[sane-devel] help with improving text scans

[m. allan noah]

On Fri, Dec 19, 2008 at 12:58 PM, gobo <gobo770 at gmail.com> wrote:
> the default for scanimage is 75dpi, and that is barely readable.  i'll
> certainly give your gimp setting change a try.
>
> but, can i also do this in the shell?  can i take an image scanned
> with --resolution=150, funnel it through another utility (or two) and
> end up  with a pdf containing 8.5x11" hi-res pages?

you are confusing the dpi of the scan and the dpi of the print. If you
scan at 150, you should print at 150, if you want the size to match.
Since the scans as the come from sane likely wont have the dpi
embedded, you will have to tell someone in your chain of progs what
the original scan dpi was. try the -density flag to convert.

allan

>
> what i do now when i need a print from a scanned image:
>   convert filename.pgm filename.ps
>   ps2pdf filename.ps
>
> with anything larger than 75dpi, the pdf is junk.  i can add the
> -resize option to convert, and that helps, but not much.  the document
> is still hard to read.
>
>
>
> On Fri, Dec 19, 2008 at 10:51 AM, m. allan noah <kitno455 at gmail.com> wrote:
>> The gimp probably defaults images to something like 72dpi. if you have
>> scanned at a higher dpi, it wont know, and will print it huge. just
>> change the print dpi in the gimp to match that at which you scanned.
>> look in the image->print size menu option
>>
>> allan
>>
>> On Fri, Dec 19, 2008 at 11:34 AM, gobo <gobo770 at gmail.com> wrote:
>>> for some time now i've been using homemade scripts with scanimage and
>>> scanadf to scan my paper documents. most of my documents are plain
>>> text. the results have always been poor and marginally acceptable. i'm
>>> using suse 10.3 and an hp aio j6450 or psc1210xi.
>>>
>>> recently i obtained a canon scanner w/adf for use at work where i must
>>> use windows. to get around the image compatibility issues of microsoft
>>> document imaging (office 2003) i simply print the scanned image to pdf
>>> with acrobat. the results obtained with mdi are far superior to
>>> anything i've ever been able to achieve with sane apps.
>>>
>>> i've spent hours fumbling around with scanimage options, imagemagick
>>> convert to resize the images and ps2pdf to produce the pdf files.
>>> while i have made some slight improvements over the default settings,
>>> i've never been able to get even close to the mdi output. in the few
>>> places where i must have a good scan, i use resolutions of 150 or 300,
>>> but to get prints of the image becomes a real pain. i must load the
>>> image in gimp, fiddle around resizing it and then printing.
>>>
>>>
>>> my standard scanimage script would contain:
>>> scanimage -x 215.9 -y 297 -d
>>> hpaio:/net/Officejet_J6400_series?ip=192.168.1.103 \
>>> -pv --mode gray > $FILE
>>>
>>>
>>> pieces from a perl script using the adf:
>>> # this is the scan device
>>> @scanr = ("hpaio:/net/Officejet_J6400_series?ip=192.168.1.103");
>>> # these are the command line options for scanadf
>>> @opts = ("-x 215.9 -y 297 -v --mode=gray --source ADF --batch-scan=no -e 1");
>>>
>>> # scan page
>>> system("scanadf @opts -d @scanr -o $fnamepg");
>>>
>>> adding --resolution=150, or 300 does produce a larger image, with less
>>> artifacting, and much more readable, but difficult to print.
>>>
>>> the answer must be one of two things -- either i'm missing something
>>> real simple about producing hi-res 8.5x11" images (that is right in
>>> front of my nose) or we are just not there yet with linux scanning.
>>>
>>> can someone correct, or put me on a better path?
>>>
>>> thanks.
>>>
>>> --
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>>>
>>
>>
>>
>> --
>> "The truth is an offense, but not a sin"
>>
>



-- 
"The truth is an offense, but not a sin"