The intent of this Success Criterion is to encourage authors, who are using technologies which are capable of achieving their desired default visual presentation, to enable people who require a particular visual presentation of text to be able to adjust the text presentation as needed. This includes people who require the text in a particular font size, foreground and background color, font family, line spacing or alignment.
If authors can use text to achieve the same visual effect, they should present the information as text rather than using an image. If for any reason, the author cannot format the text to get the same effect, the effect won't be reliably presented on the commonly available user agents, or using a technology to meet this criterion would interfere with meeting other criteria such as 1.4.4, then an image of text can be used. This includes instances where a particular presentation of text is essential to the information being conveyed, such as type samples, logotypes, branding, etc. Images of text may also be used in order to use a particular font that is either not widely deployed or which the author doesn't have the right to redistribute, or to ensure that the text would be anti-aliased on all user agents.
Images of text can also be used where it is possible for users to customize the image of text to match their requirements.
The definition of images of text contains the note: This does not include text that is part of a picture that contains significant other visual content. Examples of such pictures include graphs, screenshots, and diagrams which visually convey important information through more than just text.
The Success Criterion is intended to address situations where images of text are used rather than text. Where images of text are used in addition to text to convey the same information, and where both are presented to the user, this Success Criterion is met. This allows authors to convey content using any styling they desire, while also presenting the information in text, which can then be manipulated by users to make it more distinguishable. This is in contrast to 1.4.9 Images of Text (No Exception), which applies to all images of text, regardless of whether or not they are used in addition to text.
Techniques for satisfying this Success Criterion are the same as those for Success Criterion 1.4.9, except that they only need to apply if the visual presentation can be achieved with the technologies that the author is using. For Success Criterion 1.4.9, the sufficient techniques would be applied only when the user can customize the output.
See also 1.4.9 Images of Text (No Exception).