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displaying 16-bit TIFF

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Chuan Zeng

displaying 16-bit TIFF

Hi, folks,

Does anyone know what happens when I open a 16-bit TIFF file? I guess
the intensity should have been converted to 8-bit so that it can be
displayed on monitor. I can tell that the conversion is definitely NOT
like *255/65535. Maybe the conversion was taken according to some tags
hidden in the file? Any tip is appreciated. Thanks!

Chuan

Vergara, Leoncio A.

Re: displaying 16-bit TIFF

how was the image acquired? did u use a 12 bit device?

________________________________________
From: ImageJ Interest Group [[hidden email]] On Behalf Of Chuan Zeng [[hidden email]]
Sent: Friday, October 24, 2008 6:34 PM
To: [hidden email]
Subject: displaying 16-bit TIFF

Hi, folks,

Does anyone know what happens when I open a 16-bit TIFF file? I guess
the intensity should have been converted to 8-bit so that it can be
displayed on monitor. I can tell that the conversion is definitely NOT
like *255/65535. Maybe the conversion was taken according to some tags
hidden in the file? Any tip is appreciated. Thanks!

Chuan

Jim Passmore

Re: displaying 16-bit TIFF

In reply to this post by Chuan Zeng

Chuan

Off the top of my head, I think it maps the darkest pixel to 0 and the
brightest to 255, with a linear ramp between the extremes.

from http://rsb.info.nih.gov/ij/docs/concepts.html

16-bit and 32-bit grayscale images are not directly displayable on computer
monitors, which typically can show only 256 shades of gray. Therefore, the
data are mapped to 8-bits by windowing. The window defines the range of
gray values that are displayed: values below the window are made black,
while values above the window are white. The window is defined by minimum
and maximum values that can be modified using
Image/Adjust/Brightness/Contrast.

Jim

----------------------------------------------
Jim Passmore
Research Associate
Sealed Air Corporation
[hidden email]
864-433-2927 voice
864-433-2205 fax
----------------------------------------------

ImageJ Interest Group <[hidden email]> wrote on 10/24/2008 07:34:39
PM:

> Hi, folks,
>
> Does anyone know what happens when I open a 16-bit TIFF file? I guess
> the intensity should have been converted to 8-bit so that it can be
> displayed on monitor. I can tell that the conversion is definitely NOT
> like *255/65535. Maybe the conversion was taken according to some tags
> hidden in the file? Any tip is appreciated. Thanks!
>
> Chuan

Joachim Wesner

Antwort: Re: displaying 16-bit TIFF

Hi,

yes, by default it´s the way you describe, but you can verify and change
the mapping anytime using Image/Adjust/Brithtness/Contrast resp.
Ctl-Shift-C
as described in the concepts document.

Also, don´t really expect a "linear" mapping from 16-Bit values to screen
brightness or whatever, usually any display device has inherent or emulated
"gamma" value of 1.8 to 2.2 built in. (Which on even a pretty good LCD
screen might change tremendously with viewing angle)

Also,

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Wetzlar HRB 2432
Geschäftsführer: Dr. Stefan Traeger | Dr. Wolf-Otto Reuter | Dr. David Roy
Martyr | Colin Davis

Jim Passmore
<James.Passmore@S
EALEDAIR.COM> An
Gesendet von: [hidden email]
ImageJ Interest Kopie
Group
<[hidden email]. Thema
GOV> Re: displaying 16-bit TIFF

27.10.2008 16:22

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

Chuan

Off the top of my head, I think it maps the darkest pixel to 0 and the
brightest to 255, with a linear ramp between the extremes.

from http://rsb.info.nih.gov/ij/docs/concepts.html

16-bit and 32-bit grayscale images are not directly displayable on computer
monitors, which typically can show only 256 shades of gray. Therefore, the
data are mapped to 8-bits by windowing. The window defines the range of
gray values that are displayed: values below the window are made black,
while values above the window are white. The window is defined by minimum
and maximum values that can be modified using
Image/Adjust/Brightness/Contrast.

Jim

----------------------------------------------
Jim Passmore
Research Associate
Sealed Air Corporation
[hidden email]
864-433-2927 voice
864-433-2205 fax
----------------------------------------------

ImageJ Interest Group <[hidden email]> wrote on 10/24/2008 07:34:39
PM:

> Hi, folks,
>
> Does anyone know what happens when I open a 16-bit TIFF file? I guess
> the intensity should have been converted to 8-bit so that it can be
> displayed on monitor. I can tell that the conversion is definitely NOT
> like *255/65535. Maybe the conversion was taken according to some tags
> hidden in the file? Any tip is appreciated. Thanks!
>
> Chuan

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