FOSS, 24th April 2014 Digital Image Management Roger Hurley

1. Introduction I currently use three open source photography applications: digiKam for organising my image files; GIMP as a pixel editor; and RawTherapee as a RAW processor. There is a degree of overlap in functionality between these packages but, since this presentation is about organising digital photographs, this document concentrates on the image management capabilities of digiKam. In the old days there were two approaches: The Shoe Box ­ Put all the photographs into an old shoe box and look at them once a year; The Librarian ­ Carefully write details on the back of each photograph and file them away in albums; look at them occasionally. Having annotated the photos, they could be sorted by the date they were taken and/or their subject matter, depending on how much work you wanted to do. With the advent of digital photography, we gained the ability to store our images in a logical directory/sub­directory structure, creating virtual albums. These could be organised by date, event, subject matter, etc., or combinations of these, as indicated below:

This is all very well, but it doesn't give us much more than the old Librarian approach. However, digital cameras also save information about the images; this is known as metadata and most of it is saved as an exif file within the image file (.jpg, .tiff, .raw, etc.). An ex if file can contain a great deal of information about the image: make & model of camera; date & time when the image was created; camera settings ­ aperture, shutter speed, sensitivity (iso), focal length, white balance; flash settings, image resolution, etc.; file size and format; and so on. Most image editing programs are able to interrogate the metadata of a set of images, to provide powerful search tools. Editing programs also allow the user to add more information to an image, such as star, colour and flag ratings and user­defined tags. Together with the metadata, we now have the tools to sort our images regardless of how they are arranged on our digital storage media. 2. Overview of digiKam digiKam is described in the manual as follows: "digiKam is a digital photo management application for the importing, organizing and editing of digital photographs. It enables you to manage large numbers of images in "albums" and to organise them for easy retrieval using tags (keywords), captions, collections, dates, geolocation and searches. It has many features for viewing, organizing, processing and sharing images. While digiKam remains easy to use, it provides professional level features by the dozen. It is fully 16 bit enabled including all available plugins, supports RAW format conversion through libraw, DNG export and ICC color management work flow." I've been using digiKam primarily for organising my digital images, so am not familiar with the importing and editing functions but, with respect to organising, digiKam's key features are that it can: • Display images contained in the sub-directories you've defined as digiKam "albums", either as groups of thumbnails or single previews; • Recognise most common image formats, including RAW files (some viewers cannot open RAW files); • Apply markers - titles, descriptions, tags (keywords) and flags (flag, star and colour ratings) - to individual images or groups of images, and to search on these markers; • Search on numerous other data items stored in the EXIF files; • Identify duplicates and near-duplicates of images so you can delete unwanted files; • Identify faces in images, with the ability to add names for future searching; • Group (or "stack") similar thumbnail images so that the viewing panel is not cluttered with numerous edits of an original image (or JPEG/RAW duplicates, as many cameras will save a JPEG alongside each RAW file generated); • Select and display groups of images in a flexible slideshow; • Send an image to an external application such as GIMP for processing. In summary, digiKam can be used both as a simple tool for organising a collection of images and a comprehensive image management system, depending on your specific needs. The following sections describe digiKam in more detail. 3. The digiKam desktop Sub­directories containing digital images are considered as digiKam "albums". When you open the program for the first time you see the desktop and are asked to confirm the locations of your albums and the digiKam database (these locations can be both internal, external or networked storage devices). The database contains thumbnail views of your images together with other items of information recorded by digiKam. You can change these settings later by selecting "settings > configure digiKam" in the menu at the top; (if you can't find this menu, try "Ctrl­M").

The digiKam desktop is divided into three panels:

The centr e panel displays the images contained in a selected album (sub­directory), either as thumbnails or a preview of a single image. The left ­ hand panel provides various ways of viewing your images. The initial view, obtained by clicking the top icon on the left­hand edge ("albums"), shows your albums in their directory/sub­directory trees on your storage media. The right­hand panel provides various ways of viewing and editing the properties of your images. The initial view, generated by the top icon on the right­hand edge ("properties"), displays general properties of the image selected in the centre panel. 4. The centre panel The centre panel displays thumbnails of the images in the selected album. Selecting a thumbnail and clicking on "preview image" enlarges the image to fill the panel. You can also do this by double­clicking on the thumbnail, with a single­click to return to thumbnail view.

