Aperture 1.5: Preview Storage
2006-10-04
When Aperture upgraded its library the first time 1.5 ran, it changed a few things. One of the things it did was to add a new file called ApertureData.xml to the library. Here is the top level of a small library (opened by control-clicking and selecting Show Package Contents) before the update:
and here it is after the update:
Opening that file XML with a text editor, or better still an XML editor like Property List Editor shows it to be a complete description of all of the previews and where they can be found. In fact it shows two locations: a preview in a Preview folder and a another in a Thumbnail folder.
The purpose of this XML file is to allow other applications such as Keynote to dive into the library and pull out a list of albums and projects, present them to the user for browsing with names and thumbnails, and then fetch the high resolution preview image. In this way, Keynote does not have to mess with Aperture's folder structure, database, or built-in image thumbnails that are used for screen display. And Aperture does not have to be running. An application like Keynote can also keep a copy of some of that data so it can present the user with a window of thumbnails quickly and then update it as it scans and processes in the background.
When you quit Aperture it will sometimes pause while it writes this file to disk. You may see a dialog box appear to this effect.
If I drill down into the project and the import session to the folder with my butterfly image inside, I see the following files:
This image is managed so the original is here too, that's the first file. The .apfile file is a file that helps Aperture maintain the integrity of the file project structure. And the .apmaster and .apversion files describe to Aperture how to process the master for display, including RAW conversion and adjustments. But none of those have any information about previews -- previews are sort of tagged on.
What is new in 1.5 is that there are two folders added: Previews and Thumbnails. The former holds the generated previews for all versions. These can be as big as the master, or can be limited in size by the choice in the prefs window. They do contain metadata, so that is available to any application that can extract it from the JPG file. The thumbnail is always fitted to a 240x240 pixel square. Here is the one from the window above:
So this mechanism, XML file for information and JPG files for data, provides a parallel and independent image system for Aperture. It means that Aperture does not have to know anything about the applications that use the images, and the applications do not need to know anything about how Aperture works or where the originals are or how they were prepared. It is a very simple system.
and here it is after the update:
Opening that file XML with a text editor, or better still an XML editor like Property List Editor shows it to be a complete description of all of the previews and where they can be found. In fact it shows two locations: a preview in a Preview folder and a another in a Thumbnail folder.
The purpose of this XML file is to allow other applications such as Keynote to dive into the library and pull out a list of albums and projects, present them to the user for browsing with names and thumbnails, and then fetch the high resolution preview image. In this way, Keynote does not have to mess with Aperture's folder structure, database, or built-in image thumbnails that are used for screen display. And Aperture does not have to be running. An application like Keynote can also keep a copy of some of that data so it can present the user with a window of thumbnails quickly and then update it as it scans and processes in the background.
When you quit Aperture it will sometimes pause while it writes this file to disk. You may see a dialog box appear to this effect.
If I drill down into the project and the import session to the folder with my butterfly image inside, I see the following files:
This image is managed so the original is here too, that's the first file. The .apfile file is a file that helps Aperture maintain the integrity of the file project structure. And the .apmaster and .apversion files describe to Aperture how to process the master for display, including RAW conversion and adjustments. But none of those have any information about previews -- previews are sort of tagged on.
What is new in 1.5 is that there are two folders added: Previews and Thumbnails. The former holds the generated previews for all versions. These can be as big as the master, or can be limited in size by the choice in the prefs window. They do contain metadata, so that is available to any application that can extract it from the JPG file. The thumbnail is always fitted to a 240x240 pixel square. Here is the one from the window above:
So this mechanism, XML file for information and JPG files for data, provides a parallel and independent image system for Aperture. It means that Aperture does not have to know anything about the applications that use the images, and the applications do not need to know anything about how Aperture works or where the originals are or how they were prepared. It is a very simple system.
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