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I have been following the discussion on high contrast mode and background image sprites but I have a more basic question about inline images and HCM. For low-vision users without a screen reader on HCM, will they have difficulty seeing the inline image because it may not have sufficient contrast? Or are they expected to use a browser plugin to replace the inline image with its alt text?

I understand screen reader users will benefit because the alt text is read out? But, what about low vision users without a screen reader?

Ramya
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  • Do you talk about content images in `img` element? If so, only about transparent images? For non-transparent images there would be no contrast problem, or am I wrong? – unor Aug 28 '12 at 18:59

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For low-vision users without a screen reader on HCM, will they have difficulty seeing the inline image because it may not have sufficient contrast?

Sometimes while in High contrast mode the images change as the color is defined, so a white background on an image is turned black. I don't know if this is dependent on the image type or something else. There are a number of disabilities that involve color wash, and it would be pretty hard to cover all bases 100%. I would say it is a good idea to create images with color ratios of 4.5:1 as defined in WCAG 2.0 to cover as many bases as you can.

Or are they expected to use a browser plugin to replace the inline image with its alt text?

I don't know any that do this off hand.

Ryan B
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I am going to try to answer my own question: I think low vision users in HCM would turn off images as described here: http://kb.iu.edu/data/acpv.html#ie to show just the alt text and that's why inline images are accessible.

Ramya
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    I think you can't assume that a) _all_ low vision HCM users want to turn images off, and b) that _all_ low vision HCM users know about this setting at all. Even statistics wouldn't be of use because accessibility is about _ALL_ people with disabilites, not only a majority. – unor Aug 28 '12 at 18:53
  • I agree with unor, we cannot make any assumptions. You might have to do the best on your side to handle both the situations. There are tips to do this like using javascript to detect if HCM is enabled and Images are enabled to show hidden texts and if HCM is enabled and Images are disabled to rely on alt text. Here is such technique mentioned [detecting-if-images-are-disabled-in-browsers/](http://www.paciellogroup.com/blog/2011/10/detecting-if-images-are-disabled-in-browsers/) though its kinda buggy, you might want to fix it before using. – Ravi Kadaboina Aug 29 '12 at 02:24
  • There is a new feature in Windows 8 to detect HCM [link](http://msdn.microsoft.com/en-us/library/windows/apps/hh465764.aspx) but I don't expect it be useful until some more years when Windows 8 is adopted widely. – Ravi Kadaboina Aug 29 '12 at 02:29
  • Hmm...this explains why dojo has only text alternatives show up in HCM. The problem with having alt text show up by default in HCM is sometimes, there is just not enough real estate to show a text equivalent of every image on the page or it leads to unwieldy UI that wraps to the next line etc. – Ramya Aug 29 '12 at 15:28
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You might be interested in reading Image Sprite Technique Comparison, as there is no single best way. However I will state that assuming HCM users use or do not use images is a bad assumption. The focus should simply be on the technology: if the sprites or images are or become content, then they need to have alternate text. You can't think about them being background and unimportant when in HCM they become actual content that is modified and affects the user's ability to obtain information.

Norman B. Robins0n
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  • Thanks for the response, agree with your general observation but not sure there is a good way for this issue -- just left a comment above about real estate considerations. – Ramya Aug 29 '12 at 15:30
  • Most users aren't relying on alt text to be in layout form to read: if they are using a screen reader the text is read aloud. If they have vision, they rely on the image (even if on high magnification or in high contrast). – Norman B. Robins0n Aug 29 '12 at 18:46