Bug report

Bug summary
Rasterizing the marker collection results in a large file size as compared to rasterizing the whole axes. See the example below:

Code for reproduction

importmatplotlib.pyplotaspltimportnumpyasnpdata=np.random.rand(100,100)fig1,ax1=plt.subplots()ax1.plot(data,'o',rasterized=True)fig1.savefig('rasterizing_markers.pdf')fig2,ax2=plt.subplots()ax2.set_rasterized(True)ax2.plot(data,'o')fig2.savefig('rasterizing_axes.pdf')

Actual outcome
rasterizing_axes.pdf is around 123 KB and rasterizing_markers.pdf is around 447 KB! (the only difference in those two files is that rasterizing_markers.pdf has spines, ticks and tick labels in vector format)

Expected outcome
Expecting that both files will have similar size. I am sure that the difference is not because of the embedded fonts (If I changedata = np.random.rand(100, 100) todata = np.random.rand(10, 10), the file size for rasterizing_markers.pdf is 23 KB so that rules out the role of embedded fonts in explaining the ~300 KB difference).

Matplotlib version

• Operating system: MacOS
• Matplotlib version: 3.0.3
• Matplotlib backend (print(matplotlib.get_backend())):
• Python version: 3.7
• Jupyter version (if applicable):
• Other libraries: