PDFlib --pixels?

Hello, I'm developing a web app, that needs to generate a PDF file. The "background" of the PDF will be a high resolution image (300dpi). and I calculate the scaling factor from the resolution of the image. $dpi_x =PDF_get_value($p,"resx",$image); $dpi_y =PDF_get_value($p,"resy",$image); /*calculate scaling factors from the dpi values */ if ($dpi_x >0 && $dpi_y >0){ $scale_x =(72.0)/$dpi_x; $scale_y =(72.0)/$dpi_y; Now, I have the pixel coordenates of the text that will be written (I have the text, color, font, textX and textY). This coordenates were taken from the way it looked on a 72 dpi image. How can I get the cordenates that I sould use on the PDF??.. because if I use the same coord I have, it places the text waaaay out of where it's supposed to be. Please advice!. Oscar.-