Friday, February 17, 2012

Create a PDF document containing dynamic images

For a current project we had the requirement to publish a more or less "glossy" PDF document containing all information about a certain object. One of the bits of information was...an image. 
The first trial we used the APEX_WEB_SERVICE.BLOB2CLOBBASE64 function to convert a Blob to clob with base64 encoding. In the RTF Template (used in Word with the BI Publisher plugin) you can reference it using this code :

<fo:instream-foreign-object content-type="image/jpg">
<xsl:value-of select=".//PHOTO"/>
</fo:instream-foreign-object>
(where PHOTO is the alias of the clob column).

This works....until you're using a slightly bigger picture than a tiny thumbnail. In that case you hit the 32K limit per report column. Although Marc Sewtz (from the APEX Development Team) sort of "promised" to lift this limit in his blogpost of Jun 13 2008 (!) (http://marcsewtz.blogspot.com/2008/06/one-question-about-pdf-printing-feature.html), it is still the current limit.

The workaround - or other approach - is to call an image with a http request in the report definition. Therefore you have to create your own "display_image" procedure that downloads the image. Be sure to grant execute on this procedure to APEX_PUBLIC_USER or ANONYMOUS (depending on your configuration), and modify the WWV_FLOW_EPG_INCLUDE_MOD_LOCAL function when you're using the EPG (see http://daust.blogspot.com/2006/04/xe-calling-stored-procedures.html).

Next, change your query with a call to that procedure:
apex_application.get_g_base_href||'#OWNER#.DISPLAY_IMAGE?P_OBJECT_ID'||ID as IMAGE_URL 

In your RTF Template you have to embed a dummy image and set the "Alt-Text" (via Size in the Image menu) to url:{IMAGE_URL}.

The first result was : It works for HTML output and Excel output...but not for Word (RTF) or PDF. Why this difference? No idea!
My setting was like this:
So the "POPULAIRE_NAAM" was visible on the report, but the image wasn't. And everything else below - all 8 ROWSETS - were visible as well. FYI: The grey border above with the text "Geen afbeelding beschikbaar" is an image itself, so it's not some image missing from this blogpost ;-)
After a lot of trial and error and Googling around, I called to the OTN Forum for help (see thread here : https://forums.oracle.com/forums/thread.jspa?threadID=2347610&tstart=0). After a few hours Carsten Czarski of Oracle Germany pointed to an elaborated example he put on the web - a long time ago, looking at the screen prints : http://www.oracle.com/webfolder/technetwork/de/community/apex/tipps/pdf-dyn-images/index.html. Because it was in German, it never popped up in my Google search..while all the components where in there! So I created a very very simple example to mimic his case. And then the image did show up!
So what did I do wrong?

It seems that the [for-each ROWSET1_ROW] loop must be defined before the image (although in my case that rowset always contains just one entry). It didn't matter for the "POPULAIRE_NAAM" field, but it did for the image (in Word/PDF, not in HTML/Excel).
So the correct setting is:

and now the PDF can contain images of any size....