primax: Thread: primaxd with gamma problem?

It's enclosed with this mail two jpegs. One (test-win.jpg) produced with de 
original program, in windows; the other(test-lin.jpg) with the primaxd0.5 and 
xsane.

The 2 images were scanned with the defaults values of color, contrasts, gamma 
etc. We can see, in the test-lin.jpg, problems in gamma and in the "color 
detection".

Its a problem of primaxd, isn't it? it occurs with you too? 

I tried using the gamma correction, color etc, but I couldn't scan this image 
with primad equal to the win-image.

Note1: My scanner is an colorado 300.
Note2: Its happen with couple of images.

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On Wed, 27 Mar 2002, Louco.com [iso-8859-1] você na internet. wrote:

> I tried using the gamma correction, color etc, but I couldn't scan this image
> with primad equal to the win-image.
>
> Note1: My scanner is an colorado 300.
> Note2: Its happen with couple of images.

My scanner is also a colorado 300.
Same problem.
I wrote Andre about this a while ago, here is the answer he gave:

--------------------------------------------------------

A better solution is to use xscanimage. It has a difficult to use but
mighty histogramm function. Create a line with a very low gamma value.
This worked for me.

[ note:  xscanimage is the interface gimp uses for scanning ]

I send you a snapshot of my setting. The diagram creates a mapping from
the input color values to the output color values. The x axis is the input
color - the more right the more white. The higher the value at a point the
whiter the output color. So a point in the top right corner means: "map a
full white input value to a full white output value". A point in the
bottom left corner says: "Map black input values to black output values".
The points between these are up to you. What you want for your pencil
drawings is: "Map only the really white imput to white output - all others
shall be black". You can get this by selecting a really low gamma value.
This creates a appropriate mapping. The problem: (1) Xsane has a lower
limit - you cannot select really low one. (2) XScanimage has a bug. If you
create the mapping with the gamma button there are negative values in the
mapping. So it inverts the image. I will write a bug report to the
author.
The solution: create the mapping by hand. XScanimage has a cool spline
interpolation function (the topmost button). Create some points and it will
connect them with smooth a line.

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Andre's suggestion works quite well, actually, but when I have to scan
really faded images or really light pencil drawings I still have to switch
over to windows or use the old primax scan program instead of primaxd.

-- 
Michele Alzetta

On Wed, 27 Mar 2002, Louco.com [iso-8859-1] você na internet. wrote:

> It's enclosed with this mail two jpegs. One (test-win.jpg) produced with de
> original program, in windows; the other(test-lin.jpg) with the primaxd0.5 and
> xsane.
>
> The 2 images were scanned with the defaults values of color, contrasts, gamma
> etc. We can see, in the test-lin.jpg, problems in gamma and in the "color
> detection".
>
> Its a problem of primaxd, isn't it? it occurs with you too?
>
> I tried using the gamma correction, color etc, but I couldn't scan this image
> with primad equal to the win-image.
>
> Note1: My scanner is an colorado 300.
> Note2: Its happen with couple of images.
>
> --------------------------------------------------------------------------
>    -o)(o-   Sem noção joselito, sem noção!
>  -./\\//\.- Slackware 8 vs. Cubo Linux Beta 123
>   _\_VV_/_  Por que usar as janelas se você pode usar a Porta?
> --------------------------------------------------------------------------
>
>
>

This should  also become a FAQ :-).

it is indeed a problem of XSAne.
Try the good old xscanimage. Play a little bit around with the gamma
values and make it work.

You could also try to complain with Oliver Rauch( the author of XSane).
It schould include better gamma controls.

Bye

Andre

Okz. Thank you, Andre, and Michele, too.

--------------------------------------------------------------------------
   -o)(o-   Sem noção joselito, sem noção!
 -./\\//\.- Slackware 8 vs. Cubo Linux Beta 123
  _\_VV_/_  Por que usar as janelas se você pode usar a Porta?
--------------------------------------------------------------------------