Re: [Gimp-developer] JPEG lossless operations?

[Liam R E Quin]

On Thu, 2012-05-31 at 01:04 +0200, Ofnuts wrote:

> The best (and fastest) way to rotate a JPEG is to change its 
> orientation flag...

Not all programs honour the orientation flag.

Windows Explorer's thumbnails used to be an example, don't know if
that's still true in Windows 7.

Liam

-- 
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/

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Re: [Gimp-developer] JPEG lossless operations?

[Ofnuts]

On 05/30/2012 05:55 PM, Bruce wrote:
I've read that Picasa (Google's program) might be able to perform 
lossless rotations, but I'm just going by what I've read. (Source 
)


Apparently there are ways to test if the tool you use makes use of 
lossless rotation. This page lists some: 
http://www.impulseadventure.com/photo/lossless-rotation-test.html


This page also has a nice explanation of lossless rotation and its 
finer nuances:

http://www.betterjpeg.com/lossless-rotation.htm

From what I've learned so far, I think in the end you just have to 
relax about all this stuff and not worry about it too much, though it 
does help to know what's happening when you do certain things (such as 
rotate a jpeg).




The best (and fastest) way to rotate a JPEG is to change its 
orientation flag...




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Re: [Gimp-developer] JPEG lossless operations?

[Bruce]

I've read that Picasa (Google's program) might be able to perform lossless
rotations, but I'm just going by what I've read.
(Source
)

Apparently there are ways to test if the tool you use makes use of lossless
rotation. This page lists some:
http://www.impulseadventure.com/photo/lossless-rotation-test.html

This page also has a nice explanation of lossless rotation and its finer
nuances:
http://www.betterjpeg.com/lossless-rotation.htm

>From what I've learned so far, I think in the end you just have to relax
about all this stuff and not worry about it too much, though it does help
to know what's happening when you do certain things (such as rotate a
jpeg).

On Mon, May 28, 2012 at 5:31 AM, gfxuser  wrote:

> Ofnuts wrote:
>
>> On 05/27/2012 08:26 PM, gfxuser wrote:
>>
>>> Hi,
>>>
>>> reading some of the JPEG related articles here I wondered whether GIMP
>>> or GEGL can do lossless rotation and cropping on JPEG images. Can you tell
>>> me more about it?
>>>
>>> Thanks,
>>> grafxuser
>>>
>>>
>> For rotation, that would only work on images with dimensions that are a
>> multiple of 8. For cropping, that only works if you crop on 8-pixel
>> boundaries from the origin corner.
>>
>> Otherwise, this also assumes that JPEG is an "editable format", while the
>> recent kerfuffle around the Export function has demonstrated that it is
>> not, in the current vision.
>>
>>  Thanks, Ofnuts.
> Yes, 'Export vs. Save' was a long discussion and I don't want to boost it
> again. Although it takes a little getting used to I can live with the new
> behaviour. Despite of that I sometimes wondered in the past whether GIMP
> will introduce new compression artifacts if I rotated or cropped an
> existing JPEG image (yes, there are some cameras where saving in JPEG of
> sufficient quality is the best choice. Shall we not use them anymore?).
>
> Best regards,
>
> grafxuser
>
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Re: [Gimp-developer] JPEG lossless operations?

[gfxuser]

Ofnuts wrote:

On 05/27/2012 08:26 PM, gfxuser wrote:

Hi,

reading some of the JPEG related articles here I wondered whether 
GIMP or GEGL can do lossless rotation and cropping on JPEG images. 
Can you tell me more about it?


Thanks,
grafxuser



For rotation, that would only work on images with dimensions that are 
a multiple of 8. For cropping, that only works if you crop on 8-pixel 
boundaries from the origin corner.


Otherwise, this also assumes that JPEG is an "editable format", while 
the recent kerfuffle around the Export function has demonstrated that 
it is not, in the current vision.



Thanks, Ofnuts.
Yes, 'Export vs. Save' was a long discussion and I don't want to boost 
it again. Although it takes a little getting used to I can live with the 
new behaviour. Despite of that I sometimes wondered in the past whether 
GIMP will introduce new compression artifacts if I rotated or cropped an 
existing JPEG image (yes, there are some cameras where saving in JPEG of 
sufficient quality is the best choice. Shall we not use them anymore?).


Best regards,

grafxuser
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Re: [Gimp-developer] JPEG lossless operations?

[Nicolas Robidoux]

For a non GIMP solution (with severe constraints on the rotation and
cropping parameters, as is pretty much unavoidable):
http://jpegclub.org/
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Re: [Gimp-developer] JPEG lossless operations?

[Ofnuts]

On 05/27/2012 08:26 PM, gfxuser wrote:

Hi,

reading some of the JPEG related articles here I wondered whether GIMP 
or GEGL can do lossless rotation and cropping on JPEG images. Can you 
tell me more about it?


Thanks,
grafxuser



For rotation, that would only work on images with dimensions that are a 
multiple of 8. For cropping, that only works if you crop on 8-pixel 
boundaries from the origin corner.


Otherwise, this also assumes that JPEG is an "editable format", while 
the recent kerfuffle around the Export function has demonstrated that it 
is not, in the current vision.


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[Gimp-developer] JPEG lossless operations?

[gfxuser]

Hi,

reading some of the JPEG related articles here I wondered whether GIMP 
or GEGL can do lossless rotation and cropping on JPEG images. Can you 
tell me more about it?


Thanks,
grafxuser
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