Photo Tools

1
Photo Tools Perl scripts for digital photography
Jon Allen
http//perl.jonallen.info - jj_at_jonallen.info
2
Organisation

• Digital photography can create lots of files
• Camera filenames are usually meaningless
• Manual file renaming
• Very time consuming
• Doesn't scale well (100s of folders, most called
  "cats")
• Use management software
• Many products import files into their own library
  format
• Difficult to use other tools or to change systems

3
Ideal solution

• Standard directory structure, based on date

4
ImageExifTool

• Cameras store image metadata as "EXIF tags"
• Timestamp, focal length, shutter speed, aperture,
  etc.
• ImageExifTool provides an API and command-line
  utility to access and modify this data
• See http//search.cpan.org/dist/Image-ExifTool

use ImageExifTool my exif
ImageExifTool-gtnew() my tags
exif-gtImageInfo(filename) say "Shutter speed
was tags-gtShutterSpeed"
5
Getting the timestamp

• We need the timestamp as a TimePiece object
• TimePiece is a core module from Perl 5.10.0
• See http//search.cpan.org/dist/Time-Piece

sub exif_timestamp my filename shift my
format 'YmdHMS' my exif
ImageExifTool-gtnew() my tags
exif-gtImageInfo(filename,
DateFormatgtformat) return
TimePiece-gtstrptime(tags-gtDateTimeOriginal,
format)
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Change time zone

• Who remembers to update the clock on their camera
  when going abroad?
• Using TimePiece objects this is an easy fix
• TimeSeconds exports various useful constants

use TimePiece use TimeSeconds my time
exif_timestamp(filename) my offset -8 8
hours behind UK time offset ONE_HOUR
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Creating the new filenames

• Use a template gives flexibility
• TimePiece uses POSIX format specification
• Oracle date formats are more "human-friendly"
• http//search.cpan.org/dist/Convert-NLS_DATE_FORMA
  T

use ConvertNLS_DATE_FORMAT qw/oracle2posix/ my
template '?YYYY/MM/DD/YYYY-MM-DD_HH24-MI-SS'
?my target time-gtstrftime(oracle2posix(temp
late)) Target filename is in the format
2008/05/13/2008-05-13_17-23-00
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Finishing up

• What next
• Prepend destination directory to target filename
• Check full path already exists (and if not,
  create it)
• Does the file already exist? If so, add a
  sequence number (some cameras can take multiple
  images per second)
• Copy the file!

copy_rename( source gt filename,
destination gt destination_dir, template gt
template, offset gt offset, )
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Finding the source files
use FileFind Perl core module my
find_options find_optionsno_chdir
1 find_optionswanted sub if
(/\.(jpgjpejpegtiftiff)/i)
copy_rename( source gt
FileFindname, destination gt
destination_dir, template gt
template, offset gt offset, )
find(\find_options, source_directory)
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More uses for EXIF tags

• Keywords can be embedded in images
• Spotlight (OS X), Beagle (Linux), and Windows
  search engines can read EXIF keywords

my keywords 'Dubai', 'Sunset' my exif
ImageExifTool-gtnew() exif-gtSetNewValuesFrom
File(filename) exif-gtSetNewValue('Keywords',k
eywords) exif-gtSetNewValue('XPKeywords',join ',
',_at_keywords) exif-gtWriteInfo(filename)
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Searching by keyword
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copyphotos.pl

• http//perl.jonallen.info/projects/copyphotos

./copyphotos.pl --offset-1 --template
"YYYY/MM_Mon/DD_Day/HH24-MI-SS"
--keyword "Dubai" -keyword "Sunset"
source/ photos/ Copying
source/a.jpg to photos/2004/01_Jan/25_Sunday/17-29
-05.jpg ... OK Copying source/b.JPG to
photos/2006/11_Nov/18_Saturday/16-55-13.JPG ...
OK Copying source/c.JPG to photos/2006/11_Nov/18_S
aturday/16-58-06.JPG ... OK Copying source/d.JPG
to photos/2006/01_Jan/28_Saturday/12-03-47.JPG
... OK
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Future enhancements

• Automatic keyword generation
• Camera knows when a picture was taken
• A GPS tracker knows where you were
• Your calendar (or phone) knows what you were
  doing
• Correlate these together into a list of keywords

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Camera aspect ratios

• Cameras typically use one of two aspect ratios
• 32 (11.5)
• Based on 35mm film format
• Canon, Nikon, Pentax, Sony DSLRs
• 43 (11.33)
• Olympus, Panasonic, Leica DSLRs
• Most compact digital cameras

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Printing the aspect ratio problem

• There are many "standard" paper sizes in use
• 6x4 (11.5)
• 7x5 (11.4)
• 10x8 (11.25)
• A4 (11.41)
• If the paper aspect ratio does not match your
  camera, then part of the image will be cropped
• Note that "full-bleed" printing will slightly
  crop all sides of an image, even if the aspect
  ratios match

