Images quality

Hi all,

I have a image quality problem, all images I use in PDF::API2 appear
blurred, the images are all 72DPI.

The original blurred image appear bigger so I scale to get original
size, I had try many image formats and all ways have a less quality
than the original.

So, what specifications needs to have the image or what options are
required to get original image quality?

Thanks in advance.