matplotlib-users

[Matplotlib-users] Plotting points on images - axes problems

[Robert S. <si...@us...>]

Hi,

Using matplotlib 0.87.2, I've been trying to plot points on top of an 
image.  The image without points fills axes of the extent requested, 
but using plot to add a point on top of the image changes the axes 
lengths and gives unwanted white margins around the edges.  Here's an 
example.  Any help would be greatly appreciated!

Bob Simpson

from pylab import *

# Sample image.
image = rand(12,6)

# This choice for extent works fine... It produces no white margins.
#extent = [-80, 60, -60, 40]

# This choice gives unwanted white margins,
#   except when no point is plotted.
extent = [-80.,64., -74.,48.]

ax1 = axes()
ax1.im = imshow(image, origin='lower', extent=extent)

# Plot point on image.
hold(True)
ax1.plot([0.0],[0.0],'wo')

show()

Re: [Matplotlib-users] Plotting points on images - axes problems

[Eric F. <ef...@ha...>]

Bob,

Try doing

b = axis()
ax1.plot([0.0],[0.0],'wo')
axis(b)

That saves the axis range set by imshow and restores it after the call 
to plot.

Eric

Robert Simpson wrote:
> Hi,
> 
> Using matplotlib 0.87.2, I've been trying to plot points on top of an 
> image.  The image without points fills axes of the extent requested, but 
> using plot to add a point on top of the image changes the axes lengths 
> and gives unwanted white margins around the edges.  Here's an example.  
> Any help would be greatly appreciated!
> 
> Bob Simpson
> 
> from pylab import *
> 
> # Sample image.
> image = rand(12,6)
> 
> # This choice for extent works fine... It produces no white margins.
> #extent = [-80, 60, -60, 40]
> 
> # This choice gives unwanted white margins,
> #   except when no point is plotted.
> extent = [-80.,64., -74.,48.]
> 
> ax1 = axes()
> ax1.im = imshow(image, origin='lower', extent=extent)
> 
> # Plot point on image.
> hold(True)
> ax1.plot([0.0],[0.0],'wo')
> 
> show()
> 
> 
> 
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Re: [Matplotlib-users] Plotting points on images - axes problems

[John H. <jdh...@ac...>]

>>>>> "Eric" == Eric Firing <ef...@ha...> writes:

    Eric> Bob, Try doing

    Eric> b = axis() ax1.plot([0.0],[0.0],'wo') axis(b)

    Eric> That saves the axis range set by imshow and restores it
    Eric> after the call to plot.

You can also turn on an off autoscaling

  ax.set_autoscale_on(False)

JDH