Make image transparent and text opaque

Hey,

I'm very new to Quick PDF Library and I'm not yet having a grip to the vast set of functions.

I have a PDF that comes from Nuance OCR. It has one image per page and invisible but selectable text (the OCR text). Nuance calls this "text over image". I'd like to do the following:

- Make the image transparent (about 20%)
- Make the text visible/opaque

The reason for this is that I want to check the quality of the OCR by being able to directly compare the recognized text to the image. That's why I'd like to see the text.

I've looked through the documention but I haven't found a way to directly manipulate the text or the image transparency. All the methods I found just seem to work "subsequently". Does this mean I have to build a completely new PDF document by copying the contents of my original PDF, image per image, text block per text block, to be able to set text color or image transparency?

I hope not... ;-)

Thanks in advance for enlighting hints.

Georg

Hi Ingo,

thank you very much for your answer!

I experimented with the layers/content streams and I got weird results.

ContentStreamCount returns 2, as expected.

When I delete Stream 1, the resulting PDF seems completely empty. No image, no selectable text.

When I delete Stream 2, BOTH are still visible.

In both cases, the size of the resulting PDF is very near to the original, despite one layer should have been removed.

Doesn't "DeleteContentStream" do what it is supposed to do? Or am I misunderstanding some fundamental concepts?

I haven't found more fitting methods in "Content Streams and Optional Content Groups" help page.

Btw: I do not want to delete layers, I'd like to manipulate them as described in my initial post.

Best regards,
Georg