LASIImageView – download image with progress indicator
翻译原网址：http://lukagabric.com/lasiimageview-download-image-with-progress-indicator/#more-797
LASIImageView is a UIImageView subclass that supports asynchronous image download with different progress indicators. It is possible to choose among three different progress indicator styles, with or without percent text.
LASIImageView继承自UIImageView，支持异步下载图片，并在图片上显示下载进度指示条。当然，你可以选择3种不同的指示条显示风格，每种指示条风格都可以显示或者不显示数字百分比。
In order to use it, just add LASIImageView class files to the project and set the instance imageUrl property to download and display the image.
使用很简单，把LASIImageView类拖入到你的工程中，设置好属性imageUrl，然后显示图片。
LASIImageView includes shared appearance settings. Appearance can also be specified for any LASIImageView instance, overriding the global appearance for that object.
LASIImageView包含全局显示的设定。当然呢，你也可以给任意指定的LASIImageView单独设定，用你新设定的值覆盖全局的那个值即可。
ASIHTTPRequest is used for image download. Request settings can be set for LASIImageView instances globally, or per instance, overriding the global settings.
ASIHTTPRequest开源库用来下载图片。网络请求的设定可以用来给LASIImageView设定全局的值，或者给每一个实例对象单独设置（新赋值覆盖全局的值即可）。
On request finished – success or fail blocks are called (LASIImageViewDownloadFinishedBlock or LASIImageViewDownloadFailedBlock).
当网络请求结束后，成功或者失败的block将会被调用。
LASIImageView is hosted on my GitHub