Newbie: JPG puzzle?

Is there any way I can keeep jpg file at the same size?

This is any 170K jpg. All I did was to have flipped it horizontally
.. It then saved as a 340K file at 100%.

I thought, for flipping, the software only re-arranged the pixels.
What can i do if I want to keep jpg at small size?

does it mean only the original JPG is the smallest?

ABC
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ABC wrote:

Is there any way I can keeep jpg file at the same size?

This is any 170K jpg. All I did was to have flipped it horizontally
. It then saved as a 340K file at 100%.

I thought, for flipping, the software only re-arranged the pixels.
What can i do if I want to keep jpg at small size?

does it mean only the original JPG is the smallest?

ABC
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100% is a bit excessive. 95% is fine.

If it's not been cropped, you can rotate without any change using
irfanview or most any newer program.

If you do use the
lossless rotation commands, the file size changes *very* little (I
don't understand why it changes *at all*, but in my experience it
does; but only very little, like 1% or something).

When you do lossless rotation, the encoded image will normally be the same
size as the original, but there's more than that in a jpg file.

There's also a great deal of header information containing camera settings,
maybe a thumbnail image, and other stuff. The software writing a jpg has a
great deal of flexibility when it comes to the format of this header
information. The reason the file size changes is that the saving software
probably uses a different header layout (even though it saves the same
information) from whatever saved the original (probably a camera).

In my experience, cameras tend to use inefficient header layouts. I presume
the firmware writers were prepared to sacrifice a few bytes of file size to
keep the firmware simple. That's legitimate because they probably have to
fit their code into a limited amount of memory.

With my own home-made photo application I can open an image from my camera
and save it again without re-encoding (ie. no quality loss) and almost
invariably end up with a smaller file than the camera managed (and yes, my
software can also do lossless rotation).

Keith
(free PhotoMan download from
http://homepages.tesco.net/~Keith.Sh...toman/home.htm)

On Tue, 15 Mar 2005 17:26:12 -0800, paul wrote:


100% is a bit excessive. 95% is fine.

If it's not been cropped, you can rotate without any change using
irfanview or most any newer program.

I am using Irfanview!
Open any JPG. flip it and click 'save'. It will open a dialog box
suggesting 85% quality. Set it to 100% and I end up with a bigger
file.

ABC

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On Tue, 15 Mar 2005 19:53:00 -0600, David Dyer-Bennet
wrote:

What software did you use, and what exact command? Ordinary
photo-editing software doesn't support the lossless rotation
capabilities mostly; that's mostly supported in viewing and organizing
software (like Irfan View and Thumbs Plus). If you do use the
lossless rotation commands, the file size changes *very* little (I
don't understand why it changes *at all*, but in my experience it
does; but only very little, like 1% or something).

I tried both in Irfanview and Photoimpact. Once you rotate the image
and save, it will be bigger, much bigger.

ABC

Please do not reply by email.Reply to NG

On Wed, 16 Mar 2005 22:30:33 +0800, ABC wrote:

On Tue, 15 Mar 2005 19:53:00 -0600, David Dyer-Bennet
wrote:

What software did you use, and what exact command? Ordinary
photo-editing software doesn't support the lossless rotation
capabilities mostly; that's mostly supported in viewing and organizing
software (like Irfan View and Thumbs Plus). If you do use the
lossless rotation commands, the file size changes *very* little (I
don't understand why it changes *at all*, but in my experience it
does; but only very little, like 1% or something).

I tried both in Irfanview and Photoimpact. Once you rotate the image
and save, it will be bigger, much bigger.

ABC

Do a little experimentation.
You're saving at 100%. Try lower values, and see what the file size
is, and if there's any degradation that you will notice.

--
Bill Funk
Change "g" to "a"

ABC writes:

On Tue, 15 Mar 2005 19:53:00 -0600, David Dyer-Bennet
wrote:

What software did you use, and what exact command? Ordinary
photo-editing software doesn't support the lossless rotation
capabilities mostly; that's mostly supported in viewing and organizing
software (like Irfan View and Thumbs Plus). If you do use the
lossless rotation commands, the file size changes *very* little (I
don't understand why it changes *at all*, but in my experience it
does; but only very little, like 1% or something).

I tried both in Irfanview and Photoimpact. Once you rotate the image
and save, it will be bigger, much bigger.

I just grabbed random image, checked its size (43.9k), viewed it in
Irfanview, selected "jpg lossless operations" and then 90 degrees
clockwise, let it run, closed the file. Checked the file size
(unchanged), and viewed the file again, and I'm viewing the rotated
version.

I believe your mistake is in viewing the image, and then saving it.
The lossless jpeg plugin in irfanview modifies the file directly; when
you save after that, you're re-compressing, which introduces new
artifacts and may depending on the compression setting change the file
size as well.
--
David Dyer-Bennet, , http://www.dd-b.net/dd-b/
RKBA: http://noguns-nomoney.com/ http://www.dd-b.net/carry/
Pics: http://dd-b.lighthunters.net/ http://www.dd-b.net/dd-b/SnapshotAlbum/
Dragaera/Steven Brust: http://dragaera.info/

(Dave Martindale) writes:

David Dyer-Bennet writes:

What software did you use, and what exact command? Ordinary
photo-editing software doesn't support the lossless rotation
capabilities mostly; that's mostly supported in viewing and organizing
software (like Irfan View and Thumbs Plus). If you do use the
lossless rotation commands, the file size changes *very* little (I
don't understand why it changes *at all*, but in my experience it
does; but only very little, like 1% or something).

That's probably because lossless JPEG rotation is not just moving DCT
coefficients around. It has to undo the (lossless) Huffmann compression,
then move the DCT coefficients around, then re-do the Huffmann
compression. No information is lost, but you *are* re-encoding the
data using Huffmann in a different order which can give a slightly
different compressed size. You might also be doing 2-pass Huffmann after
the rotation while the camera only did 1-pass Huffmann.

Thanks, never looked at the spec details myself. So that makes sense
then.
--
David Dyer-Bennet, , http://www.dd-b.net/dd-b/
RKBA: http://noguns-nomoney.com/ http://www.dd-b.net/carry/
Pics: http://dd-b.lighthunters.net/ http://www.dd-b.net/dd-b/SnapshotAlbum/
Dragaera/Steven Brust: http://dragaera.info/

On Wed, 16 Mar 2005 18:32:04 -0600, David Dyer-Bennet
wrotd:

I just grabbed random image, checked its size (43.9k), viewed it in
Irfanview, selected "jpg lossless operations" and then 90 degrees
clockwise, let it run, closed the file. Checked the file size
(unchanged), and viewed the file again, and I'm viewing the rotated
version.
Got that.

This is better Photimpact( and I bet PS,too). Photoimpact does not
offer lossless and same-file-size rotation. Why?



ABC
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