CFPDF - Issues When Using Transparent Images as a Watermark

I saw an interesting question on the abode forums yesterday, about problems with watermarks and cfpdf. The issue involved using transparent png's or gif's as a watermark. The transparent parts of the image seem to be rendered as white, instead of maintaining their transparency.


As I was curious, I tried a number of different things but nothing seemed to work except a bit of iText magic. The work-around comes from an adaptation of two great iText examples. The code is very simple. It uses PdfGState to set the watermark to 50% opacity, but you can change that (and other properties like blendMode) as well.

If anyone knows a way around this issue (using cfpdf or ddx), I would love to hear it.


Update July 13,2009: This issue appears to be fixed in CF9 beta.


iText Example Java Source:

• AddWatermarkPageNumbers
• WatermarkExample
  

<!---
Add a centered watermark with 50% opacity
--->
<cfscript>
savedErrorMessage = "";

fullPathToInputFile = ExpandPath("mySourceFile.pdf");
fullPathToWatermark = ExpandPath("myTransparentImage.png");
fullPathToOutputFile =  ExpandPath("mySourceFile_Watermarked.pdf");

try {
    // create PdfReader instance to read in source pdf
    pdfReader = createObject("java", "com.lowagie.text.pdf.PdfReader").init(fullPathToInputFile);
    totalPages = pdfReader.getNumberOfPages();

    // create PdfStamper instance to create new watermarked file
    outStream = createObject("java", "java.io.FileOutputStream").init(fullPathToOutputFile);
    pdfStamper = createObject("java", "com.lowagie.text.pdf.PdfStamper").init(pdfReader, outStream);

    // Read in the watermark image
    img = createObject("java", "com.lowagie.text.Image").getInstance(fullPathToWatermark);

    // Use PdfGState to change fill,blendMode, etcetera as needed
    gState = createObject("java", "com.lowagie.text.pdf.PdfGState").init();
    gState.setFillOpacity(0.5);

    // adding content to each page
    p = 0;
    while (p LT totalPages) {
        p = p + 1;
        // Prepare to place image on OVERcontent
        content = pdfStamper.getOverContent( javacast("int", p) );
        // Only needed if you are changing the opacity, blending, etcetera ..
        content.setGState(gState);

        // Center the watermark. Note - using deprecated methods for CF8/iText 1.4 compatability
        rectangle = pdfStamper.getReader().getPageSizeWithRotation( javacast("int", p) );
        x = rectangle.left() + (rectangle.width() - img.plainWidth()) / 2;
        y = rectangle.bottom() + (rectangle.height() - img.plainHeight()) / 2;
        img.setAbsolutePosition(x, y);

        content.addImage(img);
        WriteOutput("Watermarked page "& p &"<hr>");
    }

    WriteOutput("Finished!");
}
catch (java.lang.Exception e) {
    savedErrorMessage = e;
}
// closing PdfStamper will generate the new PDF file
if (IsDefined("pdfStamper")) {
    pdfStamper.close();
}
if (IsDefined("outStream")) {
    outStream.close();
}
</cfscript>

<!--- show any errors --->
<cfif len(savedErrorMessage) gt 0>
    ERROR - Unable to create document
    <cfdump var="#savedErrorMessage#">
</cfif>