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Re: Rotated image

Cross-posted to 3 groups.

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On Tue, 4 Aug 2020 at 17:35:20, Mayayana <mayayana@invalid.nospam> 
wrote:
>"J. P. Gilliver (John)" <G6JPG@255soft.uk> wrote
>
>| >Any JPG that requires software to check the
>| >orientation EXIF tags is a faulty image.
>|
>| I'm not quite sure what you're saying there: if you acknowledge the
>| _existence_ of the orientation tag (I didn't know it was part of EXIF
>| but that makes sense), then what would you consider its function?
>
>  Yes, it's part of EXIF. Bit EXIF is not universally supported
>and it's only in JPGs. There's just no reason to need that tag.
>The camera can save the image as it's taken. Instead of doing
>that they create all sorts on incompatibility. I get a lot of those
>sideways images. People don't know because they're seeing it
>on their iPhone where they took the picture. I don't understand
>why they ever would have used such an idiotic method. Whatever
>edge of the camera is up should be the top of the picture.
>
>
The reason, I presume, is that it's easier to program the camera's 
firmware to just save a flag (as part of a block of EXIF data that it's 
saving anyway), than to actually change the order of pixels written into 
the file. Originally, also, it may have reduced the need for an extra 
block of RAM to hold the image to enable any such rotation to be done; 
while memory is now probably cheap enough for that not to be as much of 
a problem (though image sizes keep growing insanely so it might still 
be!), once the practice had been established, I guess it stuck.

FWIW: when you _do_ get a "sideways image", IrfanView (might need its 
plugins, but I always install those anyway) has a "lossless rotation" 
function for JPEGs, in other words it can rotate the image without an 
extra stage of decompression/recompression and thus degradation. (It 
_doesn't_ use the orientation flag: it sets that to the top left of 
whatever you rotate to.) Other image handlers can probably do it too; 
it's easy in IV, just J enter. (That's shift-J - to bring up the JPEG 
utilities menu - and enter to repeat whatever you did last time you 
brought up that menu, which in my case is almost always a rotate.)
-- 
J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

Self Test for Paranoia:  You know you have it when you can't think of anything
that's your own fault. - "The Real Bev" in comp.mobile.android, 2019-1-1

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Rotated image Jim Scott <jim@jimXscott.co.uk> - 2020-08-03 19:19 +0100
  Re: Rotated image Andy Burns <usenet@andyburns.uk> - 2020-08-03 19:22 +0100
  Re: Rotated image nospam <nospam@nospam.invalid> - 2020-08-03 14:23 -0400
  Re: Rotated image Arlen Holder <arlenholder@newmachine.com> - 2020-08-03 18:46 +0000
    Re: Rotated image Jim Scott <jim@jimXscott.co.uk> - 2020-08-03 23:41 +0100
      Re: Rotated image nospam <nospam@nospam.invalid> - 2020-08-03 18:54 -0400
        Re: Rotated image Jim Scott <jim@jimXscott.co.uk> - 2020-08-04 00:37 +0100
  Re: Rotated image VanguardLH <V@nguard.LH> - 2020-08-03 14:19 -0500
    Re: Rotated image Arlen Holder <arlenholder@newmachine.com> - 2020-08-03 21:07 +0000
      Re: Rotated image Jim Scott <jim@jimXscott.co.uk> - 2020-08-03 23:45 +0100
        Re: Rotated image Arlen Holder <arlenholder@newmachine.com> - 2020-08-03 23:35 +0000
          Re: Rotated image Jim S <jim@jimXscott.co.uk> - 2020-08-04 00:42 +0100
            Re: Rotated image Arlen Holder <arlenholder@newmachine.com> - 2020-08-04 02:06 +0000
              Re: Rotated image Jim Scott <jim@jimXscott.co.uk> - 2020-08-04 10:04 +0100
        Re: Rotated image "J. P. Gilliver (John)" <G6JPG@255soft.uk> - 2020-08-04 02:14 +0100
          Re: Rotated image "Mayayana" <mayayana@invalid.nospam> - 2020-08-04 09:09 -0400
            Re: Rotated image nospam <nospam@nospam.invalid> - 2020-08-04 10:05 -0400
            Re: Rotated image "J. P. Gilliver (John)" <G6JPG@255soft.uk> - 2020-08-04 22:07 +0100
              Re: Rotated image "Mayayana" <mayayana@invalid.nospam> - 2020-08-04 17:35 -0400
                Re: Rotated image nospam <nospam@nospam.invalid> - 2020-08-04 18:00 -0400
                Re: Rotated image "J. P. Gilliver (John)" <G6JPG@255soft.uk> - 2020-08-04 23:18 +0100
              Re: Rotated image nospam <nospam@nospam.invalid> - 2020-08-04 18:00 -0400
  Re: Rotated image "J. P. Gilliver (John)" <G6JPG@255soft.uk> - 2020-08-04 02:24 +0100
    Re: Rotated image Arlen Holder <arlenholder@newmachine.com> - 2020-08-04 02:06 +0000

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