1-2应用架构_可用性-Human Interface Guidelines（iOS用户界面指南）翻译

iOS为视觉障碍、听觉障碍和其它残障人士提供大量优化。大多数基于UIKit的app可以轻松的让更多的人使用你的app并拥有极佳的体验。

为图片、图标和界面元素提供可选的文本标签。可选的文本标签在屏幕上不可见，但是它们能让旁白知道屏幕上有什么，使视觉损伤的人更容易导航。

 If your app uses UIKit to implement落实 its user interface, text and interface elements automatically adapt to certain accessibility preferences, such as bold and larger text. Your app should also check and respond to accessibility preferences when appropriate适当的, such as when the option to reduce减少 motion动作 is enabled开启. Apps implementing实行 custom fonts should attempt to match the accessibility behavior of the system fonts.

相应可访问性的首选项。如果你的app用UIKit设计用户界面、文字和交互元素时自动匹配某个可用性选项比如更粗和更大的文本。当可用性选项变更时，你的app也应当在合适的时候进行核对和调整。app在使用自定义字体时也应该尝试匹配系统字体的可用性。

Test your app with accessibility features. In addition to text and motion手势 changes, accessibility options can change contrast对比度, invert colors反相, reduce transparency, and more. Enable能够使 these settings and observe观察 how your app will look and behave for people who enable these features.

用辅助功能测试你的app。可用性选项除了能改变文本、手势，还能改变对比度、颜色反相、降低透明度等等。启用这些设置来观察那些开启这些功能的用户看到的app是什么样子的。

Include closed captions说明 and audio descriptions摘要. Closed captions allow the deaf and hard-of-hearing to perceive理解 spoken dialogue对话 and other audible content in videos. Audio descriptions provide spoken narration of important video content for the visually impaired.

包含隐藏的字幕和音频说明。隐藏的字幕能够让聋人和听力障碍者能够理解口语对话和其它视频中的声音。视频摘要为视觉障碍者提供视频中重要内容的口头叙述。

Use sufficient足够的 color contrast ratios. Insufficient不足的 contrast in your app makes content hard to read for everyone. Icons and text might blend融合 with the background, for example. An online color contrast calculator can help you accurately analyze the color contrast in your app, to ensure that it meets optimal standards. Strive努力 for a minimum contrast ratio of 4.5:1, although 7:1 is preferred because it meets more stringent严格的 accessibility standards. 

使用足够的颜色对比度。你app中不足的对比度使内容让所有人都难以阅读。例如，图标和文本可能和背景融合在一起。一个在线的颜色对比度计算器能够帮助你正确的分析你的app中颜色的对比度，以确保符合最佳的设计。尽量让对比度高于4.5:1，7:1是最佳的选择，因为这样能够更符合可用性标准。