Reducing background noise in images

[Mike]

Can anyone offer advice on techniques to reduce background noise in scanned
images of text? I print a page of faded or blotchy handwritten text from a
microfilm reader. I then scan the printout and try to enhance the image to
make the handwriting more readable. I've tried several graphics programs
and different enhancement techniques without success: Edge detect, reduce
noise, convert to gray scale, negative, contrast, etc. The best I've found
so far is logarithmic lut, which makes the background noise more uniform,
but still doesn't bring out the fainter lines on the letters. Can anyone
recommend image enhancements that have worked for them?

Thanks,
Mike

[K0BBE]

"Mike" <[email protected]> schreef ...

Can anyone offer advice on techniques to reduce background noise
in scanned
images of text? I print a page of faded or blotchy handwritten
text from a
microfilm reader. I then scan the printout and try to enhance
the image to
make the handwriting more readable. I've tried several graphics
programs
and different enhancement techniques without success: Edge
detect, reduce
noise, convert to gray scale, negative, contrast, etc. The best
I've found
so far is logarithmic lut, which makes the background noise more
uniform,
but still doesn't bring out the fainter lines on the letters.
Can anyone
recommend image enhancements that have worked for them?

Thanks,
Mike

Don't make your scan in .JPEG-format, but in TIFF.
The difference is like heaven and earth !

--
K0BBE [ http://go.to/coilge ]
e-adres: incorrect

[Dave Hinz]

On Fri, 22 Apr 2005 15:16:11 -0500, Mike <[email protected]> wrote:

Can anyone offer advice on techniques to reduce background noise in scanned
images of text?

One technique I've used is to scan 8-bit greyscale, and then play with
"threshhold" to tell it which is black, and which is white - throwing out
all grey. Hopefully the noise is grey.

If that doesn't work, Photoshop has a good "despeckle" filter.

I print a page of faded or blotchy handwritten text from a
microfilm reader. I then scan the printout and try to enhance the image to
make the handwriting more readable. I've tried several graphics programs
and different enhancement techniques without success: Edge detect, reduce
noise, convert to gray scale, negative, contrast, etc. The best I've found
so far is logarithmic lut, which makes the background noise more uniform,
but still doesn't bring out the fainter lines on the letters. Can anyone
recommend image enhancements that have worked for them?

Ah, is this written or typed text?

[Denis Beauregard]

On Fri, 22 Apr 2005 15:16:11 -0500, "Mike" <[email protected]> wrote
in soc.genealogy.computing:

Can anyone offer advice on techniques to reduce background noise in scanned
images of text? I print a page of faded or blotchy handwritten text from a
microfilm reader. I then scan the printout and try to enhance the image to
make the handwriting more readable. I've tried several graphics programs
and different enhancement techniques without success: Edge detect, reduce
noise, convert to gray scale, negative, contrast, etc. The best I've found
so far is logarithmic lut, which makes the background noise more uniform,
but still doesn't bring out the fainter lines on the letters. Can anyone
recommend image enhancements that have worked for them?

When you print a page, you print it in black and white with no
grey scale at all.

So, you must find some filter in your paint program that will
first change the scanned page into something with grey scale.
No idea which effect will do it.


Denis

[Stephen SG]

This may be the program to help you.

Regards Stephen SG

http://www.irfanview.com/index.htm



"Mike" <[email protected]> wrote in message
news:[email protected]...
| Can anyone offer advice on techniques to reduce background noise in
scanned
| images of text? I print a page of faded or blotchy handwritten text from
a
| microfilm reader. I then scan the printout and try to enhance the image
to
| make the handwriting more readable. I've tried several graphics programs
| and different enhancement techniques without success: Edge detect, reduce
| noise, convert to gray scale, negative, contrast, etc. The best I've
found
| so far is logarithmic lut, which makes the background noise more uniform,
| but still doesn't bring out the fainter lines on the letters. Can anyone
| recommend image enhancements that have worked for them?
|
| Thanks,
| Mike
|
|

[singhals]

Mike wrote:

Can anyone offer advice on techniques to reduce background noise in scanned
images of text? I print a page of faded or blotchy handwritten text from a
microfilm reader. I then scan the printout and try to enhance the image to
make the handwriting more readable. I've tried several graphics programs
and different enhancement techniques without success: Edge detect, reduce
noise, convert to gray scale, negative, contrast, etc. The best I've found
so far is logarithmic lut, which makes the background noise more uniform,
but still doesn't bring out the fainter lines on the letters. Can anyone
recommend image enhancements that have worked for them?

I've had some luck, in the past, using colors. Working with a
full-color scan, AND A COPY OF IT!, I've made the black/grey letters I
care about green in the copy. It is often very easy to see the missing
parts of an s or a t or an m when the surrounding area is green and the
rest isn't. I tend to use good ol' PAINT for this, more from habit than
conviction. It uses a fair amount of time, but it's surprising what can
be done.

Cheryl

[Dennis Lee Bieber]

On Fri, 22 Apr 2005 15:16:11 -0500, "Mike" <[email protected]>
declaimed the following in soc.genealogy.computing:

and different enhancement techniques without success: Edge detect, reduce

I'd think noise would be emphasized by "edge detect".

noise, convert to gray scale, negative, contrast, etc. The best I've found

I pretty much never play with contrast (or brightness)
modifications.

If you consider a function of input->output, no modification
gives you a diagonal line. (view this in fixed pitch)


/ 255 out
/
/
/ 0
0 255
in

Contrast works by rotating that line, and brightness moves it up
and down. Problem, for much work, is that you run out of range rapidly,
and map many shades to the same limit.

Gamma adjustments often work better, as they leave the
end-points alone (0=>0, 255=>255), while changing from a diagonal to a
smooth curve. Reducing the gamma will make the output "trail" the input
-- overall, the darks become darker, and then the lighter shades become
lighter much faster. Raising gamma will make the darks become lighter,
while slowing the change in the lighter area..

Photoshop even has a "curves" tool, where you can draw the
conversion as a custom curve -- you could have middle range stuff
actually output in negative while the darks and brights stay positive.
This may bring out perceptually some details.

--

==============================================================
[email protected] | Wulfraed Dennis Lee Bieber KD6MOG
[email protected] | Bestiaria Support Staff
==============================================================
Home Page: <http://www.dm.net/~wulfraed/
Overflow Page: <http://wlfraed.home.netcom.com/

[JazerNorth]

Try GIMP http://www.gimp.org/. It has many photo scripts that might do
what you want. If you don't find one in the base package, there are
many add ons that might. I have modified many images and removed noise
(though not for text) from them.

JazerNorth

[Mike]