Html parses can't handle png-images if default image format is jpg

[Bellfalasch]

In the <xsl:if test="$source-image"> on row 150 of the html.xsl we need to make sure that the $format param is used for the stk:image-create call. Otherwise transparent PNG images will always turn into opaque JPEG-images if Theme default image format is set to be JPG.

This little code inside that if check current file ending and forces "png" if original image is png. In the call-template later add <xsl:with-param name="format" select="$format" />.

<xsl:variable name="format">
    <xsl:choose>
        <xsl:when test="stk:file.get-extension( $source-image/binaries/binary[@label = 'source']/@filename ) = 'png'">
            <xsl:value-of select="'png'"/>
        </xsl:when>
        <xsl:otherwise>
            <xsl:value-of select="$stk:default-image-format"/>
        </xsl:otherwise>
    </xsl:choose>
</xsl:variable>