Black patch codes and even blacker patch codes

Black patch codes and even blacker patch codes

Postby aadslingerland » Fri Apr 13, 2012 3:15 am

Ladies and Gents,

I’m facing a strange issue regarding black patch codes and black bar codes in combination with scanning in color mode. The point is that patch code and bar code pages have been prepared on two different printers. Just white paper with black patch codes and black bar codes. Just black, I thought. . . .

The one printer produces pages with mat black. The kind of black that is not so deep black as possible but remains black even if looked upon from a 45 degree angle.

The other printer produces pages with a crisp kind of black. It’s really black when viewed from about a 90 degree angle. But when viewed from a 45 degree angle there shiny particles appear. Like viewing a brightly black polished car.

So what’s the point you might wander? The point is that these patch code and bar code pages are being used in batches that are set up for color scanning. I did customize VRS to use background color detection and background color suppression to minimize the amount of megabytes stored and transported.

The quality of the final batch code and bar code pages, after being processed by VRS, is however rather bad. The resulting images of the patch code pages of type “mat black” are OK. The resulting images of the patch code pages of type “crisp black” are almost worthless and result in too many misinterpreted bar codes.

For clarity’s sake I include two partial images here. . .

mat_black_after_scan.jpg
(23.96 KiB) Downloaded 513 times


crisp_black_after_scan.jpg
(54.41 KiB) Downloaded 506 times


The short term solution is, of course, instruct the customer to use the type of printer that produces mat black and leave. However, this would not satisfy my intellectual and professional needs :wink: . And I’m sure the same issue will pop up somewhere else.

So I’m digging into this black hole. Not only for the fun of it but also to have a better long term answer for this and future customers. After composing this message and posting it I’m going to contact the printer vendor(s) and ask advice about laser printer toner cartridges.

Let me further describe the environment where this all happens:
Kofax Capture 8 SP5 with VRS 4.1.
Kodak i620 scanners.
Scanning in 300 DPI Color.
VRS color detection enabled.
VRS background color suppression.

What would you do?
With Regards, Aad Slingerland
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Re: Black patch codes and even blacker patch codes

Postby russell@centuryc.com » Fri Apr 13, 2012 11:14 am

aadslingerland wrote:But when viewed from a 45 degree angle there shiny particles appear.


I think the operative word here is "particles". When VRS converts an image to bitonal, it looks for variations and highlights them. That way if something is written in a shaded area, the "blacker then black" will be outlined so it's readable.

I suspect the angle between the light source and the camera in that scanner brings out how uneven the black is. VRS is just highlighting the variations.

It's possible that running a calibration on the scanner could fix that hiding all the variations by rendering everything as black instead of shades of dark gray. Likewise adjusting the image would help. but that would affect how the color images are rendered as well.
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Re: Black patch codes and even blacker patch codes

Postby dkekesi » Mon Apr 16, 2012 12:45 am

I would say that the bar code does not meet specifications. Bar code standards do not only define how each bar looks like, but they usually include printing standards as well. This defines contrast requirements that - in your particular case - are not met. Take a look at this: http://www.lvs-inc.com/ContentPDFS/ANSIOverview.PDF
Best Regards,

Daniel Kekesi
DocSoft Hungary
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Re: Black patch codes and even blacker patch codes

Postby rpapa » Mon Apr 16, 2012 7:42 am

sometimes, I see patch codes scanned like this in b&w if advanced clarity is turned on.

I'm not sure how to change it if scanning in color.
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Re: Black patch codes and even blacker patch codes

Postby aadslingerland » Tue Apr 17, 2012 2:43 am

rpapa wrote:sometimes, I see patch codes scanned like this in b&w if advanced clarity is turned on.


I'm going to try out some VRS options... Turn one on, scan, compare, turn one off, scan, compare, etc...
With Regards, Aad Slingerland
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Re: Black patch codes and even blacker patch codes

Postby rpapa » Tue Apr 17, 2012 4:28 am

sorry, I meant if advanced clarity is off when scanning in b&w, turning it on, makes it look better, like you're b&w sample
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Re: Black patch codes and even blacker patch codes

Postby Hando Penu » Wed Apr 25, 2012 6:09 am

Hi!

Try to adjust gamma little bit. It may help. Advanced clarity makes wornders, but it will cost a lot in performance :(
And check the scanner - so it is properly calibrated and produces clean uniform images in grayscale/color.

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