Some image properties are displayed below each thumbnail. The properties displayed can be changed in the "settings > configure digiKam" menu Thumbnail size can be changed using a slider at the bottom of the screen. There is a small number near the botttom left­hand corner of two thumbnails in the screenshot above (xxx13 and xxx14) This indicates that these are groups. Similar images can be grouped (or stacked) by dragging and dropping one onto another. Clicking on a thumbnail selects the image, and several images can be selected in the usual manner by clicking with the Shift or Ctrl keys held down. Once selected, attributes can be assigned by right­clicking to bring up a menu of options; amongst the options are "assign/remove" tags and flags, "rename" and "open with" which generates a list of appropriate applications installed on the machine. A slideshow of selected images can be run by clicking the "slideshow" icon at the top. A right click on this icon produces the "advanced slideshow" menu where various configurations can be specified. Down the extreme left­ and right­hand edges of the desktop are two sets of icons which provide access to the side panels. Clicking on one of these icons expands the panel to display information specific to that icon. Clicking again removes the panel and enlarges the centre panel to fill the space. 5. The left­hand panel ­ viewing your images The following views are generated by the icons on the left­hand panel: Albums Tags Calendar Timeline Search Fuzzy searches Map search People

5.1 Albums As dscribed above, this displays the sub­directory structure of your images. Clicking on an album displays its images in the centre panel. DigiKam only displays the "albums" in the locations you've specified so, if there are images in locations not listed during the configuration stage, they will not show here. It may be worthwhile using digiKam to do an initial search of the entire hard disk before reducing the scope of future searches by specifying only certain sub­directories as albums.

5.2 Tags Images can be assigned "tags" (user­defined categories). All images similarly tagged can then be selected by clicking on the relevant tag in this view. 5.3 Calendar This view enables you to select images produced in a given year, month or day.

5.4 Timeline This is similar to the "calendar" view, but enables selection via a bar­chart view rather than a calendar. Time units of "day", "week", "month" or "year" can be selected. 5.5 Search This is a powerful tool. A "simple" search can be undertaken by typing the required criteria (e.g.U3A) in the search box. The search criteria can be saved for future use.

5.5.1 Advanced Search Four categories of metadata are available as search criteria, in addition to the simple (word) search.

The above four categories are expanded as shown here:

5.6 Fuzzy searches DigiKam scans the images and calculates a "signature" number (or footprint) for each. Similar images will have similar signatures and digiKam uses these to identify similar and duplicate images. Once the images have been scanned (which can take an hour or two for 10,000 images), clicking on "Duplicates" will generate lists of identical images. This is useful for removing duplicates from a disorganised collection.

Another way of using fuzzy searches is by dragging and dropping a thumbnail from any of the other views. When you drag it to the fuzzy searches icon, the side panel opens and you can drop the thumbnail onto the "Image" tab. DigiKam will search and dsiplay identical images. If you reduce the threshhold value (to 60% say), it will also identify similar but not identical images (see screenshot above).

The third tab, "Sketch", allows you to sketch a shape and look for similar images. I have no idea whether or not this works! 5.7 Map search This allows you to search by location for images with GPS data in their exif files. The map can be zoomed from the entire world to a street view. It demonstrates the capability of mobile phones for use as tracking devices.

5.8 People Both wonderful and scary!

Using fuzzy search techniques, the system scans your albums and identifies images containing faces. I've rediscovered several long­lost friends whilst using this view (e.g. the one on the bottom right).

Clicking on a face brings up a "Who is this?" box in which you can add names to the faces for subsequent searching. 6.0 The right­hand panel ­ viewing and editing image properties The following views are generated by the icons on the right­hand panel: Properties Metadata Colours Geolocation Caption/Tags Versioning Filters

6.1 Properties This screen displays high level information about the selected image. It is probably self­explanatory. 6.2 Metadata This displays extensive metadata (information about the image) for the selected image. The principal tabs are "EXIF" and "Makernote" (a sub­section of EXIF in which manufacturers add further data), but there are also "IPTC" and "XMP". IPTC is a standard for storing metadata developed by the international news agencies and XMP is an Adobe standard. The icons below EXIF at the top left of the panel allow you to select either a "full list" or a reduced "custom list" for each of these tabs, should you be so inclined. Note the search box at the bottom, with which you can interrogate the metadata.

