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Re: Noise in vector graphics generated by pcolor


From: Ben Abbott
Subject: Re: Noise in vector graphics generated by pcolor
Date: Thu, 27 Feb 2014 09:18:18 -0500

On Feb 27, 2014, at 4:33 AM, gdudziuk <address@hidden> wrote:

> This post will be pretty long.
> My problem is the following. I generate an .EPS graphic using Octave and it
> looks fine. Next, I embed it in a LaTeX file, create a PDF. Then, it turns
> out that my graphic has some noise, when viewed under Linux within the PDF
> file.
> Why I write about it here? Because it seems that it is Octave fault (or more
> precisely - of pcolor function). I will explain it in more detail in a
> moment.
> First, let me say more on what I am doing and observing. I use *pcolor*
> function to plot data contained in a matrix --- I call *pcolor(xx,yy,data)*,
> where *xx* and *yy* contain the mesh coordinates and *data* contain the data
> to be plotted. Next, I use various options to adjust the resulting figure:
> *shading*, *colormap*, *caxis*, *axis*, *xlabel*, *ylabel*, title. The
> argument for *shading* is *interp*. Ultimately, I save the result to file
> using *print* function: *print -deps "-S400,400" -color file.eps*The
> generated file looks nice. Below, a screenshot of the result is presented:
> <http://octave.1599824.n4.nabble.com/file/n4662410/pcolor_img1.png> 
> Next, I use my graphic in a LaTeX document and, basing on this document,
> generate a PDF. Then, I observe that my graphic, which look so nice in .eps
> file, looks very noisy when embedded in the subject PDF. Below, I present a
> screenshot of what I see in the PDF file, generated from LaTeX code:
> <http://octave.1599824.n4.nabble.com/file/n4662410/pcolor_img2.png> 

The effect your are seeing appears to be from triangular meshing and 
interpolation.

Can you tell us which graphics toolkit you were using? (i.e. either gnuplot or 
fltk).  I'd guess you are using fltk.

Have you tried switching the graphics_toolkit?  You can try gnuplot by ....

        close all
        graphics_toolkit gnuplot

... and then recreate your plot.

And did you print the PDF file? Does it also contain the undesired features?

Ben

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