Re: irfanview lossless jpg rotation

"Don Wiss" <donwiss@no_spam.com> wrote in message
news:vuaeh2tkvs42fs0ebl72cf9umhm3es6of6@4ax.com...
> On Sun, 24 Sep 2006 16:11:28 -0700, Paul Lutus <nospam@nosite.zzz> wrote:
>
>>dohduhdah@yahoo.com wrote:
>>> When I try to use irfanview to rotate jpg pics with lossless jpg
>>> operations, I notice that the filesize
>>> changes. When I do lossless rotations in ACDSee, I notice the filesize
>>> stays identical.
>>> Is there any way to rotate pics with irfanview that will yield an
>>> identical filesize for the rotated jpg?
>>
>>By definition, rotated JPG files should not be the same size, except by
>>pure
>>chance. Because JPG is a lossy compression method, this should not be
>>expected.
>
> Wrong. The thread is about lossless jpg rotation. The file is not
> decompressed and recompressed. It is rotated without changing the
> compression.
>
> I just rotated a file 90 degrees losslessly in IrfanView. It went from
> 636,930 bytes to 630,305 bytes. I rotated it back, going in 90 degree
> increments three times. Now it is 631,432, though it is the same
> orientation as it started.
>
> I just tried jpegcrop. It also rotates losslessly. I started with the
> orginal file again. To summarize:
>
> Original: 636,930 bytes
> 180 flip: 636,982
> 90 left:  635,768
> 90 right: 635,726

irfan might be able to shed some light on this...
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