Generic subroutines for inserting PNG files in PostScript

Hi, I have a generic subroutine for inserting JPGs in PostScript:

/insertjpg {
     /ypix exch def  %height of jpeg in pixels
     /xpix exch def  %width of jpeg in pixels
     /ymeas exch def %height of jpeg in measured distance, WITHOUT unit of measurement
     /xmeas exch def %width of jpeg in measured distance, WITHOUT unit of measurement
     /ypos exch def  %y-position of jpeg
     /xpos exch def  %x-position of jpeg
     /jpg exch def   %full path/filename of jpeg, enclosed in parentheses

     gsave
     xpos ypos translate
     xmeas ymeas scale
     /DeviceRGB setcolorspace % How color values will be interpreted
     << % Start image dictionary
          /ImageType 1
          /Width xpix % Dimensions of source image
          /Height ypix
          /BitsPerComponent 8
          /Decode [0 1 0 1 0 1] % Decode color values in normal way
     /ImageMatrix [xpix 0 0 ypix neg 0 ypix] % Map unit square to source
     /DataSource jpg (r) file /DCTDecode filter
     >> % End image dictionary
     image

     xpos neg ypos translate
     xmeas pt ymeas pt scale
     grestore

} def

I'm trying to adapt the following code so I can insert PNGs, but I keep getting the error %%[ Error: ioerror; OffendingCommand: imageDistiller ]%%

/insertpng {
     /ypix exch def  %height of png in pixels
     /xpix exch def  %width of png in pixels
     /ymeas exch def %height of png in measured distance, WITHOUT unit of measurement
     /xmeas exch def %width of png in measured distance, WITHOUT unit of measurement
     /ypos exch def  %y-position of png
     /xpos exch def  %x-position of png
     /png exch def   %full path/filename of png, enclosed in parentheses

     gsave
     xpos ypos translate
     xmeas ymeas scale
     /DeviceRGB setcolorspace % How color values will be interpreted

     << % Start image dictionary
          /ImageType 1
          /Width xpix % Dimensions of source image
          /Height ypix
          /BitsPerComponent 8
          /ImageMatrix [xpix 0 0 ypix neg 0 ypix] % Map unit square to source
          /Decode [0 1 0 1 0 1] % Decode color values in normal way
          %/Interpolate true
          /ImageMask true
          /DataSource png (r) file
               %/ASCII85Decode filter
          << /Predictor 15 /Columns xpix /Colors 3 /BitsPerComponent 8 >> /FlateDecode filter
      >>
     image

     xpos neg ypos translate
     xmeas pt ymeas pt scale
     grestore
} def

I appreciate any help you can offer.