About pdf by subplot

Dear all

I have a question about pdf created by subplot. I wrote a code like attached in bottom.
Two pdf are created by the code as ’a.pdf’ and ‘b.pdf’. I converted these pdf to pptx by acrobat for presentation.
However, the first left image in ‘a.pdf’ is recognized as background by powerpoint and I cannot handle this image…
In b.pdf, the first image is blank and it is recognized as background, so I can handle the second and the third images in powerpoint…

why I use the pdf is that the images are clearer than jpg or something like that. however I have to
insert the blank image when I use the subplot…Can I escape this hassle anyway?

thank you
morisitaa


import matplotlib.pyplot as plt
import numpy as np

a=np.random.random((10,10))
b=np.random.random((20,20))

plt.figure(figsize=(10,5))
plt.subplot(121)
plt.imshow(a)
plt.subplot(122)
plt.imshow(b)
plt.savefig(‘a.pdf’)
plt.show()

plt.figure(figsize=(15,5))
plt.subplot(131)
plt.subplot(132)
plt.imshow(a)
plt.subplot(133)
plt.imshow(b)
plt.savefig(‘b.pdf’)
plt.show()