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Groups > comp.graphics.apps.gnuplot > #3302

Re: Ticket 1782: plot with image broken in CVS

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Stephan Böttcher wrote:

> Ethan A Merritt <EAMerritt@gmail.com> writes:
> 
>> Patch and possible work-around attached to the original Bug Report.
>> https://sourceforge.net/p/gnuplot/bugs/1782/
> 
> Thanks.
> 
> Well, when I specify which column shall go to the x-coordinate and which
> column contains y-coodinates, there shall be no room for
> misunderstanding that.  "using x:y:cb" is umambiguous, isn't it?

Image data is not normally provide point-by-point.
A *.png file or a *.bmp file or whatever is a stream of 
intensity/color values with some meta-information that indicates
how to split that stream into rows and columns.  

Obviously you can specify the content of an image by describing
each pixel in terms of its individual coordinates, but that is
not the normal case.


> The only workaround I see is sticking with 5.0.3 until this is fixed.

That may be a solution for your particular input data stream, but
5.0.3 is known to incorrectly handle similar streams.
See in particular Bug #1767.

> I understand that the image plots may have a hard time to figure out
> the binning of the data.  That is why my scripts produce very
> unambiguous data files:
> 
> x1 y1 z11
> x2 y1 z12
> x3 y1 z13
> x4 y1 0
> 
> x1 y2 z21
> x2 y2 z22
> x3 y2 z23
> x4 y2 0
> 
> x1 y3 z31
> x2 y3 z32
> x3 y3 z33
> x4 y3 0
> 
> x1 y4 0
> x2 y4 0
> x3 y4 0
> x4 y4 0
> 
> These worked fine since the early days of "pm3d corners2color c1".

Plot styles "with pm3d" and "with image" are very different things!
It might be that your plot would come out correctly if treated as
pm3d data. You could try it.
You could also try plotting "with points pointtype 5 linecolor variable"

> If the new image parser misunderstands these files it is very broken.

What is obvious to you may not be so obvious to a stupid program.
The file layout you describe above does not match any image convention
that gnuplot knows about.  It can read each line as a an [x,y,z] point, 
or read each blank-line-separated block as a line segment.
In pm3d mode it can fit individual points onto a gridded surface,
but that is not part of normal image processing.

> I do not see how a transpose option is needed with this kind of
> datafile.  As long as it is needed something is broken.  Matrix type
> data may be a different issue, I never used that, yet.

In the case of the earlier bugs, transposing the internal values of
x and y restored the "correct" image.  That may not be the case for
your data but I thought it was worth a try as a quick work-around.

> And why did the PDF output filesize blow up out of proportion with 5.1
> compared to 5.0.3?

So far as I know, it has not.  If you can provide a script (with data if
needed) that shows a drastically different file size for the same plot
I will look into it.  The pair of files you attached to your bug report
clearly do not contain the same plot, so it's not fair to compare file
sizes.
	
	Ethan

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Thread

Ticket 1782: plot with image broken in CVS boettcher@physik.uni-kiel.de (Stephan I Böttcher) - 2016-04-19 23:19 +0200
  Re: Ticket 1782: plot with image broken in CVS Ethan A Merritt <EAMerritt@gmail.com> - 2016-04-19 21:07 -0700
    Re: Ticket 1782: plot with image broken in CVS boettcher@physik.uni-kiel.de (Stephan Böttcher) - 2016-04-20 17:06 +0200
      Re: Ticket 1782: plot with image broken in CVS Ethan A Merritt <sfeam@users.sourceforge.net> - 2016-04-20 12:13 -0700
        Re: Ticket 1782: plot with image broken in CVS boettcher@physik.uni-kiel.de (Stephan Böttcher) - 2016-04-20 22:36 +0200
          Re: Ticket 1782: plot with image broken in CVS Ethan A Merritt <EAMerritt@gmail.com> - 2016-04-20 21:15 -0700
            Re: Ticket 1782: plot with image broken in CVS boettcher@physik.uni-kiel.de (Stephan Böttcher) - 2016-04-21 12:42 +0200

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