Re: [Plplot-devel] Ghost grid over shading with cairo devices

[Andrew R. <and...@us...>]

On Tue, Feb 22, 2011 at 09:19:45AM +0100, J C Gonzalez wrote:
> Hi.
> 
> I'm trying to use PLPlot to generate some world maps.  I *must*
> generate a JPEG file, but the jpeg device for the PLPlot version
> installed in my system produces ugly results.  I thought of using
> device pngcairo (since png device looks also not good enough),
> and then convert the resulting png file to jpeg.  The problem I'm
> facing is that I get a sort of fine grid in the image that I
> plot.
> 
> It would be easier to understand if I say that I get the same
> effect using device pngcairo with example 16 (shading).  The
> shade plot generated in this example shows a grid plotted over
> the shading surface, that is not shown in jpeg/png/win/ps
> devices.  It seems to be an artifact related to the cairo family
> of devices.
> 
> Does anybody know how to remove this grid?

Is it a greyish looking grid? I have seen a similar effect when using
some of the Linux tools to convert between different image formats. I
believe it is due to transparency issues. I have never seen it with 
the plplot cairo devices so, as Alan says, my first guess would be a
problem with your version of cairo. You could also try a different 
image viewer to see if that makes a difference. What viewer are you
using?

Andrew