Years ago I came across a technique in one of the PhotoShop books at the time. It had to do with scanning images that had already been processed for printing. I have searched all of my reference material and cannot find it. It was relatively easy from what I remember only one part is escaping me. The procedure called for the printed image to be placed at an angle on the scanner. It was then scanned at a very high resolution (1200 dpi), Once the scan was complete, the image would then be rotated back to a 90 degree angle. This is the step that is missing-but I seem to think it was to use the Gaussian Blur (possibly the unsharp mask) but am unsure of this. The image could be then cropped and the resolution dropped down to 300-600 dpi, Does this ring any bells with anyone? Anyone have any ideas?

Run the Median filter on the individual channels. Usually the Blue channel will need the highest radius, then Green, with Red typically needing the lowest.

Then follow that with a GBlur using the same radius settings on each channel.

If it's a color picture, you might want to try converting to LAB and blurring the A&B channels either instead of the above or as a preliminary step. It should allow you to use a lower radius setting thereby retaining more detail.

Also look around on this site for FFT tutorials. It's a filter that does amazing things with repeating patterns such as prescreened originals.

Regards,

Michael