iText getDpiX() returns zero and cannot maintain originality in .png

[Krishna Chaitanya Reddy Balam]

I am trying to print a .png file into pdf and I want the same clarity inside the pdf.
I was trying to
png.scalePercent(72f / jpg.getDpiX() * 100);
but getDpiX() returns zero.
Is there any way to keep the images as it is in pdf rather than default dpi.
The images are large in number and I cannot do something like
png.scalePercent(75);

Please provide me a mechanism where I can preserve the originality of any .png image on pdf.