Chris B schrieb:
> 
> Well, yes and no. JPEG is a lossy format (it's designed that way), but I 
> find it by far and away the most convenient when working on graphics 
> destined for web pages. Any implication that it's not a worthy format to 
> be supported by POV-Ray makes me a tad nervous. I think it should find 
> its way into the documentation, with a warning that it's not a loss-free 
> format and that the results will unavoidably contain JPEG artifacts. 
> People could then simply use another format for any process that 
> requires some sort of top quality master.

I think the rationale behind deliberately hiding this feature is that 
for it to come anywhere close to being /useful/, some more work would 
need to be invested; the default quality would have to be increased, and 
ideally a quality parameter would have to be added.

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> "Chris B" <nom### [at] nomailcom> wrote:
>> "Charles C" <nomail@nomail> wrote in message
>> news:web.4ac9720b3f8a411cac4259f0@news.povray.org...
>>> I'd never heard of "+fj"!   It's always seemed missing even if jpeg is a
>>> better
>>> distribution format than a "mastering" format.  I can imagine there being
>>> some
>>> rare uses.  That said, I have to agree with Trevor's comment. :)
>>>
>> Well, yes and no. JPEG is a lossy format (it's designed that way), but I
>> find it by far and away the most convenient when working on graphics
>> destined for web pages. Any implication that it's not a worthy format to be
>> supported by POV-Ray makes me a tad nervous. I think it should find its way
>> into the documentation, with a warning that it's not a loss-free format and
>> that the results will unavoidably contain JPEG artifacts. People could then
>> simply use another format for any process that requires some sort of top
>> quality master.
>>
>> Regards,
>> Chris B.
> 
> Sorry, no anxiety intended. ;)  I agree JPEG output is a good option to have
> available.  One feature which could make it even better would be a quality
> option. For example "+fjxx" where "xx" is a numeric quality level similar to
> what you can enter when saving a JPEG in GIMP.
> 
> (Disclaimer: I don't know just how quick or easy this would be to implement, and
> I imagine it would be of relatively low priority compared to other things.)
> 
> I think depending on the content of an image, JPEG can be more distracting than
> at other times.  For instance, I tried +fj on a test render with very simple
> textures, some fine detail and a blue sky sphere.  It looked bad.   I suspect
> the more a rendering looks like a photo (i.e. no shortage of detail so you're
> not staring at one little spot which you can't see clearly), the less
> distracting JPEG artifacts might be for a given compression level.
> 
> Charles
> 
> 
> 
Also, using AA can greatly help.

Alain

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"clipka" <ano### [at] anonymousorg> wrote in message 
news:4aca85a1$1@news.povray.org...
> Chris B schrieb:
>>
>> Well, yes and no. JPEG is a lossy format (it's designed that way), but I 
>> find it by far and away the most convenient when working on graphics 
>> destined for web pages. Any implication that it's not a worthy format to 
>> be supported by POV-Ray makes me a tad nervous. I think it should find 
>> its way into the documentation, with a warning that it's not a loss-free 
>> format and that the results will unavoidably contain JPEG artifacts. 
>> People could then simply use another format for any process that requires 
>> some sort of top quality master.
>
> I think the rationale behind deliberately hiding this feature is that for 
> it to come anywhere close to being /useful/, some more work would need to 
> be invested; the default quality would have to be increased, and ideally a 
> quality parameter would have to be added.

Ahh! Well I first learned about it on these newsgroups years ago, so I don't 
think I've let a secret slip that wasn't already out there.

I don't know the POV source, d'you think that would be a big 
investment/change?  Is the JPEG compression just a standard codec library 
call at the end of the render?

Regards,
Chris B.

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Chris B schrieb:

> I don't know the POV source, d'you think that would be a big 
> investment/change?  Is the JPEG compression just a standard codec 
> library call at the end of the render?

I... um.... well, I guess it is.

(*browses though the code*)

Ehm... yup - the change would be minimal indeed... unless you were 
hoping for an effort lower than zero :-)

Fun facts to know: There already /is/ a JPEG compression quality 
parameter in POV-Ray, at least with 3.7.0.beta.34. Setting the .ini file 
parameter "Compression" to any integer value from 2 to 100 should do the 
job. Theoretically. Didn't test, just looked at the code.


The parameter is apparently intended to be format-specific; for JPEG, 
values 0 (default) and 1 are short-circuited to produce a fairly 
high-quality image, while any other value in the range of 2 to 100 is 
passsed to the JPEG library as the encoding quality parameter (2 = poor, 
100 = maximum quality). Values lower than 0 or higher than 100 are 
clipped to the 0..100 range.

Other file formats currently don't use the Compression parameter.

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"clipka" <ano### [at] anonymousorg> wrote in message 
news:4ace245f@news.povray.org...
> Chris B schrieb:
>
>> I don't know the POV source, d'you think that would be a big 
>> investment/change?  Is the JPEG compression just a standard codec library 
>> call at the end of the render?
>
> I... um.... well, I guess it is.
>
> (*browses though the code*)
>
> Ehm... yup - the change would be minimal indeed... unless you were hoping 
> for an effort lower than zero :-)

Nope! Zero effort is low enough for me :-)


> Fun facts to know: There already /is/ a JPEG compression quality parameter 
> in POV-Ray, at least with 3.7.0.beta.34. Setting the .ini file parameter 
> "Compression" to any integer value from 2 to 100 should do the job. 
> Theoretically. Didn't test, just looked at the code.

Indeed I don't mind a smidgen above zero, so I'll be ok with trying that out 
and adding something into the Wiki.
Is there a corresponding command-line option?

Regards,
Chris B.

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Chris B schrieb:

> Is there a corresponding command-line option?

Apparently not, only the .INI file option.

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clipka <ano### [at] anonymousorg> wrote:
> Chris B schrieb:
>
> > Is there a corresponding command-line option?
>
> Apparently not, only the .INI file option.

I bet +fjxx could really be handy for somebody wanting to post a test render in
p.b.i.
Charles

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"Chris B" <nom### [at] nomailcom> wrote in message 
news:4ace286b@news.povray.org...
> Indeed I don't mind a smidgen above zero, so I'll be ok with trying that 
> out and adding something into the Wiki.
> Is there a corresponding command-line option?

you additions have been merged into the main doc ....

Jim

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"Jim Holsenback" <jho### [at] povrayorg> wrote in message 
news:4acf77ce$1@news.povray.org...
> "Chris B" <nom### [at] nomailcom> wrote in message 
> news:4ace286b@news.povray.org...
>> Indeed I don't mind a smidgen above zero, so I'll be ok with trying that 
>> out and adding something into the Wiki.
>> Is there a corresponding command-line option?
>
> you additions have been merged into the main doc ....
>

Thanks Jim.

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