Take a look at the transformations tutorial.

http://matplotlib.sourceforge.net/users/transforms_tutorial.html

To convert from data -> pixel coordinates, use the axes transData transformation

In [1]: ax = gca()

In [2]: ax.transData.transform((0.5, 0.5))

Out[2]: array([ 333.125, 245. ])

You can also use mpl events to inspect the coordinates of the point

under the mouse

In [3]: fig = gcf()

In [4]: def on_click(event):

...: print event.x, event.y

...:

...:

In [5]: cid = fig.canvas.mpl_connect('button_press_event', on_click)

In [6]: 188 166.0

300 227.0

384 292.0

In [7]: fig.canvas.mpl_disconnect(cid)

See http://matplotlib.sourceforge.net/users/event_handling.html for more info.

JDH

## ···

On Wed, Sep 29, 2010 at 4:44 AM, Alexander Dietz <alexanderdietz1@...982...> wrote:

I would like to know how to find out the extend of the actual image in a

plot, in units of pixels.

As example I have attached a plot which is essentially empty. The lower left

corner is indicated by a red dot - what pixel position does this location

have? When opening this image in e.g. kview it is easy to find out that this

left corner of the actual plot corresponds to pixel (100,540). And so the

upper right corner (the yellow dot) is (720,60).

But how do I find out these coordinates when generating such a plot with

matplotlib? Are there some variables of the axis or the actual plot that

contain these numbers?