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Differences in jpg lossless rotate freeware

 
 
MsOsWin@anon.com
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      01-06-2005
I rotated the same original photo using "lossless" rotation feature of each of these:
Fotoview, IrfanView (Jpeg_transform plugin), and Faststone.

The 3 resulting files all appear the same when viewed in all of those apps and when
viewed in IE6, Firefox 1.0, and WinXP's viewer (shimgvw). However resulting files look
*different* when viewed in thumbnail view of WinXP. Also, filesizes differ a little:


Photo view in XP thumb filesize kb

IMG_1342.jpg = Orig (compare to this) 765
FastoneRotat1342.jpg slightly sharper 764
FotoviewRotat1342.jpg dotted 765
IrfanviewRotat1342.jpg equally (?)smooth 751


Here are the files. "th" versions are thumbnail versions:


Original:
http://img160.exs.cx/img160/6933/img13425rf.th.jpg
http://img160.exs.cx/img160/6933/img13425rf.jpg

Fastone
http://img55.exs.cx/img55/7285/fasto...13428yo.th.jpg
http://img55.exs.cx/img55/7285/fastonerotat13428yo.jpg

Fotoview
http://img146.exs.cx/img146/4803/fot...13420ov.th.jpg
http://img146.exs.cx/img146/4803/fot...tat13420ov.jpg

IrfanView
http://img75.exs.cx/img75/8983/ifran...13424sj.th.jpg
http://img75.exs.cx/img75/8983/ifran...tat13424sj.jpg

Does anyone have any theories as to why the differences? I'd choose IrfanView, but I
also need lossless cropping and IrfanView Jpeg_transform lacks lossless crop.
 
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Mike
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      01-06-2005
Simple solution: save the original JPG in TIFF or another lossless
format, and crop/save as JPG from there.

<(E-Mail Removed)> wrote in message news:Xns95D636EAAC6DMsOsWinAnon@64.85.239.19...
> I rotated the same original photo using "lossless" rotation feature of each of these:
> Fotoview, IrfanView (Jpeg_transform plugin), and Faststone.
>
> The 3 resulting files all appear the same when viewed in all of those apps and when
> viewed in IE6, Firefox 1.0, and WinXP's viewer (shimgvw). However resulting files look
> *different* when viewed in thumbnail view of WinXP. Also, filesizes differ a little:
>
>
> Photo view in XP thumb filesize kb
>
> IMG_1342.jpg = Orig (compare to this) 765
> FastoneRotat1342.jpg slightly sharper 764
> FotoviewRotat1342.jpg dotted 765
> IrfanviewRotat1342.jpg equally (?)smooth 751
>
>
> Here are the files. "th" versions are thumbnail versions:
>
>
> Original:
> http://img160.exs.cx/img160/6933/img13425rf.th.jpg
> http://img160.exs.cx/img160/6933/img13425rf.jpg
>
> Fastone
> http://img55.exs.cx/img55/7285/fasto...13428yo.th.jpg
> http://img55.exs.cx/img55/7285/fastonerotat13428yo.jpg
>
> Fotoview
> http://img146.exs.cx/img146/4803/fot...13420ov.th.jpg
> http://img146.exs.cx/img146/4803/fot...tat13420ov.jpg
>
> IrfanView
> http://img75.exs.cx/img75/8983/ifran...13424sj.th.jpg
> http://img75.exs.cx/img75/8983/ifran...tat13424sj.jpg
>
> Does anyone have any theories as to why the differences? I'd choose IrfanView, but I
> also need lossless cropping and IrfanView Jpeg_transform lacks lossless crop.



