Hello all,

I have noticed some quality issues with gradients (shades) produced with pgf.  The problem only happens with I compile with pdflatex but I do not see the problem when I do latex->dvips->ps2pdf.  I am running on a stock ubuntu hardy machine which installs pgf version 1.18 (I do not know if this is still a problem with version 2.0).

You can reproduce my problem with the following steps or (or download the output of my steps from the links I include):

1) Download the following example from the PGF and TikZ examples gallery (I have this issue with any tikzpicture with a shade - just using a standard example):

http://www.fauskes.net/pgftikzexamples/parabola-plot/

2) Compile with latex->dvips->ps2pdf  (I did the following)

latex parabola-plot.tex; dvips -o parabola-plot_dvips.ps parabola-plot.dvi; ps2pdf parabola-plot_dvips.ps

You can download the output here:

http://butala.csl.uiuc.edu/~butala/parabola-plot_dvips.pdf

3) Compile with pdflatex  (I did the following)

pdflatex parabola-plot.tex

You can download the output here:

http://butala.csl.uiuc.edu/~butala/parabola-plot.pdf


Note that the gradient in the output generated with pdflatex (parabola-plot.pdf) seems to be composed of many horizontal lines whereas the gradient in the latex->dvips->ps2pdf version (parabola-plot_dvips.pdf) is perfectly smooth.

OK, now this may just be an artifact of my pdf viewer (I use evince).&nbsp ; However, the real reason that I am asking about this is that I use the following to produce a nice background for large (4 feet by 3 feet) posters:

\newenvironment{poster}
{%
\small\noindent\ignorespaces\pagestyle{empty}
\begin{tikzpicture}[remember picture,overlay]
\shade [top color=bgGradOne,bottom color=bgGradTwo]
(current page.north west) rectangle +(\paperwidth,-0.1\paperheight);
\shade [top color=bgGradTwo,bottom color=bgGradOne]
(current page.south east) rectangle +(-\paperwidth,0.9\paperheight);
\end{tikzpicture}
\vfill\begin{center}\begin{minipage}[c][\posterheight]{\posterwidth}
}
{\end{minipage}\end{center}\vfill\ignorespacesafterend}


When I printed a poster at kinkos using the above to produce the gradient background, I noticed the unsmooth horizontal lines - just like in the example I showed above with pdflatex.  I did not try to print a latex->dvips-&gt ;ps2pdf version of the poster - poor grad. students usually cannot afford to burn $100 for testing purposes :).

Any ideas?  Thanks in advance for any ideas!

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- Mark