- added experimental EXIF decoding when reading JPEG files.

[imager.git] / imexif.c

#include "imexif.h"
#include <stdlib.h>
#include <float.h>

/*
=head1 NAME

imexif.c - EXIF support for Imager

=head1 SYNOPSIS

  if (i_int_decode_exif(im, app1data, app1datasize)) {
    // exif block seen
  }

=head1 DESCRIPTION

This code provides a basic EXIF data decoder.  It is intended to be
called from the JPEG reader code when an APP1 data block is found, and
will set tags in the supplied image.

=cut
*/

typedef enum tiff_type_tag {
  tt_intel = 'I',
  tt_motorola = 'M'
} tiff_type;

typedef enum {
  ift_byte = 1,
  ift_ascii = 2,
  ift_short = 3,
  ift_long = 4,
  ift_rational = 5,
  ift_sbyte = 6,
  ift_undefined = 7,
  ift_sshort = 8,
  ift_slong = 9,
  ift_srational = 10,
  ift_float = 11,
  ift_double = 12,
  ift_last = 12 /* keep the same as the highest type code */
} ifd_entry_type;

static int type_sizes[] =
  {
    0, /* not used */
    1, /* byte */
    1, /* ascii */
    2, /* short */
    4, /* long */
    8, /* rational */
    1, /* sbyte */
    1, /* undefined */
    2, /* sshort */
    4, /* slong */
    8, /* srational */
    4, /* float */
    8, /* double */
  };

typedef struct {
  int tag;
  int type;
  int count;
  int size;
  int offset;
} ifd_entry;

typedef struct {
  int tag;
  char const *name;
} tag_map;

typedef struct {
  int tag;
  char const *name;
  tag_map const *map;
  int map_count;
} tag_value_map;

#define PASTE(left, right) PASTE_(left, right)
#define PASTE_(left, right) left##right
#define QUOTE(value) #value

#define VALUE_MAP_ENTRY(name) \
  { \
    PASTE(tag_, name), \
    "exif_" QUOTE(name) "_name", \
    PASTE(name, _values), \
    ARRAY_COUNT(PASTE(name, _values)) \
  }

/* we don't process every tag */
#define tag_make 271
#define tag_model 272
#define tag_orientation 274
#define tag_x_resolution 282
#define tag_y_resolution 283
#define tag_resolution_unit 296
#define tag_copyright 33432
#define tag_software 305
#define tag_artist 315
#define tag_date_time 306
#define tag_image_description 270

#define tag_exif_ifd 34665
#define tag_gps_ifd 34853

#define resunit_none 1
#define resunit_inch 2
#define resunit_centimeter 3

/* tags from the EXIF ifd */
#define tag_exif_version 0x9000
#define tag_flashpix_version 0xA000
#define tag_color_space 0xA001
#define tag_component_configuration 0x9101
#define tag_component_bits_per_pixel 0x9102
#define tag_pixel_x_dimension 0xA002
#define tag_pixel_y_dimension 0xA003
#define tag_maker_note 0x927C
#define tag_user_comment 0x9286
#define tag_related_sound_file 0xA004
#define tag_date_time_original 0x9003
#define tag_date_time_digitized 0x9004
#define tag_sub_sec_time 0x9290
#define tag_sub_sec_time_original 0x9291
#define tag_sub_sec_time_digitized 0x9292
#define tag_image_unique_id 0xA420
#define tag_exposure_time 0x829a
#define tag_f_number 0x829D
#define tag_exposure_program 0x8822
#define tag_spectral_sensitivity 0x8824
#define tag_iso_speed_rating 0x8827
#define tag_oecf 0x8828
#define tag_shutter_speed 0x9201
#define tag_aperture 0x9202
#define tag_brightness 0x9203
#define tag_exposure_bias 0x9204
#define tag_max_aperture 0x9205
#define tag_subject_distance 0x9206
#define tag_metering_mode 0x9207
#define tag_light_source 0x9208
#define tag_flash 0x9209
#define tag_focal_length 0x920a
#define tag_subject_area 0x9214
#define tag_flash_energy 0xA20B
#define tag_spatial_frequency_response 0xA20C
#define tag_focal_plane_x_resolution 0xA20e
#define tag_focal_plane_y_resolution 0xA20F
#define tag_focal_plane_resolution_unit 0xA210
#define tag_subject_location 0xA214
#define tag_exposure_index 0xA215
#define tag_sensing_method 0xA217
#define tag_file_source 0xA300
#define tag_scene_type 0xA301
#define tag_cfa_pattern 0xA302
#define tag_custom_rendered 0xA401
#define tag_exposure_mode 0xA402
#define tag_white_balance 0xA403
#define tag_digital_zoom_ratio 0xA404
#define tag_focal_length_in_35mm_film 0xA405
#define tag_scene_capture_type 0xA406
#define tag_gain_control 0xA407
#define tag_contrast 0xA408
#define tag_saturation 0xA409
#define tag_sharpness 0xA40A
#define tag_device_setting_description 0xA40B
#define tag_subject_distance_range 0xA40C

