iOS 设置高清图片

Applications running in iOS 4 should now include two separate files for each image resource. One file provides a standard-resolution version of a given image, and the second provides a high-resolution version of the same image. The naming conventions for
each pair of image files is as follows:

Standard: <ImageName><device_modifier>

.

<filename_extension>

High resolution: <ImageName>

@2x

<device_modifier>

.

<filename_extension>

The <ImageName> and <filename_extension> portions of each name specify the usual name and extension for the file. The
<device_modifier> portion is optional and contains either the string

~ipad

or

~iphone

. You include one of these modifiers when you want to specify different versions of an image for iPad and iPhone. The inclusion of the

@2x

modifier for the high-resolution image is new and lets the system know that the image is the high-resolution variant of the standard image.