Designed to let users easily create, play and share presentations, Keynote contains most of the features found in modern presentation software, such as a slide navigator, the ability to add tables, shapes and charts to slides and a powerful media browser which allows users to drag and drop music from from iTunes, and photos from iPhoto and Aperture into their slides.
Keynote contains a large number of pre-designed themes to let users select common presentation formats, and powerful graphics tools to manipulate embedded images and provide advanced 3D transitions between slides (powered by OpenGL). The major Keynote releases are summarised below:
First version - basic features - Import Powerpoint presentations, slide navigator, graphics support for rotations, resizing and opacity, charts and slide transitions.
Released in iWork '05. Contained improved animations for slides and text, iLife media browser, new themes, more presenter controls, embedded hyperlinks and the ability to export presentations to Macromedia Flash.
Released in iWork '06 with new themes, HD-capability, improved graphing and table features, cinematic transitions and 3D graphs.
Released in iWork '08 with easier to use animation features, new templates, smart builds (for predefined animations), instant alpha (for removing backgrounds from photographs), and a new narration to add a voiceover to slideshows.
Released in iWork '09. Contains support for MathType equations, a new share menu, trackpad support, "magic move" (for easier transitions), improved presenter tools, but removed support for exporting to Flash.
Added support for Mac OS X Lion, and included support for full screen functionality, auto-save, resume and versioning. Also with improved compatibility with Microsoft Office.
Support added for iCloud documents and Retina displays.
Adds Keynote support for iOS 6.0
Part of new iWork suite for Mac, with 64-bit support and iCloud syncing.
Improved compatibility with Microsoft Powerpoint.
Updated design of OS X Yosemite, iOS 8 and a new file format to improve support for 3rd party online services.
A .key file is actually a compressed ZIP file comprised of a number of other different files combined that together make up a .key file. The most recent version of Keynote saves files with an "Index" directory containing Apple's proprietary IWA file format, a "Metadata" directory with .plist files, a "Data" directory with image assets (e.g. backgrounds and photos used in slides) and one or more jpg files for allowing quick previews.
Files created by Keynote in iWork cannot be opened by programs other than iWork.
JPG's are often used for web sites and email as they are generally smaller file sizes as they are lossy meaning that some image quality is lost when the JPG is compressed and saved. The resultant 'lossy' file means that quality can never be recovered. The JPG format is often used in digital camera memory cards. The JPG file is a great format as it often manages to compress files to 1/10 of the size of the original file which is especially good for saving on bandwidth.
JPG is a graphical file format for editing still images, it offers a symmetrical compression technique which is processor intensive and time consiming in both compression and decompression. JPEG is a joint standard of the International Telecommunications Union (ITU-T T.81) and the International Organization for Standardization (ISO 10918-1). JPEG involves a lossy compression mechanism using discrete cosine transform (DCT). Compression rates of 100:1 can be achieved, although the loss is noticeable at that level. Compression rates of 10:1 or 20:1 yield little degradation in image quality.
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