/* don't use this on pointers */
#define ARRAY_COUNT(array) (sizeof(array)/sizeof(*array))

/* in memory tiff structure */
typedef struct {
  /* the data we use as a tiff */
  unsigned char *base;
  size_t size;

  /* intel or motorola byte order */
  tiff_type type;

  /* initial ifd offset */
  unsigned long first_ifd_offset;
  
  /* size (in entries) and data */
  int ifd_size; 
  ifd_entry *ifd;
  unsigned long next_ifd;
} imtiff;

static int tiff_init(imtiff *tiff, unsigned char *base, size_t length);
static int tiff_load_ifd(imtiff *tiff, unsigned long offset);
static void tiff_final(imtiff *tiff);
static void tiff_clear_ifd(imtiff *tiff);
static int tiff_get_bytes(imtiff *tiff, unsigned char *to, size_t offset, 
			  size_t count);
static int tiff_get_tag_double(imtiff *, int index, double *result);
static int tiff_get_tag_int(imtiff *, int index, int *result);
static unsigned tiff_get16(imtiff *, unsigned long offset);
static unsigned tiff_get32(imtiff *, unsigned long offset);
static int tiff_get16s(imtiff *, unsigned long offset);
static int tiff_get32s(imtiff *, unsigned long offset);
static double tiff_get_rat(imtiff *, unsigned long offset);
static double tiff_get_rats(imtiff *, unsigned long offset);
static void save_ifd0_tags(i_img *im, imtiff *tiff, unsigned long *exif_ifd_offset);
static void save_exif_ifd_tags(i_img *im, imtiff *tiff);
static void
copy_string_tags(i_img *im, imtiff *tiff, tag_map *map, int map_count);
static void
copy_int_tags(i_img *im, imtiff *tiff, tag_map *map, int map_count);
static void
copy_rat_tags(i_img *im, imtiff *tiff, tag_map *map, int map_count);
static void
copy_name_tags(i_img *im, imtiff *tiff, tag_value_map *map, int map_count);
static void process_maker_note(i_img *im, imtiff *tiff, unsigned long offset, size_t size);

/*
=head1 PUBLIC FUNCTIONS

These functions are available to other parts of Imager.  They aren't
intended to be called from outside of Imager.

=over

=item i_int_decode_exit

i_int_decode_exif(im, data_base, data_size);

The data from data_base for data_size bytes will be scanned for EXIF
data.

Any data found will be used to set tags in the supplied image.

The intent is that invalid EXIF data will simply fail to set tags, and
write to the log.  In no case should this code exit when supplied
invalid data.

Returns true if an Exif header was seen.

