- From: John Foliot <jfoliot@stanford.edu>
- Date: Thu, 21 Jan 2010 18:35:23 -0800 (PST)
- To: "'Maciej Stachowiak'" <mjs@apple.com>
- Cc: "'Matt May'" <mattmay@adobe.com>, "'HTML WG'" <public-html@w3.org>, <public-html-a11y@w3.org>
Maciej Stachowiak wrote: > > Examples: (a) read the filename, but only if it appears to > be human-readable, not a stream of random letters and numbers; (b) > perform OCR on the image, OCR these days is readily available and highly > accurate; (c) provide the contents of relevant EXIF tags. However Maciej, none of these can determine author intent, and at the end of the day if a 'page' has an image inserted using the <img> element, then it is there for a reason, and so that 'reason' needs to be expressed as part of the alternative text - there is a cognitive requirement as well that technology alone cannot deliver. If there is a consensus to expose EXIF information using an explicit attribute or element, then that's great (I personally don't think that there is a need); suggesting that somehow that data might ever be sufficient information to stand in for alt text is misleading and damaging in the longer run. Here is some sample EXIF data, taken from an actual Flickr page: Exposure: 0.017 sec (1/60) Aperture: f/3.1 Focal Length: 6.3 mm Focal Length: 6.3 mm ISO Speed: 400 Exposure Bias: +1 EV Flash: Auto, Fired File Size: 1998 kB File Type: JPEG MIME Type: image/jpeg Image Width: 2400 Image Height: 3200 Encoding Process: Baseline DCT, Huffman coding Bits Per Sample: 8 Color Components: 3 Orientation: Horizontal (normal) X-Resolution: 480 dpi Y-Resolution: 480 dpi YCbCr Positioning: Co-sited Exposure Program: Program AE Date and Time (Original): 2010:01:18 10:15:03 Date and Time (Digitized): 2010:01:18 10:15:03 Max Aperture Value: 3.1 Metering Mode: Multi-segment Light Source: Unknown Color Space: sRGB Exposure Index: 400 Sensing Method: One-chip color area Custom Rendered: Normal Exposure Mode: Manual White Balance: Auto Digital Zoom Ratio: 1 Focal Length In35mm Format: 38 mm Scene Capture Type: Standard Gain Control: High gain up Contrast: Normal Saturation: Normal Sharpness: Normal Subject Distance Range: Unknown Pentax Model Type: 2 Preview Image Size: 640x480 Preview Image Length: 38618 Preview Image Start: 15945 Date: 2010:01:18 Time: 10:15:03 Quality: Good Pentax Image Size: Unknown (255) Picture Mode: Surf & Snow; 0 Flash Mode: Auto, Fired, Red-eye reduction Focus Mode: Normal AFPoint Selected: Auto AFPoints In Focus: Top-center Focus Position: 1005 Exposure Time: 1/60 FNumber: 3.1 ISO: 400 Light Reading: 18 Exposure Compensation: +1.0 Metering Mode: Multi-segment White Balance: Auto White Balance Mode: Unknown (0) Blue Balance: 1.1953125 Red Balance: 2.1640625 Digital Zoom: 1 Saturation: Normal Contrast: Normal Sharpness: Normal DSPFirmware Version: 1.00.00.00 Image Processing: Unprocessed Data Dump: (Binary data 2540 bytes, use -b option to extract) Compression: JPEG (old-style) Orientation: Horizontal (normal) Can *ANYBODY* reading this note tell me what the picture actually is? > > I am hoping we can find a happy middle ground by giving a general > allowance for use of more information when alternative text is missing, > or in general in the face of broken content, without overselling its > capabilities. Let's turn this on its head for sake of discussion: would those who believe this is a viable point of view feel the same way if the following code: <img src="[broken path]" height="350" width="600" alt="Ford"> (and yes, this is deliberately bad alt text, but not uncommon in the wild) ...allowed UA's to invoke their magic heuristic powers to seek out another image of "Ford" that was about 350 X 600 pixels (from say Google's gadzillions of indexed images), and replaced the 'missing image' with a replacement image; do you think that the 'industry' and authors in particular would find that an acceptable solution? In many ways, that is what is being suggested here; I mean, is substituting this 'ford.jpg' image: http://www.myrddin.it/merlino/mimg/ford.jpg ...for this 'ford.jpg' image: http://www.insidesocal.com/outinhollywood/ford.jpg ...sufficient or appropriate? After all, they are both pictures of Ford... When all is said and done, no technology today (or the foreseeable future) can read minds, and so no amount of heuristic analysis can substitute for author supplied alt text that delivers author intent. > I think important considerations for that are: (1) don't > get overly specific about the type of techniques to be used, or if > examples are given, make sure they are squarely within the mainstream of > current technology; (2) make very clear that these are intended to be > emergency repair techniques, not something for authors to rely on. I think any statement that suggests futuristic magic as a potential technical possibility inside a technical specification and standard is wrong, and should be avoided. JF
Received on Friday, 22 January 2010 02:35:57 UTC