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Re: [whatwg] canvas drawImage and EXIF orientation metadata

From: Glenn Maynard <glenn@zewt.org>
Date: Thu, 17 Apr 2014 09:30:21 -0500
Message-ID: <CABirCh8AipxyJnt0PiPj=qAY58T+8Msm8a09JUPV7cUTvL4cBA@mail.gmail.com>
To: Jonas Sicking <jonas@sicking.cc>
Cc: Justin Novosad <junov@google.com>, whatwg <whatwg@lists.whatwg.org>, Boris Zbarsky <bzbarsky@mit.edu>
On Thu, Apr 17, 2014 at 2:46 AM, Jonas Sicking <jonas@sicking.cc> wrote:

> The problem here stemms from that orientation data lives as "metadata"
> in the EXIF data of image formats. This means that many tools has
> simply ignored that metadata.
>
> The result seems to have been that people open their images in tools
> that ignore the EXIF metadata. Then rotates the pixel data using that
> tool. Then saves the image again while keeping the EXIF metadata
> unchanged.
>
> This now means the pixels have been rotated (say) 90 degrees, but the
> EXIF metadata still says "rotate image 90 degrees". So any tool that
> now honors the EXIF renders the picture *wrong*.
>
> So effectively the EXIF metadata has to be ignored in order to keep
> webcompat. That was the case even before image-orientation was
> implemented.
>
> FWIW I believe that WebP is remaking this same mistake. Would be cool
> if someone tried to prevent this from happening.
>

The question was "why is this a CSS style instead of a property on <img>",
not "why isn't this just the default".

-- 
Glenn Maynard
Received on Thursday, 17 April 2014 14:30:46 UTC

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