imread and imshow reduce the quality of image printed to powerpoint

Hi all

I am reading some plots saved as jpg. already with an increase size to have a better resolution ( 1200x1000) and I am reading them using imread and imshow to print them to powerpoint using pptpop() function.

but what I see is that the quality of the images really reduces, is there any solution to this problem ? I think part of the reduction comes from reading the image and part is by saving it to ppt