John,
As long as .Stretch is 0 (and it will be 0 when instantiating the VFP baseclass Image) setting the .Picture property of the object will cause it's .Height and .Width to be set based on the image file. You can of course change them after it's loaded, but the code Sergey posted works just fine for this problem.
>The oPic.Height / oPic.Width properties concern the display height and width. To find the pixel dimensions without going to a 3rd party utility, try using the PictureClip control PICCLP32.OCX. The documentation refers to 'bitmaps' but jpegs work as well.