From jonathan_lees at unc.edu  Wed Apr 28 14:07:25 2004
From: jonathan_lees at unc.edu (jonathan_lees@unc.edu)
Date: Wed Apr 28 14:07:30 2004
Subject: [Rd] Re: postscript image problem (PR#6763)
Message-ID: <20040428120725.D150B10481@slim.kubism.ku.dk>

It is true that if you turn antialiasing
off on GV then the effect seems to disappear but that is just a cosmetic 
thing.
Other aspects of the figure are subsequently degraded, however.

I am really interested in converting the postscript to good JPEG images and
I can't get rid of the annoying lines when I use display or
convert (in LINUX).
If I could figure our how to get a good JPEG figure I would be
satisfied.

Thanks for any help.




paul murrell wrote:

>Hi
>
>
>  
>
>>Full_Name: Jonathan Lees
>>I am having trouble with the postscript output of images.
>>They have lines on them that are not supposed to be there.
>>I have noticed this on numerous trials of printing various images.
>>I looked at the postscript and I see that it
>>appears to plot each individual block - so perhaps occasionally the 
>>space between the blocks "leaks" through do to round off,
>>thus contaminating the image.
>>this could be solved if the image software used postscript
>>image plotting functions.
>>
>>Here is an example of some code:
>>
>>postscript(file ="test.ps" , onefile=FALSE, print.it=FALSE)
>>
>>
>>w<-5 #width of central square
>>m=w
>>xn<- 128; yn<- 128
>>im<- matrix(0,nrow=yn,ncol=xn)
>>xc<-floor(xn/2)+1;
>>yc<- floor(yn/2)+1 # centers of the image
>>im[(-m:m)+xc,(-m:m)+yc]<- 1
>>
>>image(im , col = cmap ); title('im=Original image')
>>
>>
>>dev.off()
>>
>>view this output with any postscript viewer (or printer)
>>and you will see extra lines on the plot.
>>    
>>
>
>
>Is this just caused by antialiasing on the postscript viewer.  I see this with
>anti-aliasing on, but it goes away if I turn antialiasing off.  Of course, that
>wouldn't explain the effect when a document is printed, but I don't get that.
>
>Paul
>  
>

-- 
===============================
Jonathan M. Lees
Associate Professor
University of North Carolina
Department of Geological Sciences
CB#3315, Mitchell Hall
Chapel Hill, NC 27599-3315

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[Rd] Re: postscript image problem (PR#6763)
jonathan_lees@unc.edu