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Headless chickens

• A standard 7x5 print does not match either of the
  camera formats particularly well

32 format 7 lost (½")
43 format 5 lost (¼")
7x5
17
Removing the need to crop

• Cropping can be avoided by adding a border
• Makes the image aspect ratio equal to the paper

7x5 paper 43 image No cropping!
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Find the original sizes

• How big is the image?
• How big is the paper?

use ImageSize my (width,height)
imgsize(filename)
use PaperSpecs my paper_size
'A4' PaperSpecs-gtunits('in') my page
PaperSpecs-gtfind(codegtpaper_size)
or die("Invalid paper size\n") my width
page-gtsheet_width my height
page-gtsheet_height
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Compare the aspect ratios

• Compare based on the longest sides
• With a 43 image and 7x5 paper
• paper_aspect 1.4, image_aspect 1.33

use ListUtil qw/max min/ my paper_longside
max(paper_width,paper_height) my
paper_shortside min(paper_width,paper_height)
my paper_aspect paper_longside /
paper_shortside my image_longside
max(image_width,image_height) my
image_shortside min(image_width,image_height)
my image_aspect image_longside /
image_shortside
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Which way to adjust?

• If paper_aspect gt image_aspect, we need to add
  borders to the long side of the image
• If image_aspect gt paper_aspect, we need to add
  borders to the short side of the image

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Work out the new sizes

• Equal border on each side to centre the image

my target_longside image_longside my
target_shortside image_shortside my
(border_longside,border_shortside) (0,0) if
(paper_aspect gt image_aspect)
target_longside image_shortside
paper_aspect border_longside
(target_longside
image_longside) / 2 else
target_shortside image_longside /
paper_aspect border_shortside
(target_shortside -
image_shortside) / 2
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ImageMagick

• Open source image manipulation library
• Supports over 100 image formats
• Very high quality resizing algorithms
• Command-line tools and APIs for Perl, C, PHP,
  .NET, etc
• See http//www.imagemagick.org

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ImageMagick

• Open source image manipulation library
• Supports over 100 image formats
• Very high quality resizing algorithms
• Command-line tools and APIs for Perl, C, PHP,
  .NET, etc
• See http//www.imagemagick.org
• However
• Can be difficult to build
• Even harder to package!
• Remember Elaine's Law
• "Just make it easy to install, stupid!"

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ImageMagick

• Open source image manipulation library
• Supports over 100 image formats
• Very high quality resizing algorithms
• Command-line tools and APIs for Perl, C, PHP,
  .NET, etc
• See http//www.imagemagick.org
• However
• Can be difficult to build
• Even harder to package!
• Remember Elaine's Law
• "Just make it easy to install, stupid!"

FAIL
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Imager

• Self-contained Perl module
• http//search.cpan.org/dist/Imager
• Installs from CPAN shell
• Requires file format libraries (libjpeg, libtiff
  etc)
• Works with PAR!
• Include libraries with pp ?-l ./libjpeg.62.dylib
• Disadvantages
• Fewer facilities than ImageMagick
• Strips image metadata (EXIF)

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Adding a border with Imager
use Imager my source Imager-gtnew-gtread(filegt
source_filename) my dest Imager-gtnew(
xsize gt source-gtgetwidth() 2
border_width, ysize gt source-gtgetheight()
2 border_height, bits gt
source-gtbits, channels gt source-gtgetchannels
) dest-gtbox(filledgt1, colorgt'white') dest-gt
paste(imggtsource,
topgtborder_height, leftgtborder_width) dest-
gtwrite(filegttarget_filename,jpegqualitygt100)
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What happened to the colours?

• Unfortunately, Imager strips metadata
• This includes EXIF tags and the ICC colour
  profile
• ImageExifTool can copy the EXIF tags and ICC
  profile back from the original file

use ImageExifTool ?my exif
ImageExifTool-gtnew() ?exif-gtSetNewValuesFromF
ile(source_filename) ?exif-gt?WriteInfo(target_
filename)
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Image aspect ratio changed

• We now have an image with the correct aspect
  ratio, padded with borders on two sides
• For a full-bleed print, we need a border around
  all four sides of the image

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The problem with borders

• Applying an even border to a rectangular image
  will affect its aspect ratio
• A 7x5 image (1.4 aspect) with an even ½" border
  would become an 8x6 image (1.33 aspect)
• To keep the correct aspect ratio, we need to add
  a ½" border to the short side and a (½ 1.4)"
  border to the long side
• How do we work this out in pixels?

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Calculating the border sizes

• 7x5 paper with ½" border
• Short side of image will be (5"-½"-½") 4"
• Image resolution 500px / 4" 125dpi
• Short side border ½" 125dpi 62.5px
• Long side border 62.5 1.4 87.5px

500px
700px
625px
875px
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photofit.pl

• http//perl.jonallen.info/projects/photofit

./photofit.pl --paper-size7x5 --border0.5in
sunset.jpg
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Fin!
Thank you for listening!
Any questions? http//perl.jonallen.info/talks