Pixel = EMUs * Resolution / 914400; where "Resolution" is resolution of your screen. e.g. 96 dpi.
<p:cSld> common slide data element <p:sp> shapes element <p:nvSpPr> Each shape element contains a set of non-visual properties <p:nvPr> non-visual properties <p:ph> a placeholder The placeholder element is empty but does have several possible attributes. It is using the "idx" and "type" attributes that the shapes are linked across the three slide types.