Use LightZone from F-Spot as external editor

In a previous post I have shown how to teach LightZone, a non-destructive photo editor, to open files passed from the command-line (for some strange reason it doesn't do it out-of-the-box).

Now, I want to be able to use LightZone as an external editor from F-Spot, which I use for my photo workflow.

F-Spot has a convenient Open With menu when right-clicking on a photo, we just need to add LightZone to this menu. After some research, it appear that F-Spot uses the standard desktop entry specification files to populate this menu. These files can be located either in /usr/share/applications or in user's home, ~/.local/share/applications. You can use either location, but I prefer the latter one, because I have unpacked LightZone into my home as well.

Here is the working lightzone.desktop file:

[Desktop Entry]
Version=1.0
Type=Application
Name=LightZone Photo Editor
Exec=LightZone %u
TryExec=LightZone
Icon=/home/USERNAME/LightZone/LightZone_32.png
Terminal=false
Categories=Graphics;2DGraphics;Photography;RasterGraphics;GTK;
StartupNotify=true
MimeType=image/tiff;image/jpeg;image/x-canon-cr2;image/x-canon-crw;image/x-nikon-nef;image/x-pentax-pef;

This file expects that you have followed the previous post and already have LightZone in the PATH which accepts a filename to open on the command-line.

• Exec - this line specifies what command to run, %u means to pass the selected file's URL on the command-line. For some reason with trial and error, I found that F-Spot is only able to pass URLs like this, specifying %f doesn't work with F-Spot. But if you look at the LightZoneOpener.java source, you will see that it supports URLs as well as filenames.
• Icon - change this one to the full path of LightZone's icon, it supplied in the original archive.
• Categories - this specifies where LightZone will appear in the ''Applications'' menu.
• MimeType - here you must list all image mime types that you want LightZone to open. This is especially important for RAW files. As I own a Canon camera, I have most of my photos in CR2 format, so I need to be sure that image/x-canon-cr2 is in the list. I have also specified CRW, NEF and PEF mime types for older Canon, Nikon and Pentax cameras, respectively. These mime types are already registered in Ubuntu Intrepid (not sure about other distributions). Here is some info on how to register new mime types in Gnome, in case your camera's format is not registered yet.
  

After chosing the Open With->LightZone, F-Spot will ask whether to create a new version for the file. Select 'No' - this won't work with RAW files and LightZone anyway, because LightZone saves files automatically with the _lzn.jpg suffix and F-Spot doesn't know about it.

Getting this right requires patching F-Spot (I am going to do that later). For now, you will have to import the saved file manually, if you want it to appear in F-Spot.

Opening files with LightZone from command-line

LightZone is a very useful commercial photo editor with some unique features like non-destructive and layer-based editing. To my mind, the developers has taken a very clever approach to save resulting edits inside of smaller-size JPEG files (thumbnails), so that any program can be used for previewing the resulting image, but opening of the file in LightZone will load the original image and show all the edits again with the possibility to make any changes and export a full-resolution image. The cool thing here is that edited files are very small especially when compared to 10Mb+ source RAW photos, contain all the editing history and can be previewed quickly with any software. And all this runs on Linux (thanks to Java - write once, run almost anywhere).

The only problem with LightZone (at least the Linux version) is that it doesn't accept filenames from the command-line! You have to start the program and select the file manually using the embedded file browser. Of course, this is not an option if you want to run LightZone from another application as an external editor, eg from F-Spot (more on this in a later post).

To make a long story short, I have written a small Java program that takes a filename on the command-line and then modifies LightZone preferences, so when you run it next time it will directly open the specified image.

Here it is:

import java.io.*;
import java.net.*;
import java.util.prefs.*;

/**
 * LightZoneOpener - will modify LightZone preferences to open the 
 * specified file (image) on next startup.
 * This is useful to force LightZone to open a particular file from 
 * the command-line, just run this code before starting LightZone. 
 *
 * @author Anton Keks
 */
public class LightZoneOpener {

  public static void main(String[] args) throws Exception {
    if (args.length != 1) {
      System.err.println("Please specify filename to open in LightZone");
      System.exit(1);
    }
    String filename = args[0];
    if (filename.startsWith("file:"))
      filename = new URI(filename).getPath();
    File file = new File(filename).getCanonicalFile();
    if (!file.exists()) {
      System.err.println(file + " doesn't exist!");
      System.exit(2);
    }
    File fileDir = file.getParentFile();
    
    // set image folder as current one
    Preferences folderPrefs = Preferences.userRoot().node("com/lightcrafts/ui/browser/folders");
    int i = 0; File dir = file;
    while ((dir = dir.getParentFile()) != null) {
      folderPrefs.put("BrowserTreePath" + i++, dir.getName().isEmpty() ? "/" : dir.getName());
    }
    folderPrefs.remove("BrowserTreePath" + i);
    
    // set selected image in the current folder
    Preferences appPrefs = Preferences.userRoot().node("com/lightcrafts/app");
    appPrefs.put("BrowserSelectionMemory" + fileDir.getPath().hashCode(), file.getPath());
    // tell LightZone that last startup was OK just in case
    appPrefs.put("StartupSuccessful", "true");
    
    System.out.println("LightZone is now ready to open " + file + " on next start");
  }
}

Here is what to do:

1. save it to LightZoneOpener.java
   
2. compile with javac LightZoneOpener.java
3. run with java LightZoneOpener

Then you can create a small script that will automate the stuff for you (save it to ~/bin/LightZone):

#!/bin/bash
java -cp ~/bin LightZoneOpener "$@"
~/LightZone/LightZone

This assumes that you have extracted LightZone to ~/LightZone (in your home dir) and have the following two files in the ~/bin dir: the compiled LightZoneOpener.class and the script file LightZone (don't forget to set the execute permission with chmod a+x ~/bin/LightZone)

Here is all this pre-compiled. Just extract the file directly in your home and it will put all needed files into the bin directory. After next login your local bin will be in $PATH, so you will be able to use it.

Now you can run LightZone filename on the command-line in Linux (or using Alt+F2)! Have fun!