 
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Steve Wolfe
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      01-06-2005
> I rotated the same original photo using "lossless" rotation feature of
each of these:
> Fotoview, IrfanView (Jpeg_transform plugin), and Faststone.
>
> The 3 resulting files all appear the same when viewed in all of those apps

and when
> viewed in IE6, Firefox 1.0, and WinXP's viewer (shimgvw). However

resulting files look
> *different* when viewed in thumbnail view of WinXP. Also, filesizes differ

a little:

I saved all four images, opened them in photoshop, rotated the original,
and pasted the various rotations of yours overtop with the layer set to
"difference", even at 800% magnification, I saw nothing but black.
Flattening the image, then turning the contrast up to 99 produced a couple
of odd pixels in each one - but the difference is so miniscule that they
might as well not even be there.

As to why the thumbnails would look different, I can't say, but it is
probably a flaw or weakness in XP's thumbnail generation and/or caching.

steve


 
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Toke Eskildsen
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      01-06-2005
http://www.velocityreviews.com/forums/(E-Mail Removed) wrote:

> I rotated the same original photo using "lossless" rotation
> feature of each of these: Fotoview, IrfanView (Jpeg_transform
> plugin), and Faststone.
>
> The 3 resulting files all appear the same when viewed in all of
> those apps and when viewed in IE6, Firefox 1.0, and WinXP's viewer
> (shimgvw).


They pixels are the same. If you convert the files to BMP and compare
them, you'll see that they are identical down to the last bit.

> However resulting files look *different* when viewed in thumbnail
> view of WinXP.


That's because XP displays the thumbnails embedded in the JPEGs.
Apparently the three utilities uses different methods for creation of
the embedded thumbnails.

If you don't like that, you can use a tool like jhead to remove the
embedded thumbnails. Note that this will slow down previewing.
 
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Toke Eskildsen
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      01-06-2005
Mike wrote:

> Simple solution: save the original JPG in TIFF or another lossless
> format, and crop/save as JPG from there.


By using your method, an additional JPEG compression with resulting
artifacts would be introduced, while the lossless scenario avoids this.
 
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MsOsWin@anon.com
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      01-06-2005
"Steve Wolfe" <(E-Mail Removed)> in news:(E-Mail Removed):


> I saved all four images, opened them in photoshop, rotated the
> original,
> and pasted the various rotations of yours overtop with the layer set
> to
>"difference", even at 800% magnification, I saw nothing but black.
> Flattening the image, then turning the contrast up to 99 produced a
> couple of odd pixels in each one - but the difference is so miniscule
> that they might as well not even be there.


Ah, thanks for pursuing a comparison I was unaware is possible.

since Irfan produced smallest kb, I wondered if Irfan 'optimized' non visual data out of
existence. but during lossless rotates, i chose transform Options that saved info. And,
file Properties showed the text data retained.

i didn't check whether any of the other apps might have deleted EXIF type data.

> As to why the thumbnails would look different, I can't say, but it
> is
> probably a flaw or weakness in XP's thumbnail generation and/or
> caching.


the flaw seems to be consistent in that files cropped by Fotoview are 'dotty' looking (in
XP thumb view), while Irfan's are smooth. (I discovered this only because I saw this
obvious difference within a folder of both Irfan and Fotoview files.)


 
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MsOsWin@anon.com
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      01-06-2005
Toke Eskildsen <(E-Mail Removed)> in news:Xns95D66537D6327tokeeskildsen@
130.133.1.4:


> They pixels are the same. If you convert the files to BMP and compare
> them, you'll see that they are identical down to the last bit.
>
>> However resulting files look *different* when viewed in thumbnail view
>> of WinXP.

>
> That's because XP displays the thumbnails embedded in the JPEGs.
> Apparently the three utilities uses different methods for creation of
> the embedded thumbnails.


aha!
now i recall reading about that internal thumbnail 'feature' in digicam file creation.

> If you don't like that, you can use a tool like jhead to remove the
> embedded thumbnails.


also creating slightly smaller images for web browsers.

> Note that this will slow down previewing.


and presumably xp thumbs would be forced to create identical thumbs.

noting your other response regarding tiff >> jpg loss, i'll probably keep using the
lossless transforms, since in this case, i'm not picky about *precision* crop or rotation.

thanks for all replies.


