usability - 如何为图像编写良好的替代文字，以帮助屏幕阅读器和盲人理解图片的含义？

Question

如何为图像编写良好的替代文字，以帮助屏幕阅读器和盲人理解图片的含义？如果我们使用的是Alt文本，那么在特殊情况下(例如菜单图像等)都使用的话，Title =“text”应该是

Answer 1

您不应让视障用户了解图像的全部含义。对于盲人来说，有效的图像不存在，仅存在文字。
alt 文本应作为可替换图像的单个句子/段落，传达相同的内容，并且在相邻内容的上下文中仍然有意义。
如果图像是GUI的一部分，则alt文本应传达一个 Action (动词)，换行，回答或退出。
您应该使用 links 访问您的网站，并尝试了解您的网站。例如，如果有一个饼图，则其alt文本应该是百分比的一小部分摘要。如果您在博客文章旁边只有一朵漂亮的花，请不要给它添加像324＃博客文章的花卉图片伴侣之类的疯狂alt文本，甚至更糟的flower.jpg。
如果图像对于导航或获取信息很重要，请尝试为其提供alt文本，以使站点无需图像即可工作。如果图像仅是呈现图像，请为其提供一个空的alt文本。
据我所知， title 仅在悬停时才显示，因此它们应该为图像提供额外的信息，因此应避免useless duplication of information。对于屏幕阅读器来说，这有点棘手，因为用户之间的支持和配置可能会非常不同。
一些empirical data将title显示为无用的:

• Most users of screen reading software do not change their default settings to access the TITLE attribute information on links.
• Most screen reading software can access TITLE attribute content on form controls by default.
• Some screen reading software cannot access TITLE attribute information.
• Users of screen magnifiers can read TITLE attribute text at lower magnification levels.
• Users of screen magnifiers cannot read TITLE attribute text, that contains more than 1 or 2 words, at higher magnification levels.

Here's good piece of advice，比我可以放的更好

Use this to provide additional information that is not essential. Most visual browsers display title text as a tool tip when the element is hovered over, however it is up to the browser manufacturer to decide how the title text is rendered. Some will display the text in the status bar instead. Early versions of Safari did this, for instance.

One good use of the title attribute is to add descriptive text to links, especially if the link text itself doesn’t clearly describe the link’s destination. This way you can help visitors know where the link will take them, possible saving them from loading a page only to find out it wasn’t anything they’re interested in. Another potential use is to provide additional information for an image, like maybe a date or other information that is likely not essential.

请记住， longdesc 属性应该是指向更多信息的链接，而不是某些人误用的文本。