fo:external-graphic

Hi All,

I use the following code in my xsl to display a image,
      <xsl:element name="fo:external-graphic">
       <xsl:attribute name="src">images/pdf/logo.gif</xsl:attribute>
       <xsl:attribute name="content-width">123px</xsl:attribute>
       <xsl:attribute name="content-height">31px</xsl:attribute>
       <xsl:attribute name="width">auto</xsl:attribute>
       <xsl:attribute name="height">auto</xsl:attribute>
       <xsl:attribute name="scaling">auto</xsl:attribute>
     </xsl:element>
The content-width and content-height are the same as the original image. But when I print out the pdf page, the image is much bigger than the original one. It seems all attributes of the element did not work, except the src.

Can anybody tell me how can I get a image with the original size?

Thanks,

Hong Jiang