| Author |
Compression ratio.
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| quickcur@yahoo.com 2005-02-07, 11:19 pm |
| I have a tif. I save it to jpg with certain quality, say (80%). Is the
compression ratio saved in the image file?
Thanks,
qq
| |
| All Things Mopar 2005-02-08, 4:15 am |
| > I have a tif. I save it to jpg with certain quality,
> say (80%). Is the compression ratio saved in the image
> file?
Hi.
I'm not sure what you mean by 80%. Perhaps you mean that
your file on your HD is 80% as large as the in-memory
version or perhaps you might mean that it is 20% as large
(i.e. it was reduced by 80%).
Assuming you're using PSP 7/8/9, JPEG compression off the
Save As Options button is a unitless scale from 1 to 100.
It is actually exponential, not linear, and not a
percentage reduction in file size.
1 will yield a file approximately half-size. I really
don't know what 100 does, but it'll certainly make
mincemeat out of your file!
I won't go any further into the tall weeds and confuse you
unless you have another question. But, to the question did
ask, NO, AFAIK, the JPEG compression factor is NOT stored
with the file.
If you really need to know what it is approximately, open
the file in question and run the JPEG Optimizer: Save As>
Options>Run Optimizer. Do a little experiemtation with the
1-100 factor, the Optimizer will show you a running count
of the file size. When you get close to the on-disk size,
you'll have the approximate JPEG compression factor.
If there's a direct way to do this, maybe more
knowledgeable about JPEG and PSP may answer your question.
--
ATM, aka Jerry
| |
| Gordon Richardson 2005-02-08, 4:15 am |
| A simple question, with a very complex answer. I spent some weeks writing
an article on this subject, so I won't try to give a summary:
http://www.photo.net/learn/jpeg/
<quickcur@yahoo.com> wrote in message
news:1107831555.775230.60510@l41g2000cwc.googlegroups.com...
> I have a tif. I save it to jpg with certain quality, say (80%). Is the
> compression ratio saved in the image file?
>
> Thanks,
>
> qq
| |
| Carl Frisk 2005-02-08, 4:15 am |
| I was just looking for the site a few days ago. Thanks for reposting.
--
....Carl Frisk
Anger is a brief madness.
- Horace, 20 B.C.
http://www.carlfrisk.com
"Gordon Richardson" <gordonrNO@SPAMiafrica.com> wrote in message news:2PqdnQFXIdTl2pXfRVn-uw@is.co.za...
>A simple question, with a very complex answer. I spent some weeks writing
> an article on this subject, so I won't try to give a summary:
> http://www.photo.net/learn/jpeg/
>
>
> <quickcur@yahoo.com> wrote in message
> news:1107831555.775230.60510@l41g2000cwc.googlegroups.com...
>
>
>
| |
|
| quickcur@yahoo.com wrote:
> I have a tif. I save it to jpg with certain quality, say (80%). Is the
> compression ratio saved in the image file?
Nope. There are no standard compression ratios.
:-)
Uni
>
> Thanks,
>
> qq
>
| |
| roshu 2005-02-10, 11:25 pm |
| Uni <no.email@no.email.invalid> wrote in message news:<4208541A.8000407@no.email.invalid>...[color=darkred]
> quickcur@yahoo.com wrote:
>
> Nope. There are no standard compression ratios.
>
> :-)
>
> Uni
>
It really depend on the sampling rate of the uncompressed image that u
start with. Generally JPEG gives 15-20% compression but if you start
with an oversmapled image, you can achieve higher numbers like 80% or
100%
| |
| Michael Daly 2005-02-11, 4:16 am |
| On 10-Feb-2005, linux4ritwik@yahoo.com (roshu) wrote:
> you can achieve higher numbers like [...] 100%
del *.*
Mike
| |
| Ben Pope 2005-02-11, 11:20 pm |
| Michael Daly wrote:
> On 10-Feb-2005, linux4ritwik@yahoo.com (roshu) wrote:
>
>
> del *.*
One of the more lossy compression systems, that one :-p
Ben
--
I'm not just a number. To many, I'm known as a String...
| |
|
| roshu wrote:
> Uni <no.email@no.email.invalid> wrote in message news:<4208541A.8000407@no.email.invalid>...
>
>
> It really depend on the sampling rate of the uncompressed image that u
> start with. Generally JPEG gives 15-20% compression but if you start
> with an oversmapled image, you can achieve higher numbers like 80% or
> 100%
Compression depends on content. A more busy image will compress less
than a less busy image. JPEG format was released too early. That is why
the JPEG committee never embedded the compression information into the
saved JPG.
Uni
| |
| Christian Gollwitzer 2005-02-12, 7:17 am |
| Uni wrote:
>
> Compression depends on content. A more busy image will compress less
> than a less busy image. JPEG format was released too early. That is why
> the JPEG committee never embedded the compression information into the
> saved JPG.
Hmm? A jpeg file (more accurately JFIF) contains the quantization tables used
for the compression, because they are needed to decompress the image. These
tables are the only exhausting source for the "compression quality" of the jpeg
image. The construction of the qtables from the "quality value" shown to the
user is arbitrary and depends on the compressor. You are right, that this
"quality setting" is normally not saved, but even if it would be, it could not
compared between applications.
Christian
| |
| A Soberon 2005-02-12, 6:20 pm |
| > Compression depends on content. A more busy image will compress less
> than a less busy image. JPEG format was released too early. That is why
> the JPEG committee never embedded the compression information into the
> saved JPG.
>
> Uni
don't you tire of sputtering stupidities?
| |
| Norbtach 2005-02-13, 11:18 pm |
| No, the compression ratio is NOT saved in the image file.
If you save a picture with a certain quality, you lose information
and you will never get that back
For a good explanation read this webpage.
http://www.photo.net/learn/jpeg/
Regards Robert
<quickcur@yahoo.com> wrote in message
news:1107831555.775230.60510@l41g2000cwc.googlegroups.com...
> I have a tif. I save it to jpg with certain quality, say (80%). Is the
> compression ratio saved in the image file?
>
> Thanks,
>
> qq
>
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