Ruby EXIF reader written in C extension.

Installation

$ gem install exif

Please make sure you have installed libexif first.

Usage

data = Exif::Data.new('sample.jpg')
data.model         # => "NIKON D600"
data.image_width   # => 4000
data.gps_longitude # => 121.51246
data.date_time     # => 2013-12-08 21:14:11 0800

# get all entries in an IFD
data[0]                 # => {image_width: 4000, image_length: 2670, ...}
data[1]                 # => {x_resolution: "72", y_resolution: "72", ...}
data[:exif]             # => exposure_time: "1/125 sec.", f_number: "f/8.0"}
data[:gps]              # => {gps_version_id: "2.2.0.0", gps_latitude_ref: "N", ...}
data[:interoperability] # => {...}
data.to_h               # => {0 => {...}, 1 => {...}, :exif => {...}}

How fast?

There is another excellent work called exifr made by @remvee. That's pure Ruby while this one is C extension. If you program JRuby, you may want to choose exifr, otherwise you can try this gem for speed purpose, it's about 8 times faster. A small benchmark shows below:

require 'benchmark'
require 'exif'
require 'exifr'
N = 500
FILE_PATH = 'sample.jpg'
Benchmark.bmbm do |x|
  x.report '[exifr] init' do
    N.times{ EXIFR::JPEG.new(FILE_PATH).width }
  end
  x.report '[exif]  init' do
    N.times{ Exif::Data.new(FILE_PATH).image_width }
  end
end

$ ruby benchmark/benchmark.rb
Rehearsal ------------------------------------------------
[exifr] init   0.810000   0.020000   0.830000 (  0.840701)
[exif]  init   0.090000   0.010000   0.100000 (  0.099700)
--------------------------------------- total: 0.930000sec

                   user     system      total        real
[exifr] init   0.810000   0.020000   0.830000 (  0.830644)
[exif]  init   0.090000   0.010000   0.100000 (  0.095148)

Tag Rreference

• aperture_value
• artist
• battery_level
• bits_per_sample
• brightness_value
• cfa_pattern
• cfa_repeat_pattern_dim
• color_space
• components_configuration
• compressed_bits_per_pixel
• compression
• contrast
• copyright
• custom_rendered
• date_time
• date_time_digitized
• date_time_original
• device_setting_description
• digital_zoom_ratio
• document_name
• exif_ifd_pointer
• exif_version
• exposure_bias_value
• exposure_index
• exposure_mode
• exposure_program
• exposure_time
• file_source
• fill_order
• flash
• flash_energy
• flash_pix_version
• fnumber
• focal_length
• focal_length_in_35mm_film
• focal_plane_resolution_unit
• focal_plane_x_resolution
• focal_plane_y_resolution
• gain_control
• gamma
• gps_altitude
• gps_altitude_ref
• gps_area_information
• gps_date_stamp
• gps_dest_bearing
• gps_dest_bearing_ref
• gps_dest_distance
• gps_dest_distance_ref
• gps_dest_latitude
• gps_dest_latitude_ref
• gps_dest_longitude
• gps_dest_longitude_ref
• gps_differential
• gps_dop
• gps_img_direction
• gps_img_direction_ref
• gps_info_ifd_pointer
• gps_latitude
• gps_latitude_ref
• gps_longitude
• gps_longitude_ref
• gps_map_datum
• gps_measure_mode
• gps_processing_method
• gps_satellites
• gps_speed
• gps_speed_ref
• gps_status
• gps_time_stamp
• gps_track
• gps_track_ref
• gps_version_id
• image_description
• image_length
• image_resources
• image_unique_id
• image_width
• inter_color_profile
• interoperability_ifd_pointer
• interoperability_index
• interoperability_version
• iptc_naa
• iso_speed_ratings
• jpeg_interchange_format
• jpeg_interchange_format_length
• jpeg_proc
• light_source
• make
• maker_note
• max_aperture_value
• metering_mode
• model
• new_cfa_pattern
• new_subfile_type
• oecf
• orientation
• padding
• photometric_interpretation
• pixel_x_dimension
• pixel_y_dimension
• planar_configuration
• primary_chromaticities
• print_image_matching
• reference_black_white
• related_image_file_format
• related_image_length
• related_image_width
• related_sound_file
• resolution_unit
• rows_per_strip
• samples_per_pixel
• saturation
• scene_capture_type
• scene_type
• sensing_method
• sharpness
• shutter_speed_value
• software
• spatial_frequency_response
• spectral_sensitivity
• strip_byte_counts
• strip_offsets
• sub_ifds
• sub_sec_time
• sub_sec_time_digitized
• sub_sec_time_original
• subject_area
• subject_distance
• subject_distance_range
• subject_location
• tiff_ep_standard_id
• time_zone_offset
• transfer_function
• transfer_range
• user_comment
• white_balance
• white_point
• x_resolution
• xml_packet
• xp_author
• xp_comment
• xp_keywords
• xp_subject
• xp_title
• y_resolution
• ycbcr_coefficients
• ycbcr_positioning
• ycbcr_sub_sampling

TODO

1. Support reading from String.