luaexif

This is a Lua binding for libexif. Compatible with Lua 5.1 or later.

Install

$ luarocks make LIBEXIF_DIR=/usr/local

Or, manually with Makefile:

$ make LUA=/usr/local LIBEXIF=/usr LDFLAGS=-shared
$ cp exif.so /path/to/module/dir/

Manual

The exif module:

• exif = require "exif" Loads the module and set it to a variable. Note that the call to require does not set a global variable.
• exif.new() Allocates a new data and returns it.
• exif.loadfile(filename) Loads the file specified by filename. Returns a data.
• exif.loadbuffer(buffer) Loads the buffer given by buffer. Returns a data.

Data types:

• data --- the entire EXIF data found in an image.
  • mnotedata = data.mnotedata Returns the MakerNote data.
  • data:fix()
  • data:loadbuffer(buffer)
  • content = data:ifd(ifd) ifd is one of "0","1","EXIF","GPS","Interoperability". Returns an IFD.
  • data:ifds() Returns a integer-indexed table that contains all IFDs.
• content --- all EXIF tags found in a single IFD.
  • content:fix()
  • content.ifd Returns one of "0","1","EXIF","GPS","Interoperability".
  • entry = content:entry(tag) Returns an EXIF tag.
  • content:entries() Returns a table that contains all EXIF tags.
  • content.parent
• entry --- one EXIF tag
  • entry:fix()
  • entry.tag Tag name as a string.
  • entry.value Returns a localized textual representation of the value.
  • entry.components
  • entry.format Returns a textual representation of the data type.
  • entry.rawdata
  • entry.parent Returns the content object to which entry belongs.
  • entry.data Same as entry[1]
  • entry[n] (n is an integer between 1 and entry.components)
  • tostring(entry) Same as entry.value.
• mnotedata --- all data found in MakerNote tag.
  • #mnotedata
  • mnotedata[n] n is an integer between 1 and #mnotedata.
• rational --- a rational number, possibly returned by entry.data or entry[n]
  • rational.numerator The numerator as an integer.
  • rational.denominator The denominator as an integer.
  • rational.value The ratio as a Lua number.
  • tostring(rational) Same as rational.numerator .. "/" .. rational.denominator.

Example

local exif = require "exif"
local data = exif.loadfile("mypicture.jpg") -- Load the EXIF data from "mypicture.jpg"
print(data:ifd("0"):entry("DateTime")) --> "2014:10:25 12:55:22"
local ExposureTime = data:ifd("EXIF"):entry("ExposureTime")
print(ExposureTime) --> "1/125 sec."
print(ExposureTime.format) --> "Rational"
print(ExposureTime.data) --> "1/125"
print(ExposureTime.data.value) --> "0.008"

Note that requiring "exif" module doesn't set a global variable with the module name. You can assign the module (result of require) to a local variable, as in the example above.

Links

• Lua
• libexif