PDF Optimizer: What is'Optimize compression of page regions based on color content'?

[Danielle_Walton@adobeforums.com]

Here is my story...

I received a pdf of an ad that was designed in InDesign. To use with our Ad Management system our workflow is to flatten transparency when we receive ads from InDesign to ensure proper reproduction... here is where my dilemma begins.

The ad was taken into Acrobat 7.0, and using pdf optimizer it was flattened, uploaded into our Admanager and released. Well, the optimization of the ad turned it RGB (it came in CMYK), and I think we all know how well RGB images/art reproduced when separated CMYK.

To troubleshoot this problem I took the original version of the ad opened it and checked the optimization settings that were selected. I noticed that the button 'Optimize compression of page regions based on color content' (on the scanned pages menu) was checked and was the only difference from the Optimization presets that were previously created.

So... I then took other ads and optimized them with the above button checked, nothing happened... all of the ads stayed CMYK.

Next I created my own InDesign document and exported it out using the different PDF export presets (Press Quality and x1a).

When I optimized the Press Quality pdf everything turned RGB... when I ooptimized the x1a pdf it stayed CMYK.

So I guess my question is... What does the 'Optimize compression of page regions based on color content'do? And what is it for?

Thanks for your responses!

[Jon_Bessant@adobeforums.com]

I would *guess* it takes all the content and attempts to fit into
smaller colour spaces based upon the colour arrays? This *might* result
in a mixture of CMYK, indexdedCMYK, RGB etc., etc.

However, this option should not generally be used for print based PDFs
since it's all about optimising for pre-OCR ....

Jon