How to export grayscale image as grayscale in PDF?

[mwenz]

But you are at least triple-processing anyway.

Your scanner when scanning to grayscale is applying a dot gain profile and likelya gamma curve to the image.
You bring it into Xara wherein it is converted to an RGB image.
Depending on what type of PDF you are producing, you are possibly processing it again at PDF output time. If you are using a CMYK profile, it is now being converted to CMYK. Yet another processing.
In acrobat, converting it to grayscale yet again is another processing.

Each time it is processed, you are changing the pixels. Not a good work-flow.

I have attached the test image from the Wiki page. I placed it into XDP as an untouched, "original" RGB image. I exported to PDF. Whether I use a CMYK or an RGB output profile doesn't matter, the result is identical. I then used the process in Acrobat I described.

In short, scanning to gray, etc., has only detriment--there is no reason to do so if using an application like an Xara product.



Mike