*/

int
i_int_decode_exif(i_img *im, unsigned char *data, size_t length) {
  imtiff tiff;
  unsigned long exif_ifd_offset = 0;
  unsigned long ifd1_offset;
  /* basic checks - must start with "Exif\0\0" */

  if (length < 6 || memcmp(data, "Exif\0\0", 6) != 0) {
    return 0;
  }

  data += 6;
  length -= 6;

  if (!tiff_init(&tiff, data, length)) {
    mm_log((2, "Exif header found, but no valid TIFF header\n"));
    return 1;
  }
  if (!tiff_load_ifd(&tiff, tiff.first_ifd_offset)) {
    mm_log((2, "Exif header found, but could not load IFD 0\n"));
    tiff_final(&tiff);
    return 1;
  }

  save_ifd0_tags(im, &tiff, &exif_ifd_offset);

  if (exif_ifd_offset) {
    if (tiff_load_ifd(&tiff, exif_ifd_offset)) {
      save_exif_ifd_tags(im, &tiff);
    }
    else {
      mm_log((2, "Could not load Exif IFD\n"));
    }
  }

  tiff_final(&tiff);

  return 1;
}

/*

=back

=head1 INTERNAL FUNCTIONS

=head2 EXIF Processing 

=over

=item save_ifd0_tags

save_ifd0_tags(im, tiff, &exif_ifd_offset)

Scans the currently loaded IFD for tags expected in IFD0 and sets them
in the image.

Sets *exif_ifd_offset to the offset of the EXIF IFD if found.

=cut

*/

static tag_map ifd0_string_tags[] =
  {
    tag_make, "exif_make",
    tag_model, "exif_model",
    tag_copyright, "exif_copyright",
    tag_software, "exif_software",
    tag_artist, "exif_artist",
    tag_date_time, "exif_date_time",
    tag_image_description, "exif_image_description",
  };

static const int ifd0_string_tag_count = ARRAY_COUNT(ifd0_string_tags);

static tag_map ifd0_int_tags[] =
  {
    { tag_orientation, "exif_orientation", },
    { tag_resolution_unit, "exif_resolution_unit" },
  };

static const int ifd0_int_tag_count = ARRAY_COUNT(ifd0_int_tags);

static tag_map ifd0_rat_tags[] =
  {
    { tag_x_resolution, "exif_x_resolution" },
    { tag_y_resolution, "exif_y_resolution" },
  };

static tag_map resolution_unit_values[] =
  {
    { 1, "none" },
    { 2, "inches" },
    { 3, "centimeters" },
  };

static tag_value_map ifd0_values[] =
  {
    VALUE_MAP_ENTRY(resolution_unit),
  };

static void
save_ifd0_tags(i_img *im, imtiff *tiff, unsigned long *exif_ifd_offset) {
  int i, tag_index;
  int work;
  ifd_entry *entry;

  for (tag_index = 0, entry = tiff->ifd; 
       tag_index < tiff->ifd_size; ++tag_index, ++entry) {
    switch (entry->tag) {
    case tag_exif_ifd:
      if (tiff_get_tag_int(tiff, tag_index, &work))
	*exif_ifd_offset = work;
      break;
    }
  }

  copy_string_tags(im, tiff, ifd0_string_tags, ifd0_string_tag_count);
  copy_int_tags(im, tiff, ifd0_int_tags, ifd0_int_tag_count);
  copy_rat_tags(im, tiff, ifd0_rat_tags, ARRAY_COUNT(ifd0_rat_tags));
  copy_name_tags(im, tiff, ifd0_values, ARRAY_COUNT(ifd0_values));
}

/*
=item save_exif_ifd_tags

save_exif_ifd_tags(im, tiff)

Scans the currently loaded IFD for the tags expected in the EXIF IFD
and sets them as tags in the image.

