Option to set the quality of JPG in percent - Feature Requests - CHDK Forum
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Option to set the quality of JPG in percent

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Offline thunderstorm

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Option to set the quality of JPG in percent
« on: 10 / April / 2008, 15:33:14 »
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The "superfine", "fine", "normal", are for the normal users and they don't tell so much...

It would be usefull to be able to set 100% quality or 1%... if needed.
What about encoding JPEG 2000 which has higher bit depth? Is it possible to do it?

What is the camera quality [%] at "superfine" mode?
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Offline gango

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Re: Option to set the quality of JPG in percent
« Reply #1 on: 10 / April / 2008, 16:05:16 »
Quote from: thunderstorm on 10 / April / 2008, 15:33:14
What is the camera quality [%] at "superfine" mode?

"superfine" is about 98% jpeg quality.
"fine" is about 94%.
"normal" is simply horrible.
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Offline GrAnd

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Re: Option to set the quality of JPG in percent
« Reply #2 on: 10 / April / 2008, 16:49:23 »
Quote from: gango on 10 / April / 2008, 16:05:16
"superfine" is about 98% jpeg quality.
"fine" is about 94%.

I suspect there should be more than 4% difference between these two modes...
"superfine" is more likely 85-90%
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Offline thunderstorm

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Re: Option to set the quality of JPG in percent
« Reply #3 on: 10 / April / 2008, 17:18:15 »
Than there -must- be a hack to be able to save 100% quality JPG! :)

It will allow us to shoot the best JPG's strait into the camara memory, with no need for converting between RAW --> JPG for pictures/scenes that do not require RAW shooting.

98% is not enough!
The file size is heavily compressed between 100%-90% quality settings.
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Offline GrAnd

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Re: Option to set the quality of JPG in percent
« Reply #4 on: 10 / April / 2008, 17:29:09 »
Quote from: thunderstorm on 10 / April / 2008, 17:18:15
The file size is heavily compressed between 100%-90% quality settings.

I took a JPG file from A610. It was 2MB. Then I opened it in Photoshop and tried to export it with several quality settings. I've got the similar size on 85%. And I've got 3MB file if I set the quality to 100%.
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Offline Barney Fife

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Re: Option to set the quality of JPG in percent
« Reply #5 on: 10 / April / 2008, 18:27:50 »
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« Last Edit: 22 / April / 2008, 17:17:37 by Barney Fife »
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Offline ripwink

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Re: Option to set the quality of JPG in percent
« Reply #6 on: 10 / April / 2008, 23:04:48 »
JPEGsnoop gives a lot of information on the quality of JPEGS. You may like to check this utility.
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Offline gabriele

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Re: Option to set the quality of JPG in percent
« Reply #7 on: 14 / April / 2008, 06:54:23 »
Sorry for the lenght of the post, but this is the output I got with JPEGsnoop from a picture taken with my A630 with superfine quality:

  Precision=8 bits
  Destination ID=0 (Luminance)
    DQT, Row #0:   1   1   1   1   1   2   3   3
    DQT, Row #1:   1   1   1   1   1   3   3   3
    DQT, Row #2:   1   1   1   1   2   3   3   3
    DQT, Row #3:   1   1   1   1   2   4   4   3
    DQT, Row #4:   1   1   3   4   4   6   6   4
    DQT, Row #5:   1   2   3   3   4   5   6   5
    DQT, Row #6:   2   3   4   4   5   6   6   5
    DQT, Row #7:   5   5   5   5   5   5   5   5
    Approx quality factor = 97.24 (scaling=5.52 variance=1.65)
  ----
  Precision=8 bits
  Destination ID=1 (Chrominance)
    DQT, Row #0:   1   1   2   4   6  11  11  11
    DQT, Row #1:   1   1   2   4   8  11  11  11
    DQT, Row #2:   2   2   3   4  11  11  11  11
    DQT, Row #3:   4   4   4   5  11  11  11  11
    DQT, Row #4:   6   8  11  11  11  11  11  11
    DQT, Row #5:  11  11  11  11  11  11  11  11
    DQT, Row #6:  11  11  11  11  11  11  11  11
    DQT, Row #7:  11  11  11  11  11  11  11  11
    Approx quality factor = 95.17 (scaling=9.67 variance=5.29)
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Offline yg2007

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Re: Option to set the quality of JPG in percent
« Reply #8 on: 14 / April / 2008, 10:50:49 »
Quote from: Barney Fife on 10 / April / 2008, 18:27:50
There's some little utility out there somewhere in net-land, that allows you to run it on any JPG file and it's supposed to tell you the compression sub-sampling used as well as an estimated percentage of the compression. I don't recall the name of the program or where to find it. But if any of you find that you could use it to get more exacting results of what's really being used.





jpgQ -JPEG Quality Estimator is a kind of such utility. you might want to check this out: jpgQ Estimator
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Offline jetzt

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Re: Option to set the quality of JPG in percent
« Reply #9 on: 14 / April / 2008, 11:10:03 »
Quote
jpgQ -JPEG Quality Estimator is a kind of such utility. you might want to check this out: jpgQ Estimator
Why not you, if I'm allowed to ask? :P
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