Image EXIF Orientation Bug – or Feature? | Hacker News Reader

Image EXIF Orientation Bug – or Feature?

blog.praveen.science

>I’ve found the results strange in Safari and Chrome, since there’s this CSS property for <img />, image-orientation, and with it one can say to use the EXIF declared on the photo metadata to fix the orientation. The default value is 0deg. If you want show the image with the correct orientation, the value must be from-image.

I went to the linked specification (https://www.w3.org/TR/css3-images/#image-orientation) and "from-image" is not specified here as a possible value of "image-orientation".

It was in CSS 4 at some point:

https://www.w3.org/TR/2012/WD-css4-images-20120911/#the-imag...

It seems that Firefox from-image is nonstandard (from-image in specification is only defined for image-resolution). And default behavior of ignoring EXIF rotation seems correct according to this weird specification:

>Note that some devices will "tag" an image with some metadata indicating its correct orientation, so image viewing software can do the necessary transformation themselves. Due to legacy compatibility restraints, Web browsers are required to ignore this data by default. A future level of this specification is expected to have a value that applies the metadata-specified transformation automatically.

IMO EXIF rotation should be applied always, and any CSS rotations should combine with it, not override.

> IMO EXIF rotation should be applied always, and any CSS rotations should combine with it, not override.

I agree. EXIF rotation is a part of the image and it's just an implementation detail of the image data. Browsers shouldn't leak this.

Presumably the issue is "Given that browsers that ignore EXIF rotation already exist, should modern browsers display the same page differently?"

Yes because it will fix more pages than it will break.

But what about the compatibility, graceful degradation, etc. of the browsers that yet don't support this feature? Won't that break everything else?

https://drafts.csswg.org/css-images-3/#propdef-image-orienta...

But it has been dropped from the next version which states:

> If the image has an orientation specified in its metadata, such as EXIF, the UA must rotate or flip the image to correctly orient it as the metadata specifies.

That statement appears to only apply to images created with the CSS image() function, not HTML <img>s.

The exiftran utility can strip the EXIF orientation tag and apply the rotation losslessly to the image. Looks like it worth doing it. AFAIK imagemagick reencodes the image.

Correct conclusion, strip the info. EXIF is a mess on the web, thankfully Digikam easily normalizes all of my photos with simple batch process. Not my videos though.

Most of the online upload services do it. Like Imgur strips these information. :)

One thing I one day want to try is to include some unique search terms in an image EXIF description to see if Googlebot picks it up in a way that is subsequently searchable.

As for Wordpress people using third party services to remove bloat from images in a paid for, tediously manual way - don't! Configure your server to do it with Google's mod_pagespeed. You can serve src_set images whilst you are at it that way making the web quicker and more eco friendly.

Or just load the image into GIMP and make use of its nifty image optimisation while saving it again.

(Oh, and feature. Definitely feature.)

Wow. You mean to say, the server can strip it off while serving the images?

To fix these:

    convert -auto-orient in.jpg out.jpg

A note for clueless windows users:

    convert /?
    Converts a FAT volume to NTFS.
    
    CONVERT volume /FS:NTFS [/V] [/CvtArea:filename] [/NoSecurity] [/X]
    
    
      volume      Specifies the drive letter (followed by a colon),
                  mount point, or volume name.
      /FS:NTFS    Specifies that the volume will be converted to NTFS.
      /V          Specifies that Convert will be run in verbose mode.
      /CvtArea:filename
                  Specifies a contiguous file in the root directory
                  that will be the place holder for NTFS system files.
      /NoSecurity Specifies that the security settings on the converted
                  files and directories allow access by all users.
      /X          Forces the volume to dismount first if necessary.
                  All open handles to the volume will not be valid.

You probably can't do any damage attempting to use it to convert images, but there might be a way to screw up attempting to convert an image so badly you destroy your filesystem.

Exactly, this command is for converting a file system and not an image or a single file.

It's unfortunate that ImageMagick decided to call their primary command "convert".

Don't do that, it will degrade the image quality. Use exiftran instead as it will do lossless rotation.

Quick questions regarding this:

1. Will this work without having to install new software on Windows, Mac, Linux?

2. Will this degrade image quality?

1. This uses the Image Magick command "convert" so it will work on any system that has it installed. I've only used it on Mac and Linux.

2. It isn't lossless, no. I think jpegtran can do this, but you'll need to first read the correct orientation out of the EXIF data and then give the right arguments to jpegtran. Since the loss in quality is tiny, I just use -auto-orient.

Ah thanks. :)

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