matplotlib-devel Mailing List for matplotlib

Hello all,
Earlier today I looked into a problem someone on the users list was
having with imread working on a binary png file of his (attached). The
array returned does not correspond to the picture, as verified by
imshow'ing the imread'd file, which results in a distorted image with
rainbow colouring at parts. After working through how imread would
handle his file, it seems the problem has to be somewhere in
matplotlib._png.read_png, which stems from matplotlib/src/_png.cpp in
the source tree. Interestingly enough, using the function pil_to_array
from matplotlib.image on the output of Image.open(fname) works
correctly on the file. I plan on poking around in the cpp file more
myself later tonight, but I was wondering if anyone more familiar with
matplotlib's png-handling could see something immediately obvious that
would break imread's capabilities on binary PNGs.
Josh

On Wed, Oct 22, 2008 at 12:03 PM, Adeodato Simó <da...@ne...> wrote:
> In http://matplotlib.sourceforge.net/users/pyplot_tutorial.html it says:
>
> | You may be wondering why the x-axis ranges from 0-3 and the y-axis
> | from 1-4.
>
> The axis in the image ranges from 0 to 2 (X) and from 1 to 3 (Y).
Thanks, fixed in svn 6309 (but not yet pushed out to the site)

Hi,
 Eric, I will be happy to test your possible fix too. I have similar
problem with autoscaling shared axes like you Mark.
David
Mark Bakker a écrit :
> Thanks Eric.
> 
> You know that this has been on my wish list for a long time.
> 
> Let me know if I can test anything or help in any other way,
> 
> Mark
> 
> On Wed, Oct 22, 2008 at 10:54 AM, Eric Firing <ef...@ha...
> <mailto:ef...@ha...>> wrote:
> 
> Mark Bakker wrote:
> 
> Hello list (especially Erik, who can fix this I hope) -
> 
> I have had problems with shared axes, especially when one of the
> axis has an aspect ratio that is set 'equal'. It has been
> discussed on the list before (mostly with Erik Firing), but it
> hasn't been fixed yet. What I want to do is have two plots. The
> top plot has an aspect ratio that is 'equal'. The idea is to
> have a contour plot in the top figure, while the bottom figure
> gives a cross-sectional picture of what I am plotting. This used
> to work well (quite some time ago), including zooming and such.
> But now I cannot plot it at all, let alone zoom.
> 
> My first problem is when I add a subplot with a shared x-axis,
> it changes the limits on the original x-axis. That seems to be a
> bug:
> ax1 = subplot(211)
> plot([1,2,3]) # Now the limits of the x-axis go from 0 to 2.
> subplot(212,sharex=ax1) # Now the limits of both x-axis go from
> 0 to 1.
> 
> After all, the new subplot shares the axis with the existing
> subplot, so why doesn't it copy the axis limits from that subplot?
> 
> 
> I may have the fix for this, but I need more time to check and
> refine it--and try to make sure that I don't break anything else in
> the process.
> 
> 
> 
> But the bigger problem occurs when I want the aspect ratio of
> one of the first axis to be 'equal'.
> 
> ax1 = subplot(211,aspect='equal')
> plot([1,2,3]) subplot(212,sharex=ax1)
> 
> The second subplot is added, but the length of the graph is not
> the same as for the first subplot. It also resets the xlimits to
> go from 0 to 1, as before, which means the first subplot becomes
> unreadable (it still enforces 'equal' in the first subplot by
> changing the limits of the y-axis). When I now change the limits
> on the x-axis, the aspect ratio is not equal anymore
> 
> 
> I will see what I can do. There are definitely some bugs that need
> to be squashed.
> 
> Eric
> 
> 
> ax1.set_xlim(0,2)
> draw()
> 
> Thanks for your help. I am willing to help in testing any changes.
> 
> Best regards, Mark
> 
> 
> 
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