Scatter plotting a bunch of points while specifying the colour of each point, then changing the axes limits so none of the points are visible, and then saving the result to a PDF, results in a file just as big as if the points were all visible within their default axes limits. This doesn't seem to happen if the colour arg isn't passed to scatter(). I haven't tried, but specifying other kinds of point specific attributes, like size, might also trigger the problem . Also, I haven't tried any of the other vector backends, but they may be affected as well.

This came out of #2423.

Example code:

import numpy as np
x = np.random.random(20000)
y = np.random.random(20000)
c = np.random.random(20000)

figure()
scatter(x, y)
pyplot.savefig('scatter.pdf')
xlim(2, 3) # move axes away for empty plot
pyplot.savefig('scatter_empty.pdf')
'''
file sizes in bytes:
scatter.pdf:       324187
scatter_empty.pdf:   6617
'''
figure()
scatter(x, y, c=c)
pyplot.savefig('scatter_color.pdf')
xlim(2, 3) # move axes away for empty plot
pyplot.savefig('scatter_color_empty.pdf')
'''
file sizes in bytes:
scatter_color.pdf:       410722
scatter_color_empty.pdf: 413541
'''