Image Alt tag

[Perkin]

If an image is missing an img alt tag is supposed to be displayed instead of the image, but it's not getting displayed if the image is missing, is there any way to 'turn it on' ?

Say the html is as follows:

<img alt="Chapter 1"  src="../Images/ch01.jpg" title="Chapter 1" />

If the image is available, it display all well and good, but if I do a stripped down version, removing all the images (leaving code the same - I know I'll probably get validation errors, but should still work), the alt tag should be displayed in its place.

I would like to get it to do so without having to go through and recode all the image tags.

[Keroberos]

I think whether the alt attribute displays or not is up to the reader software. According the ePub spec, the alt tag may be used by the reader (as opposed to must), which means it's another thing in the spec that is optional so may or may not be supported. As an alternative, you could try the title attribute (although that's optional too).

[JSWolf]

The thing is, why do we need an alt tag? If the ePub is built properly, the image will be there anyway and display.

[Jellby]

In a well-designed reader, you'd be able to enable/disable images and get the image or the alt text... But I know of no reader like this, and probably most readers will just show blank (or crash) if an image file is missing.

[Perkin]

A friend has got a college textbook which has a lot of superfluous pics for fancy text (especially chapter/section headings) which I was hoping could easily be trimmed, but still leave the caption/title as a guide to what it was - there's loads and a few are quite large filesize wise for what's actuall being displayed. In a browser it would be all well and good, but on a handheld reader is just silly.

I'll just run a search and replace and change the img tags to just display whatever is in the alt tag as a span with a class in which fontsize is doubled, then safely remove the images.

On my Sony any missing images are just ignored, and don't display anything, at least it doesn't crash.

[Jellby]

Originally Posted by JSWolf

The thing is, why do we need an alt tag? If the ePub is built properly, the image will be there anyway and display/

Just how is the image displayed in a text-to-speech system?

And a user may choose not to display images.

[theducks]

Originally Posted by JSWolf

The thing is, why do we need an alt tag? If the ePub is built properly, the image will be there anyway and display/

People do use TTS from time to time for various reason including Poor Vision.
The Alt Tag is read by the speech software and should contain a short summary of the image. ie 'Publisher Logo'

[Jellby]

That said, it is perfectly legal to have a blank alt tag (alt=""), and it is recommended when the image is purely decorative and does not need any explanation. The alt tag should not be a duplicate or a replacement of a caption.

[FunkeXMix]

Here's couple of annoying requirements from the newest edition of iBookStore Asset Guide 5.1.

For accessibility , the alt attribute for an image must be included; the value must be an appropriate replacement for the image. It should just be what you would have put in the prose if the image was not included , as shown in the following example:

<p>The hillside was covered in poppies.
<img src="images/page1/flowers.jpeg" alt="The poppies are red, orange, and
yellow, and a winding path leads to a house.">
A dog was asleep on the porch.</p>

The following example is not as effective; the alt text only describes the image, instead of being a textual replacement for the image. When reading without the image, the text does not flow as well as the example above.

<p>The hillside was covered in poppies. <img src="images/page1/flowers.jpeg"
alt="A bunch of poppies and a house."> A dog was asleep on the porch.</p>

The following alt attributes are not acceptable: alt="none", alt="nothing", alt="image", or
alt="page 3". Leaving out the alt attribute is also not acceptable. The attribute alt="" is acceptable in cases where the image is decorative and does not have any content or meaning

Personally I wish this was not necessary for iBooks publishing. I mean, if you make a fashion type eBook with lots of images. Visually impaired readers who need alt tags are not even consumers of this type of eBook.

It's just a pointless time consuming addition to the production flow for some type of eBooks.

[JSWolf]

I was just looking at Eye of the World in getting it ready for reading. The maps you cannot have an appropriate alt for it. There are other graphics that are just decorations so alt tags should be removed. Apple is losing the plot and going over the deep end here.

[Jellby]

Originally Posted by FunkeXMix

Personally I wish this was not necessary for iBooks publishing. I mean, if you make a fashion type eBook with lots of images. Visually impaired readers who need alt tags are not even consumers of this type of eBook.

It's just a pointless time consuming addition to the production flow for some type of eBooks.

It's not an iBooks requirement, it's an XHTML requirement, and ePub requires (sort of) valid XHTML.

As I said above, and as you repeat in your post, alt="" is perfectly valid and recommended in decorative images. But sometimes images are not just decorative, they may be a sample of hand-written text, a strange symbol, or even an illustration that's closely linked to the text ("and this is what he found when he opened the door: [here comes an illustration]"). For those cases you need to provide something meaningful in the alt attribute. For the rest, just use alt="". Apple is not requiring anything new, but they may be providing bad examples.

[eschwartz]

Originally Posted by Jellby

As I said above, and as you repeat in your post, alt="" is perfectly valid and recommended in decorative images. But sometimes images are not just decorative, they may be a sample of hand-written text, a strange symbol, or even an illustration that's closely linked to the text ("and this is what he found when he opened the door: [here comes an illustration]"). For those cases you need to provide something meaningful in the alt attribute. For the rest, just use alt="". Apple is not requiring anything new, but they may be providing bad examples.

In such cases, I believe the alt tag is what allows the text that is shown in image form to become searchable. Very important in a book that uses, for example, pictures of a sign, or handwritten notes, which cannot be coded as plain text and an image is used instead. If it is important to the book, people searching for it will fail to find it -- unless an alt tag gives the text to the search engine of the ereader.

[JSWolf]

A handwritten note can be rendered with an embedded handwriting font.