python - Matplotlib scatter plot - Remove white padding

Question

I'm working with matplotlib to plot a variable in latitude longitude coordinates. The problem is that this image cannot include axes or borders. I have been able to remove axis, but the white padding around my image has to be completely removed (see example images from code below here: http://imgur.com/a/W0vy9) .

I have tried several methods from Google searches, including these StackOverflow methodologies:

Remove padding from matplotlib plotting

How to remove padding/border in a matplotlib subplot (SOLVED)

Matplotlib plots: removing axis, legends and white spaces

but nothing has worked in removing the white space. If you have any advice (even if it is to ditch matplotlib and to try another plotting library instead) I would appreciate it!

Here is a basic form of the code I'm using that shows this behavior:

import numpy as np
import matplotlib
from mpl_toolkits.basemap import Basemap
from scipy import stats

lat = np.random.randint(-60.5, high=60.5, size=257087)
lon = np.random.randint(-179.95, high=180, size=257087)
maxnsz =  np.random.randint(12, 60, size=257087)

percRange = np.arange(100,40,-1)
percStr=percRange.astype(str)
val_percentile=np.percentile(maxnsz, percRange, interpolation='nearest')  

#Rank all values
all_percentiles=stats.rankdata(maxnsz)/len(maxnsz)
#Figure setup
fig = matplotlib.pyplot.figure(frameon=False, dpi=600)
#Basemap code can go here

x=lon
y=lat

cmap = matplotlib.cm.get_cmap('cool')


h=np.where(all_percentiles >= 0.999)
hl=np.where((all_percentiles < 0.999) & (all_percentiles > 0.90))
mh=np.where((all_percentiles > 0.75) & (all_percentiles < 0.90))
ml=np.where((all_percentiles >= 0.4) & (all_percentiles < 0.75))
l=np.where(all_percentiles < 0.4)

all_percentiles[h]=0
all_percentiles[hl]=0.25
all_percentiles[mh]=0.5
all_percentiles[ml]=0.75
all_percentiles[l]=1

rgba_low=cmap(1)
rgba_ml=cmap(0.75)
rgba_mh=cmap(0.51)
rgba_hl=cmap(0.25)
rgba_high=cmap(0)

matplotlib.pyplot.axis('off')

matplotlib.pyplot.scatter(x[ml],y[ml], c=rgba_ml, s=3, marker=',',edgecolor='none', alpha=0.4)
matplotlib.pyplot.scatter(x[mh],y[mh], c=rgba_mh, s=3,     marker='o', edgecolor='none', alpha=0.5)
matplotlib.pyplot.scatter(x[hl],y[hl], c=rgba_hl, s=4, marker='*',edgecolor='none', alpha=0.6)
matplotlib.pyplot.scatter(x[h],y[h], c=rgba_high, s=5, marker='^', edgecolor='none',alpha=0.75)

fig.savefig('/home/usr/code/python/testfig.jpg', bbox_inches=0, nbins=0, transparent="True", pad_inches=0.0)
fig.canvas.draw()

Answer 1

The problem is that all the solutions given at Matplotlib plots: removing axis, legends and white spaces are actually meant to work with imshow.

So, the following clearly works

import matplotlib.pyplot as plt

fig = plt.figure()
ax=fig.add_axes([0,0,1,1])
ax.set_axis_off()

im = ax.imshow([[2,3,4,1], [2,4,4,2]], origin="lower", extent=[1,4,2,8])
ax.plot([1,2,3,4], [2,3,4,8], lw=5)

ax.set_aspect('auto')
plt.show()

and produces

But here, you are using scatter. Adding a scatter plot

import matplotlib.pyplot as plt

fig = plt.figure()
ax=fig.add_axes([0,0,1,1])
ax.set_axis_off()


im = ax.imshow([[2,3,4,1], [2,4,4,2]], origin="lower", extent=[1,4,2,8])
ax.plot([1,2,3,4], [2,3,4,8], lw=5)

ax.scatter([2,3,4,1], [2,3,4,8], c="r", s=2500)

ax.set_aspect('auto')
plt.show()

produces

Scatter has the particularity that matplotlib tries to make all points visible by default, which means that the axes limits are set such that all scatter points are visible as a whole.

To overcome this, we need to specifically set the axes limits:

import matplotlib.pyplot as plt

fig = plt.figure()
ax=fig.add_axes([0,0,1,1])
ax.set_axis_off()

im = ax.imshow([[2,3,4,1], [2,4,4,2]], origin="lower", extent=[1,4,2,8])
ax.plot([1,2,3,4], [2,3,4,8], lw=5)

ax.scatter([2,3,4,1], [2,3,4,8], c="r", s=2500)

ax.set_xlim([1,4])
ax.set_ylim([2,8])

ax.set_aspect('auto')
plt.show()

such that we will get the desired behaviour.