Re: [Gnuplot-info] ugly data-point rounding error

[some_guy <som...@ya...>]

You are right. As I'm using gnuplot 4.2 patchlevel 4, the effect is indeed
smaller. SVG_SCALE=10 and all data-points are rounded to a tenth of a pixel.

This is much more satisfying, but errors are still visible. Could we set
SVG_SCALE to 100 or 1000 ?



Thomas Sefzick wrote:
> 
> don't know with which version of gnuplot these plots were
> generated, but since version 4.0 SVG_SCALE is 10.
> i'm not able to reproduce this poor quality with
> gnuplot 4.0, 4.2.5 and 4.3-cvs.
> 
> 
> Ryan Davis-4 wrote:
>> 
>> Hi,
>> 
>> I realized some strange jiggling of plotlines in many
>> svg-gnuplot-graphics. Especially when a plot is supposed to be precise
>> and many datapoints are used, the problem gets worse.
>> 
>> Seeking for the bug in the sourcecode, it turned out the problem is that
>> every
>> datapoint to be drawn is handed over as an integer, e.g.
>> 
>> TERM_PUBLIC void SVG_vector (unsigned int x, unsigned int y) .
>> 
>> In case of the standard-settings SVG_SCALE=1 , this means, that every
>> point is binned to integer-pixelvalues, rendering the whole sense of
>> vector-graphics useless.
>> 
>> Some examples where the problem is directly visible:
>> http://commons.wikimedia.org/wiki/File:Normal_distribution_cdf.svg
>> http://commons.wikimedia.org/wiki/File:Soliton_2nd_order.svg (see the
>> grid on the ground which is supposed to be
>>  flat)
>> http://commons.wikimedia.org/wiki/File:Arcsin_plot.svg
>> 
>> if you don't see what I mean, take a look at the 2000px versions. Many
>> graphics of this kind can be found on the internet.
>> 
>> 
>> Since it's not a problem concerning only svg-export but a flaw rooting
>> deep
>> inside gnuplot, i cant't correct it by myself. Gnuplot is used in many
>> scientific applications and I'm absolutely convinced, that treating
>> data-points as float values is the only reasonable choice. Those
>> terminals who only support raster-images can round the values later on,
>> and even they can take advantage of precisely located data-samples. As
>> a user, I don't know how to solve it, so I hope you can fix this in the
>> sourcecode. Floating-point output to svg-files with at least 3 digits
>> precision seems essential.
>> 
>> thanks in advance!
>> 
>> 
>> 
>> btw: did you notice inkscape's inability to interpret the
>> "color"-attributes in gnuplot-created svg-graphics? maybe it helps to
>>  assign stroke- and fill-colors directly.
>> 
>> 
>> 
>> Gnuplot-info mailing list
>> Gnu...@li...
>> https://lists.sourceforge.net/lists/listinfo/gnuplot-info
>> 
>> 
> 
> 

-- 
View this message in context: http://www.nabble.com/ugly-data-point-rounding-error-tp24942864p24983370.html
Sent from the Gnuplot - User mailing list archive at Nabble.com.