IOS icon尺寸

http://developer.apple.com/library/ios/#documentation/userexperience/conceptual/mobilehig/IconsImages/IconsImages.html

Description	Size for iPhone and iPod touch (in pixels)	Size for high-resolution iPhone and iPod touch (in pixels)	Size for iPad (in pixels)	Size for high-resolution iPad (in pixels)	Guidelines
Application icon (required for all apps)	57 x 57	114 x 114	72 x 72	144 x 144	“Application Icons”
App icon for the App Store (required for all apps)	512 x 512	1024 x 1024 (recommended)	512 x 512	1024 x 1024 (recommended)	“Application Icons”
Launch image (required for all apps)	320 x 480	640 x 960	768 x 1004 (portrait) 1024 x 748 (landscape)	1536 x 2008 (portrait) 2048 x 1496 (landscape)	“Launch Images”
Small icon for Spotlight search results and Settings (recommended)	29 x 29	58 x 58	50 x 50 (Spotlight search results) 29 x 29 (Settings)	100 x 100 (Spotlight search results) 58 x 58 (Settings)	“Small Icons”
Document icon (if necessary for custom document types)	22 x 29	44 x 58	64 x 64 320 x 320	128 x 128 640 x 640	“Document Icons”
Web clip icon (recommended for web apps and websites)	57 x 57	114 x 114	72 x 72	144 x 144	“Web Clip Icons”
Toolbar and navigation bar icon (optional)	Approximately 20 x 20	Approximately 40 x 40	Approximately 20 x 20	Approximately 40 x 40	“Icons for Navigation Bars, Toolbars, and Tab Bars”
Tab bar icon (optional)	Approximately 30 x 30	Approximately 60 x 60	Approximately 30 x 30	Approximately 60 x 60	“Icons for Navigation Bars, Toolbars, and Tab Bars”
Default Newsstand cover icon for the App Store (required for Newsstand apps)	At least 512 pixels on the longest edge	At least 1024 pixels on the longest edge	At least 512 pixels on the longest edge	At least 1024 pixels on the longest edge	“Newsstand Icons”