How to save the background transparent for PowerPoint presentation

[masu]

Hello,

How can I save the background of a screenshot as transparent for a powerpoint presentation?
The image format should be in lossless PNG

[mouser]

can you be a little more specific about what you mean by "background"?

[masu]

e.g. I use a 3d CAD program. The background is blue, the model is on the foreground.

blue should be replaced by transparent colour.

[mouser]

while i could add such features to screenshot captor, the easiest and most flexible approach is to configure a graphics program (like paint.net) to launch from screenshot captor and use that to make regions transparent.

[masu]

thanks for your info.
but maybe this could also be possible with Screenshot Captor.