PowerPoint add transparent images

[nets-rac]

Hi,

I want to add an image to a powerpoint presentation with c#. That works
fine if the image has no transparent background. If I use an image with
a transparent background the pixels in the image are very square edged
especially if the image contains text.

is there a possibility to solve this problem?

By the way...I use following method to add the picture:

slide.Shapes.AddPicture(path, MsoTriState.msoFalse,
MsoTriState.msoTrue, 235, 185, -1, -1);
Thanks