Re: [Matplotlib-users] Why pixel marker size is 4 pixels?

[Chris <pl...@gm...>]

Thanks JJ.

The problem seems not to be a size issue --  markersize has no effect
when use marker="," (pixel).  I have also tried to turn off aa, and it
doesn't help either.  I also tried different backends.  The PNG output
from Agg and Cairo is slightly different: Agg's point has 4 solid
pixel, while Cairo's has 4 pixel with random shade.

Postscript output has the same problem.  The "pixel" in an EPS file
generated by mpl is significantly bigger than that from another
drawing program I used.

The problem occurs in all my plotting scripts, e.g., this basic one:

[CODE]
import numpy as np

x=np.arange(100)
y=np.random.randn(100)

ioff()
fig=gcf()
fig.clf()

ax=fig.add_axes(0.15,0.1,0.8, 0.85)
ax.plot(x,y,"k,")

ion()
fig.canvas.draw()
[/CODE]

Here is how I identify the problem:
1. use the above script to plot on screen
2. savefig("plot.png")
3. open plot.png in GIMP and check the pixel size.

I also attached the two PNG files generated with Agg and Cairo backends.


On Sun, Feb 5, 2012 at 6:45 AM, Jae-Joon Lee <lee...@gm...> wrote:
> How are you plotting your points.
>
> If you use *plot*, there is a *markersize* parameter.
> If you use *scatter*, the third argument controls the marker size.
>
> But you may actually complaining about other issues, e.g.,
> antialiasing, etc. So, if above are not your answer, please post a
> complete example and describe your problem in more detail.
>
> Regards,
>
> -JJ
>
>
> On Sat, Feb 4, 2012 at 2:15 PM, Chris <pl...@gm...> wrote:
>> I noticed this a few years back, but left it aside because most of the
>> time I can live with it.  Recently I need to make a few plots
>> containing a few million points, and 4 pixels for a point is a
>> disaster.  So my question is why the pixel marker size is set at 4
>> pixels?  And is there anyway to change it to a single pixel?
>>
>> Thanks,
>> Chris
>>
>> ------------------------------------------------------------------------------
>> Try before you buy = See our experts in action!
>> The most comprehensive online learning library for Microsoft developers
>> is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3,
>> Metro Style Apps, more. Free future releases when you subscribe now!
>> http://p.sf.net/sfu/learndevnow-dev2
>> _______________________________________________
>> Matplotlib-users mailing list
>> Mat...@li...
>> https://lists.sourceforge.net/lists/listinfo/matplotlib-users