Finding optimal colours for separating a scanned print

Discuss digital image processing techniques and algorithms. We encourage its application to ImageMagick but you can discuss any software solutions here.
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pipe
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Finding optimal colours for separating a scanned print

Post by pipe »

I scanned some printed material at a high resolution recently, and I want to reverse the halftoning.

I know how to do this using an FFT, but I was thinking a bit about the color channels. It seems to me that I would want to do this in a CMYK colorspace, but is there a way to extract the exact colors for C, M and Y that was used when printing, and after it has passed through my scanned? I'm pretty sure that the cyan used for printing wont come out as #00FFFF after printing on random paper, coated, and then scanned.

My reasoning is this: The scanned print consists of a lot of colored dots, mostly cyan, magenta and yellow. After having been converted to some kind of RGB by my scanner, is there a way to extract the RGB triplets for these primaries, then feed these to ImageMagick and say "Hey, convert the image to CMYK. Here are the XYZ points for C, M and Y.".

Does this make any sense? Can it be done with color profiles? I know very little about these, but I do know a little about vector algebra, maybe there's a "-distort" but for color channels that can be abused.

snibgo
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Re: Finding optimal colours for separating a scanned print

Post by snibgo »

In principle:
- Ensure your scanned (RGB) file has embedded the correct profile for your scanner.
- Convert it to the profile for the printer. The profile should account for the type of paper etc.
The file is now CMY or CMYK. When printed on the same printer, with the same paper etc, it will look exactly like the print you scanned.
snibgo's IM pages: im.snibgo.com

pipe
Posts: 28
Joined: 2013-04-09T08:32:37-07:00
Authentication code: 6789

Re: Finding optimal colours for separating a scanned print

Post by pipe »

I have not printed them myself, so I have no idea about the printer/paper profile, that's my problem here. I should be able to find a color profile for the scanner, it seems pretty high-end.

EDIT: I'm not trying to print anything either, I just want to analyze and improve the quality of the scanned prints.

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