 
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Keith Sheppard
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      01-06-2005
>>Apparently the three utilities uses different methods for creation of
>>the embedded thumbnails.


I can think of three ways an application might go about this. The embedded
thumbnail is, itself, jpeg encoded so you could:

1. Perform lossless rotation of the thumbnail jpeg.

2. Perform bitwise rotation of the thumbnail and re-encode.

3. Create a new thumbnail from the rotated main image.

In my own application I used option 3 because it was the easiest. It means
that the new thumbnail may not be a precise rotation of the original
thumbnail but the quality should be equivalent. Mind you, I am not
convinced that option 1 is any better. The original thumbnail was
(presumably) created by reducing and encoding the original image so there's
no reason to suppose that rotating it will produce better results than
repeating the reduce/encode process on an identical but rotated image.

Option 2 is the worst because it implies progressive degradation of the
thumbnail image with each rotation.

Keith


 
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Colin D
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      01-06-2005


"(E-Mail Removed)" wrote:
>
> I rotated the same original photo using "lossless" rotation feature of each of these:
> Fotoview, IrfanView (Jpeg_transform plugin), and Faststone.
>
> The 3 resulting files all appear the same when viewed in all of those apps and when
> viewed in IE6, Firefox 1.0, and WinXP's viewer (shimgvw). However resulting files look
> *different* when viewed in thumbnail view of WinXP. Also, filesizes differ a little:
>
> Photo view in XP thumb filesize kb
>
> IMG_1342.jpg = Orig (compare to this) 765
> FastoneRotat1342.jpg slightly sharper 764
> FotoviewRotat1342.jpg dotted 765
> IrfanviewRotat1342.jpg equally (?)smooth 751
>
> Here are the files. "th" versions are thumbnail versions:
>
> Original:
> http://img160.exs.cx/img160/6933/img13425rf.th.jpg
> http://img160.exs.cx/img160/6933/img13425rf.jpg
>
> Fastone
> http://img55.exs.cx/img55/7285/fasto...13428yo.th.jpg
> http://img55.exs.cx/img55/7285/fastonerotat13428yo.jpg
>
> Fotoview
> http://img146.exs.cx/img146/4803/fot...13420ov.th.jpg
> http://img146.exs.cx/img146/4803/fot...tat13420ov.jpg
>
> IrfanView
> http://img75.exs.cx/img75/8983/ifran...13424sj.th.jpg
> http://img75.exs.cx/img75/8983/ifran...tat13424sj.jpg
>
> Does anyone have any theories as to why the differences? I'd choose IrfanView, but I
> also need lossless cropping and IrfanView Jpeg_transform lacks lossless crop.


I get a different file size than your table above when I right click on
the image and look at file info. Here is your table with the sizes I
obtained:

> IMG_1342.jpg = Orig (compare to this) 782,972
> FastoneRotat1342.jpg slightly sharper 781,865
> FotoviewRotat1342.jpg dotted 783,192
> IrfanviewRotat1342.jpg equally (?)smooth 768,903


Can't say at this point whether the varying sizes are due to algorithmic
differences or due to the rotation. However, since ordinary jpeg
compression uses a 16 x 16 matrix of pixels, for lossless rotation the
image dimensions need to divide evenly by 16 - which your 1600 x 1200
pixel images will do (this can be a problem if you crop and re-save with
non-divisible dimensions). So, I guess that the differences are indeed
due to different algorithms being used. I presume you used the same
compression level on each image.

Colin
 
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Alfred Molon
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      01-06-2005
In article <41DD13FB.20702914@killspam.127.0.0.1>, Colin D says...

> Can't say at this point whether the varying sizes are due to algorithmic
> differences or due to the rotation. However, since ordinary jpeg
> compression uses a 16 x 16 matrix of pixels,


Should be 8x8 unless they changed something.
--

Alfred Molon
------------------------------
http://groups.yahoo.com/group/Olympus_405080/
Olympus 5060 resource - http://myolympus.org/5060/
Olympus 8080 resource - http://myolympus.org/8080/
 
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