How to plot blurred points in Matplotlib

Question

As the question says, I'm looking for a way to plot blurred points using Matplotlib. I don't want to plot a set of points and then apply a filter to blurry the whole image. Instead of it, I would like to plot a set of points, each of them with an associated level of blur.

Thank you in advance.

Answer 1

Here's another work around. You can display an image at each location instead of a marker using a BboxImage. That way you can blur or manipulate the image any way you want. This tutorial has more about BboxImages.

import matplotlib.pyplot as plt
from scipy import ndimage
from matplotlib.image import BboxImage
from matplotlib.transforms import Bbox, TransformedBbox
import numpy as np

# Create and save an image with just a marker in it
fig1 = plt.figure()
ax1 = fig1.add_subplot(111)
ax1.plot(0.5,0.5,'*',ms=200)
ax1.set_ylim(0,1)
ax1.set_xlim(0,1)
plt.axis('off')
fig1.savefig('marker.png')

# Read in the same marker image
marker = plt.imread('marker.png')

# New figure and data
fig2 = plt.figure()
ax2 = fig2.add_subplot(111)
x = 8*np.random.rand(10) + 1
y = 8*np.random.rand(10) + 1
sigma = np.arange(10,60,5)

# Blur the marker and image plot the blurred image at each data point. 
for xi, yi, sigmai in zip(x,y,sigma):
    markerBlur = ndimage.gaussian_filter(marker,sigmai) # Blur the marker image

    # Create an BboxImage for the blurred marker and add it to the plot. 
    bb = Bbox.from_bounds(xi,yi,1,1)  
    bb2 = TransformedBbox(bb,ax2.transData)
    bbox_image = BboxImage(bb2,
                           norm = None,
                           origin=None,
                           clip_on=False)

    bbox_image.set_data(markerBlur)
    ax2.add_artist(bbox_image)

ax2.set_xlim(0,10)
ax2.set_ylim(0,10)
plt.show()