Today, there are many ways to create accessible alternatives for graphical content in a digital book. Images can be described in the text of a book, or the descriptions can be coded so they can be voiced by reading devices or text-to-speech software. The image can be separately produced as a tactile graphic using a variety of techniques that place a raised image on paper or render it as a tactile audio display (tactile graphic accompanied by audio description). MathML can be used to make both the structure and the content of mathematical and chemical notations, accessible. Certain chemistry images can also use chemical notation braille code, Scalable Vector Graphics, and chemical file formats. Sonification is a modality that provides non-speech audio to represent a graphed equation. Haptics and Three-dimensional models can be made for the student to touch. MusicXML, MIDI, and standard audio files can be used to access musical notations. Fortunately, there are many options to support accessible images, and these modalities will be outlined in the samples included in this book.
While options exist, few people outside of a small community of alternate media producers and consumers have seen, heard, or touched these alternate methods of accessing graphical content. As educational materials migrate from paper to electronic media, the opportunity exists to employ many of these alternatives to images, reduce the number of steps required to create an accessible digital book, and ensure that all content “born digital” is also “born accessible.”
Deciding what images should be made accessible and how best to make them accessible is a complex process. Some guiding questions to consider, while making these decisions, include:
- What information does the image convey?
- Is this information included in the surrounding text or caption?
- What is the purpose of the image? Is it presented to provide a general understanding of a concept (map in Sample 2), identify details of components or parts (heart and lung diagram in Sample 1, atom in Sample 6), or introduce specific data to be compared, reported, or used in understanding the concept (bar chart in Sample 3, angles on a survey math assessment question in Sample 5)?
- How do different accessibility modalities convey this information? A relatively simple bar chart or line graph can be understood when described and conveyed with a reading tool (bar chart in Sample 3). A more complex image may require a tactile graphic for a braille reader (heart and lung diagram in sample 1).
- What is the age, grade level, and disability of the student who needs this information? For example, students experienced in using screen readers or text-to-speech software probably have the skills to navigate a table. However, younger students will not likely use screen readers yet and will not have experience reading images converted to tables. Information presented in a list will be more accessible for younger students (map in Sample 2).
- What prior knowledge can reasonably be expected of the student? In a description of a secondary math graphed equation, the reader is expected to have basic knowledge of the layout of the graph and readily recognize the image described (functions and graphs in Sample 4). An older student will most likely have an idea of the general location of states on a map of the United States, but a younger student may need the names of the states identified in a description or in a tactile graphic (map in Sample 2).
The answers to these questions will help identify the modality to use in a particular situation. However, even experts with different backgrounds and experience have different opinions about what makes an image accessible. There is seldom a definitive answer because an image that is accessible for one student is not necessarily accessible for other students.
Even when a good alternative is identified, the technical requirements for creating that alternative are not always clear. For example, even if a publisher creates a file in the appropriate format for creating a 3D object or a tactile graphic, the user must have the technical knowledge necessary to turn that file into the desired result, as well as access to specialized equipment such as a 3D printer or embosser. Even the relatively simple addition of a text description in a book can raise technical questions.
This digital book is a collection of sample accessible images developed by the DIAGRAM Center. These samples will provide different types of image alternatives that can be used in a variety of academic disciplines and for varying grade levels. Importantly, the sample book provides real-world examples of both the accessible image and the underlying code used to produce it. That is, it provides content samples as well as technical samples. The code samples are provided for DAISY (Digital Accessible Information System) and EPUB 3. The DAISY standard defines the format and content of a digital talking book (DTB). DTBs are designed to make print material accessible and navigable for blind or otherwise print-disabled persons. EPUB 3 is the latest release of the EPUB standard, which is the most widely adopted format for mainstream digital books (eBooks). Our intention is that this sample book will serve as an exemplar for creating accessible digital images.
The DIAGRAM Center is engaged in developing and supplying technical standards, free tools, and training to help educational media producers create or obtain image alternatives and publish them within or alongside their digital content. Our mission is to make it easier, faster, and cheaper to create and use accessible digital images. This book serves as introduction to the work that the DIAGRAM Center and its community of educators and content creators make possible.