good tool to convert scanned documents from 24/8 bit to 1-bit ???

[spoon2001]

I've been scanning old documents with a sheet-fed scanner - different page
sizes, different image characteristics, etc.

Rather than scanning directly to correctly cropped 1-bit images, I thought I
would just batch scan everything, and do my cropping, deskewing, and color
depth reduction later. Particularly for scanning to 1-bit color depth,
different threshold values are better for different documents.

I need a tool that would allow me to quickly browse through a bunch of 24/8
bit document images. For each document I need a slider to adjust the
threshold level to the best results (with a preview of what the results will
be). Then I want to reduce color depth to 1-bit using the selected
threshold, and save the image to a 1-bit Group 4 TIF file.

I've tried all the programs I have available - Paperport, Irfanview, Xnview,
GIMP, Paint Shop Pro, and none of these programs does what I'm looking for,
at least not adequately or conveniently.

I've tried the batch conversion features of Irfanview, Xnview, and PSP, and
none of them are satisfactory. I haven't even figured out how to set any
threshold value for the color depth reduction before doing the batch
conversion. And even that wouldn't be what I'm looking for - because
different documents need different threshold values in doing the conversion
to 1-bit.

 

[Andreas Hirczy]

I need a tool that would allow me to quickly browse through a bunch of 24/8
bit document images. For each document I need a slider to adjust the
threshold level to the best results (with a preview of what the results
will be). Then I want to reduce color depth to 1-bit using the selected
threshold, and save the image to a 1-bit Group 4 TIF file.

For the color reduction I'd try mkbitmap:
<http://potrace.sourceforge.net/mkbitmap.html>

Andreas

 

[Wayne Fulton]

I need a tool that would allow me to quickly browse through a bunch of 24/8
bit document images. For each document I need a slider to adjust the
threshold level to the best results (with a preview of what the results will
be). Then I want to reduce color depth to 1-bit using the selected
threshold, and save the image to a 1-bit Group 4 TIF file.

I'd just scan them in line art mode myself, using the scanners threshold
adjustment. One setting normally works well for similar documents.

Paintshop Pro has the menu Color - Adjust - Threshold which does it with
a small preview. This step also reduces image to 1 bit line art, that's what
Threshold does. Then its TIF format supports G3 compression (not G4). G4
is not found often in photo programs.

Adobe Elements is very similar, menu Image - Mode - Bitmap - Threshold
(but the image must be grayscale first).