www.devco.net by r.i.pienaar

Net::MovableType and Image::ExifTool

Posts for my photoblog are structured in a specific way. I put the image name in the entry body and the text in the extended entry. As long as I stick to that format my templates will automatically put in the right thumbnails, full size images etc.

While this is pretty simple to keep in mind and I have been doing it manually I wanted to automate things a bit. I also wanted to include some EXIF info for each image which Movable Type could not do on its own.

The solution was to write a simple blogging client in perl, read on for some details.

First off, lets cover the EXIF extraction, I found a excellent module in the FreeBSD ports system called Image::ExifTool. From its description:

ExifTool provides an extensible set of perl modules to read and write
meta information in image files. It reads EXIF, GPS, IPTC, XMP,
GeoTIFF, ICC Profile and Photoshop IRB meta information from JPEG,
TIFF, GIF, THM, CRW (Canon RAW), CR2 (Canon 1D Mk II RAW), MRW (Minolta
RAW), NEF (Nikon Electronic image Format), PEF (Pentax RAW), ORF
(Olympus RAW Format) and DNG (Digital Negative) images, as well as the
maker notes of many digital cameras by various manufacturers including
Canon, Casio, FujiFilm, Minolta/Konica-Minolta, Nikon, Olympus/Epson,
Panasonic/Leica, Pentax/Asahi, Sanyo and Sigma/Foveon. It writes EXIF,
GPS, IPTC, XMP and MakerNotes information to JPEG, TIFF, GIF, THM, CR2,
NEF, PEF and DNG files.

Using it is trivial, and you can read all the details at its CPAN Page. For me it was as simple as this:

my $exifTool = new Image::ExifTool;$exifInfo = $exifTool->ImageInfo("$photodir/$image");

$tagDescription = $exifTool->GetDescription($tag);

%tagValue = $exifTool->GetValue($tag);

Really simple, to see for yourself what information this will find
in a image you can run the included 'exiftool' script, here is some
sample output:

---- ExifTool ----
ExifTool Version Number : 3.72
---- File ----
File Name : 30012005.jpg
File Size : 67KB
File Type : JPG
Image Width : 366
Image Height : 550
---- EXIF ----
Software : Adobe Photoshop CS Windows
Flash : No Flash
Exif Image Width : 366
Exif Image Length : 550
Compression : JPEG (old-style)
Thumbnail Offset : 586
Thumbnail Length : 6137
---- IPTC ----
Application Record Version : 2
---- Photoshop ----
Photoshop Thumbnail : (Binary data 6137 bytes, use -b option to extract)
---- XMP ----
Version : 2.2
Raw File Name : DSC_4995.NEF
White Balance : As Shot
Exposure : +0.85
Shadows : 5
Brightness : 50
Contrast : +25
Saturation : 0
Sharpness : 25
Luminance Smoothing : 0
Color Noise Reduction : 25
Chromatic Aberration R : 0
Chromatic Aberration B : 0
Vignette Amount : 0
Shadow Tint : 0
Red Hue : 0
Red Saturation : 0
Green Hue : 0
Green Saturation : 0
Blue Hue : 0
Blue Saturation : 0
Tv(Shutter Speed) : 1/500
Shutter Speed Value : 1/500
Av(Aperture Value) : 5.6
Aperture Value : 5.6
Exposure Program : Program AE
Shooting Date/Time : 2005:01:23 13:58:27
Exposure Compensation : -0.33
Max Aperture Value : 5.7
Metering Mode : Multi-segment
Focal Length : 125.0mm
Focal Length In 35mm Format : 187
Color Space : Unknown (4294967295)
ISO Speed : 200
Flash Fired : False
Flash Return : No return detection
Flash Mode : Unknown (0)
Flash Function : False
Flash Red Eye Mode : False
Lens : 18.0-125.0 mm f/3.3-5.6
Make : NIKON CORPORATION
Camera Model Name : NIKON D70
Orientation : Horizontal (normal)
X Resolution : 300
Y Resolution : 300
Resolution Unit : inches
Creator Tool : Adobe Photoshop CS Windows
Date/Time Of Last Modification : 2005:01:23 17:21:22
Date/Time Of Digitization : 2005:01:23 17:21:22
Metadata Date : 2005:01:23 17:21:22
Derived From Instance ID : uuid:121a03ec-6d63-11d9-bfa3-cf79758759c4
Derived From Document ID : adobe:docid:photoshop:121a03eb-6d63-11d9-bfa3-cf79758759c4
Document ID : adobe:docid:photoshop:121a03ef-6d63-11d9-bfa3-cf79758759c4
Format : image/jpeg
---- Composite ----
Av(Aperture Value) : 5.6
Image Size : 366x550
Scale Factor To 35mm Equivalent : 1.5
Tv(Shutter Speed) : 1/500
Thumbnail Image : (Binary data 6137 bytes, use -b option to extract)
Focal Length : 125.0mm (35mm equivalent: 187.0mm)

This is very impressive, you can see multiple sets of data, example
is the Exposure, I shot it at -0.33 in the camera then bumped it to
+0.85 in Photoshop CS RAW Plugin.

Now that I have a good way to extract meta data from my images the next step was to do the blog posting, this was trivial using Net::MovableType, below is a quick code snippet, read all about it at CPAN

use Net::MovableType;

my $mt = new Net::MovableType('http://your.com/rsd.xml');
$mt->username('user');

$mt->password('secret');

$entry = {
   title => "Hello World from Net::MovableType",
   description => "Look ma, no hands!"
};

$postID = $mt->newPost($entry);
$mt->publishPost($postID);

Very simple, it has many other functions, you can read, edit,
categorise etc, all the stuff you can do from the standard Movable Type
API.