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Re: Sometimes noise and resources about colours

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Op maandag 26 nov 2012 10:50 CET schreef Chris:

>>> That looks to me like the effects of halftoning, because the output
>>> doesn't have enough colours to accurately portray the colours you've
>>> used in the Postscript.
>>
>> But I am only using two colours.
>
> This really isn't the place to give a treatise on colour representation
> but..... in a very simplified form......

You went a lot deeper as I mend. ;-) I just mend which colour
combinations to use. Until now I like yellow on darkblue. Yellow on
red is not to bad also, but should not be used to much I think. My
other experiments do not make me happy until now. :-(


>>> You can do something like:
>>> gs -sDEVICE=png16m -r300 -o <output>.png <input>.ps
>>
>> The first try does not look promising. With the -r300 I get a to big
>> picture. When I leave it out the size is correct.
>
> Well, I did say you should read up on the Ghostscript options - 
> *especially* "-r". The size is "correct" in both cases.

Not when I put an picture on FaceBook and it is not allowed to be
wider as 404 pixels.


>> But I still have the
>> noise. Also the kerning is wrong. The letters are to close together now.
>
> The kerning is not wrong. You've asked for 72 dpi (that's Ghostscript's
> default resolution), that severely limits the accuracy with which we can 
> place glyphs, and features within glyphs, and what you're seeing is the 
> result of that.

Then I properly best can make a PDF first and convert that to an png.

I had the same with eps files. You can immediately convert them with
convert, but get a very bad result.


> As with colours, Postscript provides a continuous plane in "user space"
> which the interpreter must convert to a discrete coordinate space for the 
> image file output, using a specific set of rules (scan conversion). The 
> lower the resolution, the greater error you can expect during that 
> conversion.
>
>> The command I am using is:
>> gs -sDEVICE=png16m -o keepYourHead2.png keepYourHead.ps
>>
>> The 2 is to keep the file from the other generate to compare them.
>>
>> The generated files are posted at:
>> http://decebal.nl/postscript/keepYourHead.png
>> http://decebal.nl/postscript/keepYourHead2.png
>
> I don't see any "noise" in those. I do see that that the first one looks
> like it is anti-aliased (hence the slight fuzziness around the glyphs), 
> whilst the second is not. If you want anti-aliased output direct from 
> Ghostscript, lookup the TextAlphaBits and GraphicsAlphaBits command line 
> options.

I mean the anti-aliasing. And I really see it in both. I do not want
anti-aliasing. I'll look into the commands you gave. The option
+antialias with convert does not work very well. When converting from
the pdf there is already some fuzziness. So I should find a way to
prevent it cropping up in the pdf.


>> By the way, I even see noise in the pdf, but less and only under the
>> text:
>> http://decebal.nl/postscript/keepYourHead.pdf
>
> Again, I don't see any noise in that, using evince/poppler, xpdf, 
> Ghostscript and Acrobat.

If you look under the letters, there is a little shadow.

I do not see fuzziness at:
    https://www.facebook.com/photo.php?fbid=445065655531047

The only problem is: I do not have the used script anymore. :-(

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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Thread

Sometimes noise and resources about colours Cecil Westerhof <Cecil@decebal.nl> - 2012-11-25 22:43 +0100
  Re: Sometimes noise and resources about colours Chris <cjl@spamcop.net> - 2012-11-25 22:03 +0000
    Re: Sometimes noise and resources about colours Cecil Westerhof <Cecil@decebal.nl> - 2012-11-25 23:54 +0100
      Re: Sometimes noise and resources about colours Chris <cjl@spamcop.net> - 2012-11-26 09:50 +0000
        Re: Sometimes noise and resources about colours Cecil Westerhof <Cecil@decebal.nl> - 2012-11-26 21:43 +0100
          Re: Sometimes noise and resources about colours Chris <cjl@spamcop.net> - 2012-11-26 21:00 +0000
            Re: Sometimes noise and resources about colours Cecil Westerhof <Cecil@decebal.nl> - 2012-11-26 23:19 +0100
              Re: Sometimes noise and resources about colours Chris <cjl@spamcop.net> - 2012-11-26 22:36 +0000
                Re: Sometimes noise and resources about colours Cecil Westerhof <Cecil@decebal.nl> - 2012-11-27 00:41 +0100
          Re: Sometimes noise and resources about colours Cecil Westerhof <Cecil@decebal.nl> - 2012-11-26 22:15 +0100

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