About Core Image
Core Image is an image processing and analysis technology designed to provide near real-time processing for
still and video images. It operates on image data types from the Core Graphics, Core Video, and Image I/O
frameworks, using either a GPU or CPU rendering path. Core Image hides the details of low-level graphics
processing by providing an easy-to-use application programming interface (API). You don’t need to know the
details of OpenGL or OpenGL ES to leverage the power of the GPU, nor do you need to know anything about
Grand Central Dispatch (GCD) to get the benefit of multicore processing. Core Image handles the details for
you.
Core Image 是一种处理图片的技术，可用来实时处理视频流图片。它处理的 image data 可以来自于 Core Graphics，Core
Video 以及 Image I/O 框架，使用GPU或者CPU来渲染。Core Image 隐藏了低级别API，给你提供易于使用的API。你不需要
知道OpenGL或者OpenGL ES的知识就可以驾驭GPU，甚至你都可以不知道任何的GCD的知识但却可以获取到多处理器处理图
片的便利。你只需要用就行了：）。
Core Image in relation to the operating system
Core Image 与操作系统之间的关系：
At a Glance
The Core Image framework provides:
● Access to built-in image processing filters
● Feature detection capability
● Support for automatic image enhancement
● The ability to chain multiple filters together to create custom effects
概要：
Core Image framework提供了：
* 可以使用内置的处理图片的滤镜
* 特征检测的能力（比如面部识别什么的）
* 图片效果自动增强
* 将多个滤镜合并成滤镜链组合形成新的滤镜效果
Core Image is Efficient and Easy to Use for Processing and Analyzing Images
使用Core Image来处理、分析图片是很简单的。
Core Image provides more than 90 built-in filters on iOS and over 120 on OS X. You set up filters by supplying
key-value pairs for a filter’s input parameters. The output of one filter can be the input of another, making it
possible to chain numerous filters together to create amazing effects. If you create a compound effect that
you want to use again, you can subclass CIFilter to capture the effect “recipe.”
在iOS中，Core Image 提供了超过90个的内建滤镜，OS X中有120个。你只需给滤镜提供键值对就能设置滤镜。一个滤镜的输
出可以作为另外一个滤镜的输入，因为具备这样子的特性，所以你可以将几种滤镜组合在一起使用，可以用来创造出难以置信的
效果，你可以通过继承关系将几种滤镜合并在一起：）。
There are more than a dozen categories of filters. Some are designed to achieve artistic results, such as the
stylize and halftone filter categories. Others are optimal for fixing image problems, such as color adjustment
and sharpen filters.
滤镜的种类分为很多很多种。有些是用来实现艺术效果，比如styleze以及halftone滤镜集。有些是用来优化处理图片效果的，
比如颜色调节以及锐度调节滤镜。
Core Image can analyze the quality of an image and provide a set of filters with optimal settings for adjusting
such things as hue, contrast, and tone color, and for correcting for flash artifacts such as red eye. It does all
this with one method call on your part.
Core Image 可以分析图片并提供一系列的滤镜来设置图片的锐度值、对比度值或者颜色等等。为了消除照片的红眼，你只需要
使用一个方法就可以解决这个问题。
Core Image can detect human face features in still images and track them over time in video images. Knowing
where faces are can help you determine where to place a vignette or apply other special filters.
Core Image 可以识别人脸的特性，在存在的照片中或者是视频流中都可以使用。
Core Image Can Achieve Real-Time Video Performance
Core Image 能够处理实时录像。
If your app needs to process video in real-time, there are several things you can do to optimize performance.
如果你的app需要处理实时录像，你可以用好几种方式来实现这种效果。