Re: Standard set of image pre-processing filters for poorly hand printed images?

On Nov 12, 8:07 am, Raj <kr_...@xxxxxxxxx> wrote:
On 5 Nov, 21:38, Milind Joshi <milind.a.jo...@xxxxxxxxx> wrote:



Hi,

Does anyone know of a standard filter or filters applied in sequence
to a B/W hand printed images to fill in broken lines, etc., without
affecting those characters that are well-written with complete
strokes?

We have a bunch of images with different writing styles, applying a
single set of filters on all of them deteriorates quality on those
images that were good.

Also, applying filters and checking results to see if the filter was
OK is too time-consuming.

Standard thickening/smoothing operations built into OCR/ICR engines
didn't work very well, so we're going to have to write a custom image
pre-processor for these images.

You can find a sample athttp://www.ideatechnosoft.com/sci.image.processing/2007_11_05_sci.ima...

There are many more samples, so that should not be a problem if you
want us to try out suggestions on a wider set of images.

What would be a general approach to arrive at a good sequence of image
processing filters or to choose the best one for the job? Is there a
filter out there that is recommended for this type of problem?

Any help, pointers, reading material, manuals, expert suggestions
would be greatly appreciated!

Best Regards,
Milind

Hi Milind
Indeed its a difficult problem. the variability of ink density is
proportional to the stroke formation/thickness.
I have few questions to gain a better understanding of your problem
What is the nature of the background of the documents?
Do you have the possibility to handle gray scale images?
Thanks
Raj

Thank you Raj, I appreciate your reply.

The background is actually a red layout that is dropped out by the
scanner.
We cannot use gray scale images because of the limitations of the
client hardware and image volume / disk space concerns.
Even asking them to go up from 200 DPI to 300 DPI took a lot of
convincing.

As I mentioned before, we're trying out erosion/dilation.
We're also trying to look at some form of "growing" in a calculated
direction, but don't have success yet.

Will keep you updated on progress.

Best Regards,
Milind

.

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