6.3 Colours Two tabs here: "Histogram" and "ICC colour profile", useful when using digiKam's editing functions, but not considered in detail in this document (see Section 7.3). 6.4 Geolocation Whereas the MapSearch function on the left­hand sidebar is a search facility, this one merely displays the GPS data of a selected image. There are different views, including links to various mapping systems, of which Google Maps is shown here, and a "more information" tab at the bottom right corner which connects to the internet.

6.5 Captions/Tabs This is the first icon with which you can add information to an image. The icons above only allow you to view the metadata. This panel contains three tabs, mostly self­explanatory. "Description" enables you to add titles, captions, dates and star, colour & flag ratings (though these can also be added by right­clicking on an image thumbnail). Note the facility to "Apply to all versions" should there be a number of edits of the same image. "Tags" is where you can create and remove tag categories and add or remove them from images. You can work on multiple images by selecting them in the centre panelwith the Shift or Ctrl keys.

The "Information" tab enables you to add other data, such as copyright, location, contacts and subject details. It appears that you add this information via "templates" as I can't edit the various text boxes directly. Templates can be created by clicking the icon to the right of the template box, or opening the digiKam configuration screen (Settings > Configure digiKam > templates).

Note: Metadata can also be edited by using the main menu at the top of the desktop. "Image > Metadata", "Image > Geo­location" and "Image > Adjust Time & Date" provide useful functions. 6.6 Versioning I haven't quite worked out what this does, though it must be something to do with tracking the changes made to an image. 6.7 Filters The filters icon provides additional search options to those on the left­hand side panel. A set of images can be displayed using the search options in the left­hand panel and the selection can be further refined using the filters in the right­hand panel. Search options, as shown in the screenshot, are self­explanatory. The tags filter can also be used to apply tags by dragging and dropping image thumbnails onto appropriate tags. 7. Other functionality Three other functions in digiKam: the Camera Interface, the Light Table and the Image Editor, have not been considered in detail but are described briefly here. I have no detailed experience of them.

7.1 Camera Interface The camera interface enables you to transfer images via a wired connection between camera and computer. It provides various options for the destination sub­directories and can rename images during the import process. I prefer to import my images by copying from my camara card to the hard drive; then, when digiKam runs it automatically scans the albums for new and removed images and updates its database.

7.2 Light Table The light table is a tool for comparing pairs of images. It is useful for comparing different edits of an image or for reviewing duplicates prior to deleting unwanted files.

A series of images can be placed on the Light Table by selecting them and clicking the "Light Table" icon at the top of the screen (or Ctrl­L, or a right­click from within the selection). A new screen opens with the selected images appearing in a filmstrip. Images can be dragged from the filmstrip into the viewing panes and small green arrows appear in the filmstrip to indicate which image is in which pane. The right and left arrows can then be used to navigate through the filmstrip, keeping image in the left­hand pane constant and changing that in the right­hand pane. Selecting "By Pair" navigate through the filmstrip changing both images as you go. Selecting "Synchronise" in conjunction with "By Pair" enables you to zoom in and move around the images in the panes with the same action being applied to both; useful for more detailed comparisons. Since the light table is opens in a new screen, the original digiKam window remains active and the light table can be closed simply by closing its screen. 7.3 Image Editor The Image Editor provides a selection of editing tools. As with the Light Table, clicking the "Image Editor" icon (or F4, or a right­click from the selected image) opens the image in a new window. "Select Tool" gives access to the tools, which are well explained in the digiKam manual. I've tried several of the tools and they appear to work well.

8. The digiKam manual A digiKam handbook can be installed from the Linux Mint repository ("digikam­doc") and a .pdf file can be downloaded from the digiKam website: http://www.digikam.org/docs > digiKam PDF handbook. The handbook is unlikely to relate to the version of digiKam in the Mint repository (which is not the latest) but it provides a good explanation and a lot of useful background on file management and image editing. If you are interested in digiKam, it's worth reading.

Roger Hurley, 24th April 2014