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From Thomas DeWeese <Thomas.DeWe...@Kodak.com>
Subject Re: PNG gamma labeling
Date Thu, 11 Sep 2003 09:45:49 GMT
Peter Becker wrote:
> [was: Re: Text rendering changes after upgrade to 1.5]
> Jim Ley wrote:
>> "Peter Becker" <pbecker@dstc.edu.au> wrote in message
>> news:3F5FCB7B.7090102@dstc.edu.au...
>>> But let's not play the blame game -- I don't care whose fault it is, I
>>> just want the results to be good. At the moment I am not happy with the
>>> looks of my website in IE -- which I rarely see myself but unfortunately
>>> IE is still the most common browser, so I have to accomodate for that.
>>> It seems to be somehow the combination of Batik's rendering of the SVG
>>> into PNG with IE's rendering of the PNG onto the screen that causes the
>>> problem -- most programs I tried display the PNG as I want it.
>> You might want to read Henri Sivonen's review:
>> http://www.hut.fi/u/hsivonen/png-gamma.html
> Good reference, thanks for this -- it explains quite a lot. But my 
> conclusion from this article and this page linked from it:
>  http://www.hut.fi/u/hsivonen/png-gamma-test-results.html
> is that I want to encode PNGs without gamma information. That would 
> break some Opera versions and some (all?) Safari versions, but (a) these 
> are way less important for me than IE and (b) it seems to be that it is 
> their implementation which is on the wrong side of things. Also it seems 
> that unless Batik does some big magic it can't really know for sure 
> which gamma value to use -- so attaching it to the PNGs is also on the 
> wrong side of things. Did I get that right?
> Is there some option to get Batik not to encode gamma in PNGs? I 
> remember having hacked these bits of the code a while ago, but I think I 
> just tweaked the numbers. How do I get unlabeled PNGs from Batik?

    I sent my previous response because it contained lots of useful information.
Currently Batik (in fact our PNG transcoder) will _always_ generate a gAMA
chunk.  The code for this is the '.5' rounding fix I mentioned in my previous
note.  You would need to add a new parameter to the PNGEncodeParam object
and then a new transcoder hint to the PNGTranscoder and then add it to the
command line handing in the rasterizer - to fully export it.

    As I said in my other note Batik would probably accept a proper contribution
but generating broken PNG's is not something I will spend any time on.

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