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Multiply by factor

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Jo C. Bruusgaard-2

Multiply by factor

Hi,

The camera I am using has got a spatial nonlinearity, and i need to
reduce dark pixels less than light pixels, so a regular subtraction
won't do. I wondered whether it is possible in ImageJ to multiply
each pixel by a factor set by the user.

Dr. Jo C. Bruusgaard
Department of Molecular Biosciences
University of Oslo
PO Box 1041, Blindern
N-0316 Oslo
NORWAY
Phone: +4722854074
Fax: +4722854664
Mobile: +4790550997

Joachim Wesner

Antwort: Multiply by factor

Hi Jo,

easy, use Process/Math!

However, IMHO, only a factor is no NONLINEARITY, you might talk about a
special power function or similar?

You can also use "Macro" to define a formula, however, AFAIK, nothink that
resembles an "if"-construct

Mit freundlichen Grüßen / Best regards

Joachim Wesner

Leica Microsystems CMS GmbH | GmbH mit Sitz in Wetzlar | Amtsgericht
Wetzlar HRB 2432
Geschäftsführer: Dr. Stefan Traeger | Dr. Wolf-Otto Reuter | Dr. David Roy
Martyr | Colin Davis
www.leica-microsystems.com

"Jo C.
Bruusgaard"
<bruusgaard@GMAIL An
.COM> [hidden email]
Gesendet von: Kopie
ImageJ Interest
Group Thema
<[hidden email]. Multiply by factor
GOV>

28.10.2009 10:43

Bitte antworten
an
ImageJ Interest
Group
<[hidden email].
GOV>

Hi,

The camera I am using has got a spatial nonlinearity, and i need to
reduce dark pixels less than light pixels, so a regular subtraction
won't do. I wondered whether it is possible in ImageJ to multiply
each pixel by a factor set by the user.

Dr. Jo C. Bruusgaard
Department of Molecular Biosciences
University of Oslo
PO Box 1041, Blindern
N-0316 Oslo
NORWAY
Phone: +4722854074
Fax: +4722854664
Mobile: +4790550997

______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email
______________________________________________________________________

Jo C. Bruusgaard-2

Re: Antwort: Multiply by factor

Joachim,

Thanks for a swift answer, and it did help me a lot! (in terms of
what ImageJ can do)

My problem is that it is nonlinear with respect to "spatiality" i.e.
the pixels in top of the chip is more sensitive than the ones at the
bottom. So when I test for camera linearity, the pixels on top of the
image (chip) are linear (Input vs output) but the pixels at the
bottom of the image does not follow the same slope. Any idea on how I
can compensate for this?

On Oct 28, 2009, at 11:02 AM, Joachim Wesner wrote:

> Hi Jo,
>
> easy, use Process/Math!
>
> However, IMHO, only a factor is no NONLINEARITY, you might talk
> about a
> special power function or similar?
>
> You can also use "Macro" to define a formula, however, AFAIK,
> nothink that
> resembles an "if"-construct
>
> Mit freundlichen Grüßen / Best regards
>
> Joachim Wesner
>
> Leica Microsystems CMS GmbH | GmbH mit Sitz in Wetzlar | Amtsgericht
> Wetzlar HRB 2432
> Geschäftsführer: Dr. Stefan Traeger | Dr. Wolf-Otto Reuter | Dr.
> David Roy
> Martyr | Colin Davis
> www.leica-microsystems.com
>
>
>
>
> "Jo C.
> Bruusgaard"
>
> <bruusgaard@GMAIL An
> .COM> [hidden email]
> Gesendet
> von: Kopie
> ImageJ Interest
>
> Group Thema
> <[hidden email]. Multiply by factor
> GOV>
>
>
> 28.10.2009 10:43
>
>
> Bitte antworten
> an
> ImageJ Interest
> Group
> <[hidden email].
> GOV>
>
>
>
>
>
>
> Hi,
>
> The camera I am using has got a spatial nonlinearity, and i need to
> reduce dark pixels less than light pixels, so a regular subtraction
> won't do. I wondered whether it is possible in ImageJ to multiply
> each pixel by a factor set by the user.
>
>
> Dr. Jo C. Bruusgaard
> Department of Molecular Biosciences
> University of Oslo
> PO Box 1041, Blindern
> N-0316 Oslo
> NORWAY
> Phone: +4722854074
> Fax: +4722854664
> Mobile: +4790550997
>
>
>
> ______________________________________________________________________
> This email has been scanned by the MessageLabs Email Security System.
> For more information please visit http://www.messagelabs.com/email
> ______________________________________________________________________

Jo C. Bruusgaard
[hidden email]

Joachim Wesner

Antwort: Re: Antwort: Multiply by factor

Hi again,

you mean you have a spatially varying sensitivity?

This could be fixed with a bit of macro or a plugin that loops through all
the pixels, HOWEVER, IF

you can generate an image with the same size as your images (width/height
in pixels), where each
pixels represenst the local sensitivity, (take the image of an evenly
illuminated area!?), you can simply
use Process/Image Calculator with "Divide" to normalize your camera image!

Joachim Wesner

"Jo C.
Bruusgaard"
<bruusgaard@GMAIL An
.COM> [hidden email]
Gesendet von: Kopie
ImageJ Interest
Group Thema
<[hidden email]. Re: Antwort: Multiply by factor
GOV>

28.10.2009 15:43

Bitte antworten
an
ImageJ Interest
Group
<[hidden email].
GOV>

Joachim,

Thanks for a swift answer, and it did help me a lot! (in terms of
what ImageJ can do)

My problem is that it is nonlinear with respect to "spatiality" i.e.
the pixels in top of the chip is more sensitive than the ones at the
bottom. So when I test for camera linearity, the pixels on top of the
image (chip) are linear (Input vs output) but the pixels at the
bottom of the image does not follow the same slope. Any idea on how I
can compensate for this?

On Oct 28, 2009, at 11:02 AM, Joachim Wesner wrote:

Jo C. Bruusgaard
[hidden email]

______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email
______________________________________________________________________