show jpeg-kompression

MS
Posted By
manuel_s
Feb 21, 2008
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362
Replies
7
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Closed
Hi!
Is it possible to see what kompression-settings were made when a jpeg was saved? When Saving you get that 0-100%-Slider. When I save an image with for ex. 60%, can I find out wheather it was 60% or 70% after saving?
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DM
dave_milbut
Feb 21, 2008
Is it possible to see what kompression-settings were made when a jpeg was saved?

nope.

When Saving you get that 0-100%-Slider. When I save an image with for ex. 60%, can I find out wheather it was 60% or 70% after saving?

what if the saving app didn’t use 0-100% what if it used 1-10? or some other range (0-300)?

bottom line. no, you can’t tell. once it’s saved it’s saved. that data isn’t retained anywhere.
MS
manuel_s
Feb 21, 2008
Ok, thanks, good to know…
I
ID._Awe
Feb 21, 2008
to add to wat dave said, the compression is relevant to the image.
GH
Gernot_Hoffmann
Feb 21, 2008
Nobody knows the ‘settings’, but one can draw
some conclusions:
1. the compression ratio Oldfilesize/Newfilesize
for somewhat average photos:
5..10 optimal quality
20..30 average quality
40 rather bad quality
2. accessible only for programmers: the content
of the so-called quantization tables

The program Quite a Box of Tricks by
<http://www.quite.com>
delivers quality/compression comments for JPEGs
in PDFs.
Such an information is very helpful for analyzing
the compression state: resolution in ppi, kind of
color space, kind of compression, for JPEGs: which
quality.

Best regards –Gernot Hoffmann
P
Pipkin
Feb 21, 2008
That’s not bad: jpgQ – JPEG Quality Estimator (freeware) – <http://www.mediachance.com/digicam/jpgq.htm>
MS
manuel_s
Feb 22, 2008
Cool, many thanks…
DM
dave_milbut
Feb 22, 2008
from that site:

Loss is adding up but not as many people think – if we use twice 75% first time then 75% second time it doesn’t mean that the second round is equal to 55% of original quality (75% of first 75%). There is some loss but far less. So it doesn’t work like your taxes.

as far as i know from what i’ve read, it does indeed give you 75% of quality EACH time you save. so with an assumption that flawed (assuming that i’m right, which is not always true <g>), how will his software "estimate" anything correctly?

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