A Ruby EXIF reader written in C.

Installation

$ gem install exif

Please make sure you have installed libexif:

$ brew install libexif             # Homebrew
$ sudo apt-get install libexif-dev # APT
$ sudo yum install libexif-devel   # CentOS

Usage

data = Exif::Data.new(IO.read('sample.jpg'))   # load from string
data = Exif::Data.new("Exif\x00\x00II...")     # load raw exif data
data = Exif::Data.new(File.open('sample.jpg')) # load from file
data.model         # => "NIKON D600"
data.image_width   # => 4000
data.gps_longitude # => [(121/1), (76869/2500), (0/1)]
data.date_time     # => "2013:12:08 21:14:11"

# get all entries in an IFD
data[:ifd0]             # => {image_width: 4000, image_length: 2670, ...}
data[:ifd1]             # => {x_resolution: (72/1), y_resolution: (72/1), ...}
data[:exif]             # => exposure_time: (1/125), fnumber: (8/1)}
data[:gps]              # => {gps_version_id: [2, 2, 0, 0], gps_latitude_ref: "N", ...}
data[:interoperability] # => {...}
data.to_h               # => {:ifd0 => {...}, :ifd1 => {...}, :exif => {...}}
data.ifds == data.to_h  # => true

ifd0 takes precedence over ifd1, since ifd0 and ifd1 share the same domain of tags, sometimes the same tag can be both used inside them, in this case, calling top-level API like Exif::Data#image_width will return the value of ifd0.

Typecasting

Tag Type	Ruby Class
ASCII	String
BYTE	Integer
DOUBLE	Flat
FLOAT	Float
LONG	Integer
RATIONAL	Rational
SHORT	Integer
UNDEFINED	String

How fast?

It's hundreds of times faster than mini_exiftool or exiftool and several times faster than exifr.

There are similar excellent gems like exifr, mini_exiftool and exiftool built in pure Ruby while this one is a C extension.

If you are using JRuby you might want to give exifr, exiftool or mini_exiftool a look, the latter two are commandline wrappers for ExifTool by Phil Harvey and support many file formats. The exiftool gem can process multiple files at once while mini_exiftool can modify or copy EXIF data.

Benchmark

You can find all benchmark files in /benchmark:

Read a single tag from 100 files.

$ ruby benchmark/load_file.rb
Rehearsal ---------------------------------------------------------
mini_exiftool (2.9.0)   0.240000   0.110000  22.830000 ( 23.275885)
exiftool (1.2.0)        0.480000   0.130000  22.870000 ( 23.311755)
exifr (1.3.2)           0.120000   0.010000   0.130000 (  0.139821)
exif (49b6835)          0.020000   0.000000   0.020000 (  0.019927)
----------------------------------------------- total: 45.850000sec

                            user     system      total        real
mini_exiftool (2.9.0)   0.240000   0.120000  22.830000 ( 23.267355)
exiftool (1.2.0)        0.490000   0.130000  23.190000 ( 23.678799)
exifr (1.3.2)           0.120000   0.010000   0.130000 (  0.134572)
exif (49b6835)          0.020000   0.000000   0.020000 (  0.018419)
-----------------------------------------
1263 times faster than mini_exiftool (2.9.0)
1286 times faster than exiftool (1.2.0)
7 times faster than exifr (1.3.2)

Read many tags from the same file 1000 times.

$ ruby benchmark/read_tag.rb
Rehearsal ---------------------------------------------------------
mini_exiftool (2.9.0)   0.390000   0.000000   0.390000 (  0.404067)
exiftool (1.2.0)        0.030000   0.000000   0.030000 (  0.027073)
exifr (1.3.2)           1.220000   0.020000   1.240000 (  1.268672)
exif (49b6835)          0.010000   0.000000   0.010000 (  0.006862)
------------------------------------------------ total: 1.670000sec

                            user     system      total        real
mini_exiftool (2.9.0)   0.410000   0.010000   0.420000 (  0.412627)
exiftool (1.2.0)        0.030000   0.000000   0.030000 (  0.028518)
exifr (1.3.2)           1.180000   0.010000   1.190000 (  1.203806)
exif (49b6835)          0.010000   0.000000   0.010000 (  0.006925)
-----------------------------------------
60 times faster than mini_exiftool (2.9.0)
4 times faster than exiftool (1.2.0)
174 times faster than exifr (1.3.2)

Contribution

Please follow AngularJS git commit message conventions.

TODO

Create, update and delete tags.

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tonytonyjan / exif

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