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Author Topic: image problem  (Read 1812 times)

kalos

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image problem
« on: September 28, 2008, 05:22:07 AM »
hello

I scan at TIF 600dpi greyscale in my scanner

as you can see in this screenshot, the scanner somehow produces images with some marks around the characters, I don't know if glossy paper is responsible for this (the marks look like reflections) or the scanner or something else

this is the crop of a scanned page:
http://img525.imageshack.us/img525/8014/33734607td2.png
image problem


this is the same crop but with lowered brightness and contrast in photoshop that makes those marks much more visible:
http://img297.imageshack.us/img297/2667/11316679dt4.png
image problem


the marks around the characters cause problems to the OCR program and this reports some characters as 'uncertain characters' or recognizes them erroneously

do you know what causes this and if there is a way to fix it

thanks

Carol Haynes

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Re: image problem
« Reply #1 on: September 28, 2008, 06:13:16 AM »
Why not scan in B&W and if the OCR program needs to use greyscale convert the image to greyscale.

Failing that tell use what kind of scanner you use. If you can alter brightness and contrast does increasing contrast and lowering brightness help?

Also check the instructions for your OCR app - 600dpi scanning should not be necessary for OCR.

kalos

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Re: image problem
« Reply #2 on: September 28, 2008, 06:28:02 AM »
I will test this (BW and then greyscale conversion)

my scanner is opticbook 3600 and it has contrast, brightness, gamma correction adjustments, but the preview area is small to distinguish any detail and it's hard to find the optimum combination of those three values

Carol Haynes

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Re: image problem
« Reply #3 on: September 28, 2008, 06:39:48 AM »
Does your OCR have a scanner optimization wizard - many do.

If your scanner is not easy to adjust and giving poor quality output can you afford to change it? Many of the Canon Scanners are pretty cheap and give very good quality scans with easy to use software with up to full screen previews and a zoom feature to check regions of an image and accurately select the region you want to scan. I have a CanoScan 3200F which is pretty long in the tooth now but it still works brilliantly. The 3200F will even scan photo negatives and slides and does a reasonable job of that.