Problem: Height and Width properties not honored with IDibExporter, ITiffExporter, and IJpegExporter
If PixelBounds is set before Width and Height, then it is ignored, and Width and Height are honored.
When Height and Width properties of the exporter are set using Visual Basic, they will be ignored if you subsequently set the IExporter::PixelBounds property.
Solution or Workaround
The export objects provide several methods to specify output size.
Specify either IExporter::PixelBounds or Height and Width but not both.