Can I check something with you guys

On Tue, 27 Nov 2007 22:18:28 -0700, Norm DePlume wrote:

On Tue, 27 Nov 2007 22:22:59 -0500, Andrew Kalten
In addition, IMG_6297 copy.jpg contained 30,172 bytes of extraneous
data, compared with warbirdz_12327.jpg, which contained only 79 such
bytes, as determined by comparing file sizes before and after processing
with jStrip v3.3. And, actually, there are any number of Windows
compatible graphics programs that can accomplish this task easily, but
no, they do not ship with Windows. As to whether the difference is
beyond perception, I am not prepared to state such a conclusion so
definitively.

I had no time to do a statistical analysis of the difference file,
but a quick glance using a histogram tool showed that the average
difference in luminosity was about 3-4 (out of a maximum of 255).
Since the threshold for the detection of luminosity differences
by the human eye is about one percent, this difference will just
barely exceed that level. Looking at the difference image, a vague
area of greyness is just barely discernible.

But this difference is at the lower end of the luminosity scale.
In the actual image, the differences occur in much brighter areas
where the eye is less sensitive to change and such differences are
very apt to go completely unnoticed.

So unless you are very deliberately and very intently looking for
some small difference, the images will be identical.

AK

Hello,
I agree with you that such differences are, as you said, "very apt" to
go unnoticed, although I suspect there are some who would notice. I am
reluctant to use absolutes in cyber conversations, as they are
frequently considered provocative.

On Wed, 28 Nov 2007 00:06:59 -0700, Norm DePlume wrote:

Hello,
I agree with you that such differences are, as you said, "very apt" to
go unnoticed, although I suspect there are some who would notice. I am
reluctant to use absolutes in cyber conversations, as they are
frequently considered provocative.

Human imagination can be wanton. If you present a more or less random
pattern, such as an ink blot, to the average person, he is likely to
discover many things within the meaningless form -- but such things
will have no basis in reality. That's why we always need an objective
measure.

Cyber conversations can be problematic for the same reason. If one
seeks provocation, perhaps only unconsciously, then one will tend to
discover provocation whether it exists or not.

Science is more than a white coat and a job in a laboratory. Science
is the ability to discover what really exists despite the trickery
of imagination.

AK

Glenn wrote:
http://www.warbirdz.net/largepic.php?ID=12327

The above link, when you view it, does it look identical to the image
below.
reason why I ask is on my monitor, the link above is obviously
compressed but the image below
is the same image, just not uploaded onto my website. The image i post
below, looks good and the compression is nowhere near as evident.

Yet it is the same image.
Is this glaringly obvious to you guys as well.


------------------------------------------------------------------------

Gday Glenn,

The missing bytes are the EXIF data. Any differences in compression
would be noticeable by the artifacts around any high-contrast edges (for
example, the aircraft in flight).

Regards, and thanks for wonderful images,
Pat

On 2007-11-30 04:45:13 +0100, Pat Heuvel said:

Gday Glenn,

The missing bytes are the EXIF data. Any differences in compression
would be noticeable by the artifacts around any high-contrast edges
(for example, the aircraft in flight).

Regards, and thanks for wonderful images,
Pat

Exact, there no EXIF data and no ICC profil in the picture from the web.
You can see the differences when you open the two files in the same
progam. (preview in macos X 10.4 in my example)
The newsgroup file is daker and you can see less artifacts than the web one.