=cut

*/

static tag_map exif_ifd_string_tags[] =
  {
    { tag_exif_version, "exif_version", },
    { tag_flashpix_version, "exif_flashpix_version", },
    { tag_related_sound_file, "exif_related_sound_file", },
    { tag_date_time_original, "exif_date_time_original", },
    { tag_date_time_digitized, "exif_date_time_digitized", },
    { tag_sub_sec_time, "exif_sub_sec_time" },
    { tag_sub_sec_time_original, "exif_sub_sec_time_original" },
    { tag_sub_sec_time_digitized, "exif_sub_sec_time_digitized" },
    { tag_image_unique_id, "exif_image_unique_id" },
    { tag_spectral_sensitivity, "exif_spectral_sensitivity" },
  };

static const int exif_ifd_string_tag_count = ARRAY_COUNT(exif_ifd_string_tags);

static tag_map exif_ifd_int_tags[] =
  {
    { tag_color_space, "exif_color_space" },
    { tag_exposure_program, "exif_exposure_program" },
    { tag_iso_speed_rating, "exif_iso_speed_rating" },
    { tag_metering_mode, "exif_metering_mode" },
    { tag_light_source, "exif_light_source" },
    { tag_flash, "exif_flash" },
    { tag_focal_plane_resolution_unit, "exif_focal_plane_resolution_unit" },
    { tag_subject_location, "exif_subject_location" },
    { tag_sensing_method, "exif_sensing_method" },
    { tag_custom_rendered, "exif_custom_rendered" },
    { tag_exposure_mode, "exif_exposure_mode" },
    { tag_white_balance, "exif_white_balance" },
    { tag_focal_length_in_35mm_film, "exif_focal_length_in_35mm_film" },
    { tag_scene_capture_type, "exif_scene_capture_type" },
    { tag_contrast, "exif_contrast" },
    { tag_saturation, "exif_saturation" },
    { tag_sharpness, "exif_sharpness" },
    { tag_subject_distance_range, "exif_subject_distance_range" },
  };


static const int exif_ifd_int_tag_count = ARRAY_COUNT(exif_ifd_int_tags);

static tag_map exif_ifd_rat_tags[] =
  {
    { tag_exposure_time, "exif_exposure_time" },
    { tag_f_number, "exif_f_number" },
    { tag_shutter_speed, "exif_shutter_speed" },
    { tag_aperture, "exif_aperture" },
    { tag_brightness, "exif_brightness" },
    { tag_exposure_bias, "exif_exposure_bias" },
    { tag_max_aperture, "exif_max_aperture" },
    { tag_subject_distance, "exif_subject_distance" },
    { tag_focal_length, "exif_focal_length" },
    { tag_flash_energy, "exif_flash_energy" },
    { tag_focal_plane_x_resolution, "exif_focal_plane_x_resolution" },
    { tag_focal_plane_y_resolution, "exif_focal_plane_y_resolution" },
    { tag_exposure_index, "exif_exposure_index" },
    { tag_digital_zoom_ratio, "exif_digital_zoom_ratio" },
    { tag_gain_control, "exif_gain_control" },
  };

static const int exif_ifd_rat_tag_count = ARRAY_COUNT(exif_ifd_rat_tags);

static tag_map exposure_mode_values[] =
  {
    { 0, "Auto exposure" },
    { 1, "Manual exposure" },
    { 2, "Auto bracket" },
  };
static tag_map color_space_values[] =
  {
    { 1, "sRGB" },
    { 0xFFFF, "Uncalibrated" },
  };

static tag_map exposure_program_values[] =
  {
    { 0, "Not defined" },
    { 1, "Manual" },
    { 2, "Normal program" },
    { 3, "Aperture priority" },
    { 4, "Shutter priority" },
    { 5, "Creative program" },
    { 6, "Action program" },
    { 7, "Portrait mode" },
    { 8, "Landscape mode" },
  };

static tag_map metering_mode_values[] =
  {
    { 0, "unknown" },
    { 1, "Average" },
    { 2, "CenterWeightedAverage" },
    { 3, "Spot" },
    { 4, "MultiSpot" },
    { 5, "Pattern" },
    { 6, "Partial" },
    { 255, "other" },
  };

static tag_map light_source_values[] =
  {
    { 0, "unknown" },
    { 1, "Daylight" },
    { 2, "Fluorescent" },
    { 3, "Tungsten (incandescent light)" },
    { 4, "Flash" },
    { 9, "Fine weather" },
    { 10, "Cloudy weather" },
    { 11, "Shade" },