iOS 8人机交互指南（10）
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10. 颜色与排版（Color and Typography）
10.1 颜色加强交流（Color Enhances Communication）
In iOS, color helps indicate interactivity, impart vitality, and provide visual continuity. The built-in apps use a family of pure, clean colors that look great individually and in combination, and on both light and dark backgrounds.
在 iOS 中，颜色有助于表达交互性、透露活力，也提供了可视化的连续性。内置 app 使用一系列无论单看还是组合都看上去不错的、纯粹干净的颜色，而且这些颜色无论背景明暗都有较好效果。
内置 app 的颜色
If you create multiple custom colors, make sure they work well together. For example, if pastels are essential to your app’s style, you should create a family of coordinating pastels that can be used throughout the app.
如果创建多种自定义颜色，那一定要保证它们搭配得很好。例如，如果 app 的风格是轻柔的彩色，那就应该创建一系列协调搭配的彩色并在 app 中使用。
Pay attention to color contrast in different contexts. For example, if there’s not enough contrast between the navigation bar background and the bar-button titles, the buttons will be hard for users to see. A quick but unscientific way to find out if your colors have sufficient contrast is to view your app on a device in different lighting conditions, including outdoors on a sunny day.
注意在不同环境下使颜色有差异。例如，如果导航栏背景和上面的按钮标题颜色差异不够明显，那用户就很难看到按钮。有一种快速但不够科学的方法来验证颜色是否有足够的差异性，那就是在一个不同的光线条件下的设备里查看 app，包括阳光明媚时的户外。
Although viewing your app on a device can help you find some of the areas you need to work on, it's no substitute for a more objective approach that yields reliable results. This approach involves determining the ratio between the luminance values of the foreground and background colors. To get this ratio, use an online contrast ratio calculator or you can perform the calculation yourself using the formula established in the WCAG 2.0 standard. Ideally the color contrast ratio in your app is 4.5:1 or higher.
虽然这种方法有助于发现那些有待继续改进的区域，但它还是不能替代一个获得可靠结果的更客观的方法。这个方法涉及到前景色与背景色亮度值间的比例如何。为了获得这一比例，使用在线差异率计算器或者使用基于 WCAG 2.0 标准的公式自己计算。理想情况下，颜色差异率应该为 4.5：1 或者更高。
Take bar translucency and app content into account when you use a custom bar tint. If you need to create a bar tint that matches a specific color, such as a color in an existing brand, you may have to experiment with various colors before you get the results you want. A bar’s appearance is affected by both the translucency that iOS provides and the appearance of the app content that can be behind the bar.
使用自定义栏提示的时候，要考虑栏的透明度和 app 内容。如果需要创建栏提示来匹配一个特定颜色，例如一个已存在的品牌的颜色，那需要在获得满意效果前进行多种颜色的验证。栏的外观同时受 iOS 提供的透明度和栏下面的 app 内容显示两个因素的影响。
后一篇：iOS 8人机交互指南（11）
