Creating large PDFs from PNG files

I've been looking at the various QPDFL functions and I'm not sure what the best approach is for this; hopefully someone has done this before and has some pointers...

I have a potentially large number of PNG files (too large to do this all in memory, so looking at a way to use DA functions for all or part of the process) that I need to convert into a single PDF file, where each page of the PDF is simply one of the PNGs.

My general thinking is to do something like this:

For each PNG:
> NewDocument
> NewPage
> InsertPages (one page)
> AddImageFromFile
> DrawImage (onto new page)
> SaveToFile (single page PDF)

Then, use DA functions (to do the merging on disk)...

> DAOpenFile (output file)

For each single-page PDF:
> DANewPage (add to output file)
> DAOpenFile (input file)
> DACapturePage (from input file)
> DANewPage (in output file)
> DADrawCapturedPage (on output file)
> DACloseFile (input file)

> DAClose File (output file)


I haven't actually tried this yet--it seems like it would work, but it also seems a bit clunky. So, is there a better way?

Thanks for the quick reply!

Could you elaborate a bit on your comments?

1) When you say I can live without the DA functions, my purpose of using them was to minimize memory usage by creating the full output file (that contains all the pages) on disk only. Are you saying I can achieve this without using DA functions?

2) Maybe this is what you're referring to by "free then a new create", but please explain exactly what I'm freeing and creating (and exactly what functions I should be calling).

3) I did find the C# sample for doing this, but since it appears to be doing everything in memory, I didn't think it would work for me. Maybe there is something I'm not understanding about the "high level" functions--would using them not result in a "completely in-memory" version of my output PDF?

4) Finally, on a related note, is it possible to "mix" DA and non-DA functions? In other words, could I do a non-DA CapturePage and use the CaptureID in a call to DADrawCapturedPage? (I believe the answer is no, but just making sure).


Edited by Eric24 - 29 Jun 09 at 4:44AM

As Ingo mentioned, the DA and non-DA functions will not work together at all. You could try using the MergeFileListFast function if you wanted to try to do this in memory, however, if you're dealing with PDFs over 50-100 MB, this can be quite slow due to the nature of PDFs.