|Stable release||(February 24, 2010 ) [+/−]|
|Operating system||Microsoft Windows, Linux, Mac OS X|
|Type||Digital photo organizer|
Picasa is a software application for organizing and editing digital photos, originally created by Idealab and owned by Google since 2004. "Picasa" is a blend of the name of Spanish painter Pablo Picasso, the phrase mi casa for "my house" and "pic" for pictures (personalized art). In July 2004, Google acquired Picasa and began offering it as a free download. At the time of the acquisition, the company's management team consisted of Lars Perkins as CEO, Mike Herf as CTO, and Dan Engel as VP Market Development.
Native applications for Windows XP, Windows Vista, Windows 7 and Mac OS X are available through Google Labs. For Linux Google has bundled Wine with the Windows version to create an installation package rather than write a native Linux version. For Windows 98, Windows Me and Windows 2000, only an older version is available. There is also an iPhoto plugin or a stand-alone program for uploading photos available for Mac OS X 10.4 and later.
For organizing photos, Picasa has file importing and tracking features, as well as tags, facial recognition, and collections for further sorting. It also offers several basic photo editing functions, including color enhancement, red eye reduction and cropping. Other features include slide shows, printing and image timelines. Images can also be prepared for external use, such as for e-mailing or printing, by reducing file size and setting up page layouts. There is also integration with online photo printing services.
Picasa uses picasa.ini files to keep track of keywords for each image. In addition to this, Picasa attaches IPTC keyword data to JPEG files, but not to any other file format. Keywords attached to JPEG files in Picasa can be read by other image library software like Adobe Photoshop Album, Adobe Bridge, digiKam, and iPhoto.
Picasa has a search bar that is always visible when viewing the library. Searches are live in that displayed items are filtered as you type. The search bar will search filenames, captions, tags, folder names, and other metadata.
Picasa also supports boolean operators for searching in much the same way as Google's web search. All search terms are required by default (as with the operator "AND"), and images tagged with specified keywords can be excluded by using the hyphen (as in the boolean operator "NOT"). For example, searching for family children -friends will cause Picasa to display all images with the keywords "family" and "children", but which do not include the keyword "friends".
Picasa also has an experimental feature in the search bar where images can be searched for that contain certain colors with the "color:" operator.
Picasa has no separate view window. There is only an "edit view" with a viewing area. Fullscreen view is available in slideshow mode, by holding down the ctrl+alt keys while in "edit view", or by pressing the Alt Gr key. This feature is also available through the context menu of Windows Explorer, and provides a way to start the Picasa editor as well.
In Picasa 2 and earlier versions, changes to pictures made in Picasa overwrite the original file, but a backup version of the original is saved in a hidden folder named "Originals" in the same folder as the original picture.
In Picasa 3, changes to pictures made in Picasa are saved to a hidden file picasa.ini in the same folder as the original picture. This allows multiple edits to be performed without altering the original image. Viewing the picture in Picasa or using the Picasa Photo Viewer will apply modifications on the fly, whereas viewing through other programs (such as Windows XP's Photo and Fax Viewer) will display the original image. Changes can also be made permanent using the "Save" function, where the original file is backed up and the modified version is written in its place, similar to version 2.
On 15 August 2006, Google announced it had acquired Neven Vision whose technology can be used to search for features within photos such as people or buildings. Google applied this technology for face recognition and this functionality was launched on Picasa Web Albums on 2 September 2008.
Neven Vision incorporates several patents specifically centered around face recognition from digital photo and video images. Neven Vision's technology was among the top finishers in both the FERET 1997 and FRVT 2002 independent tests comparing the world's best face recognition technologies.
Since version 3.5 of Picasa, Google Earth is not needed. Geotagging may be done directly inside Picasa, using a more practical Google Maps component, which enables this functionality in the Mac OS X version.
It allows users with accounts at Google to store and share 1 GB of photos for free.
Users may upload pictures through a variety of ways; via the PWA web interface on supported browsers, Picasa 2.5.0 or later on Microsoft Windows, using the Exporter for iPhoto, the Aperture to Picasa Web Albums plug-in, Uploader on Mac OS X,, F-Spot on Linux or through WAManager in the Amiga-like OS MorphOS. In both paid and free accounts, the actual resolution of the photo is maintained (even though a smaller resolution photo may be displayed by the web interface).
In Picasa 3 versions of the software, using the 'original size' upload option, pixel size remains the same, but JPEG compression is increased significantly during upload to PWA. As JPEG is a 'lossy' format, some picture information (and quality) is lost. Picasa 3.6 added an option to preserve original JPEG quality.
PWA uses an "unlisted number" approach for URLs for private photo albums. This enables a user to email a private album's URL to anyone s/he wants; the recipient can view the album without having to create a user account - this is done via an "authentication key" that's needed to be appended to the URL for the album to be shown. The Picasa help files say that private albums are not searchable by anyone except the user. Recently, a new option, named "sign-in required to view" was added to album visibility. This makes the album viewable only to those with whom the album is explicitly shared.
Ads are shown on the free Picasa Web Albums accounts. The Terms of Service permit Google to use the uploaded photos to display on the website or via RSS feeds, and also for promoting Google services royalty-free.
Picasa Web Albums was first leaked on 6 June 2006. When introduced, it came with 250 MB free space. On 7 March 2007 it was upgraded to 1 GB. Users can also rent additional storage space (shared between Google services such as Gmail and Picasa Web Albums) from 20 GB to 16 TB. 
Hello by Google's Picasa was a free computer program that enabled users to send images across the Internet and publish them to their blogs. It was similar to an instant messaging program because it allowed users to send text, but Hello focused on digital photographs. Users can opt to view the same pictures as their friends in real-time. One of the advantages claimed at the website is that photos could be shared through firewalls.
Hello's service was canceled at the end of 2006, and users were instructed to try the Picasa 'Blog This' functionality for uploading pictures to their blogs. According to the official website, the Hello project was shut down on 11 June 2008.
There are no versions of Picasa for Windows 95 or NT. The latest version offered for Windows 98/ME is 2.0.0 (build 18.84). The latest version offered for Windows 2000 is 2.7 (build 37.64). Newer versions are for Windows XP, Vista and 7 only.
As from about early June 2006, Linux versions (2.2.2820-5) became available as free downloads for most distributions of the Linux operating system. It is not a native Linux program but an adapted Windows version that uses the Wine libraries.
Google announced that there will be no Linux version for 3.5, due to low adoption.
On 5 January 2009 Google released a beta version of Picasa for Mac (Intel-based Macs only). Also, a plugin is available for iPhoto to upload to the Picasa Web Albums hosting service. There is also a standalone Picasa Web Albums uploading tools for OS X 10.4 or later.