation !=
        TIFF_PHOTOMETRIC_INTERPRETATION_RGB_PALETTE) {
      return false;
    }

    break;
  case TIFF_IMAGE_TYPE_RGB:
    if (img->photometric_interpretation !=
        TIFF_PHOTOMETRIC_INTERPRETATION_RGB) {
      return false;
    }

    break;
  default:
    return false;
  }

  return true;
}

internal void fread_with_offset(FILE *fp, void *dst, u64 count, u64 offset) {
  if (!fp || !dst) {
    return;
  }

  fseek(fp, offset, SEEK_SET);

  fread(dst, count, 1, fp);
}

internal bool valid_tiff_file(const char *file) {
  u64 name_length = strlen(file);
  if (name_length < TIFF_FILENAME_MIN_LENGTH) {
    return false;
  }

  const char *ext = NULL;
  for (u32 i = name_length - 1; i >= name_length - TIFF_FILENAME_MIN_LENGTH;
       --i) {
    if (file[i] == '.') {
      ext = &(file[i]);
      break;
    }
  }

  if (!ext || !IS_TIFF_EXTENSION(ext)) {
    return false;
  }

  return true;
}