24 bit images, but I only see 8 bit values when mouse hovers a pixel.

[rrmarino]

Hello.

I am new to the Image Processing world. Therefore please have that in mind when answering this.


If an image is 24 bits per pixel (16581375 colors maximum) , why do I see only up to  255 (max number in 8 bit) in imageJ bar when the mouse hovers a pixel?

thanks

Rodrigo

:)

[Jacqueline Ross]

Hi Rodrigo,

Since you have a colour image (24bit), you therefore only have 256 (range 0-255) grey values in each channel, Red + Green + Blue. Each channel image is 8bit.

So when you hover, you should see 3 numbers, e.g. 0, 117, 217. These are the 3 grey values in order, R, G, B.

Kind regards,

Jacqui

Jacqueline Ross

Biomedical Imaging Microscopist
Biomedical Imaging Research Unit
School of Medical Sciences
Faculty of Medical & Health Sciences
The University of Auckland
Private Bag 92019
Auckland, NEW ZEALAND

Tel: [phone] Ext 87438
Fax: [phone]

http://www.fmhs.auckland.ac.nz/sms/biru/


-----Original Message-----
From: ImageJ Interest Group [mailto:[hidden email]] On Behalf Of rrmarino
Sent: Friday, 30 September 2011 6:13 p.m.
To: [hidden email]
Subject: 24 bit images, but I only see 8 bit values when mouse hovers a pixel.

Hello.

I am new to the Image Processing world. Therefore please have that in mind
when answering this.


If an image is 24 bits per pixel (16581375 colors maximum) , why do I see
only up to  255 (max number in 8 bit) in imageJ bar when the mouse hovers a
pixel?

thanks

Rodrigo

:)





--
View this message in context: http://imagej.588099.n2.nabble.com/24-bit-images-but-I-only-see-8-bit-values-when-mouse-hovers-a-pixel-tp6846509p6846509.html
Sent from the ImageJ mailing list archive at Nabble.com.

[Michael Boyle]

Sounds like you have an 8 bit color rgb camera.  This is referred to as 24 bit image because  8 bits x 3 channels (red, green, blue) = 24 bit at each pixel location.  However each pixel location does not display a range of 16581375 color values as you mention for r,g,b.  R,g,b data for each pixel are 255 per channel.  255 to third power gives you 16581375 different unique combinations of r,g,b values possible at each pixel location which is referred to as 24 bits per pixel.

Michael Boyle  
------Original Message------
From: rrmarino
Sender: ImageJ Interest Group
To: [hidden email]
ReplyTo: ImageJ Interest Group
Subject: 24 bit images, but I only see 8 bit values when mouse hovers a pixel.
Sent: Sep 30, 2011 1:12 AM

Hello.

I am new to the Image Processing world. Therefore please have that in mind
when answering this.


If an image is 24 bits per pixel (16581375 colors maximum) , why do I see
only up to  255 (max number in 8 bit) in imageJ bar when the mouse hovers a
pixel?

thanks

Rodrigo

:)





--
View this message in context: http://imagej.588099.n2.nabble.com/24-bit-images-but-I-only-see-8-bit-values-when-mouse-hovers-a-pixel-tp6846509p6846509.html
Sent from the ImageJ mailing list archive at Nabble.com.

Sent from my Verizon Wireless BlackBerry

[rrmarino]

Michael and Jacqui , thank you very much! Clear and concise explanation.

Rodrigo :)

[John Kielkopf]

Perhaps your image is 8 bits per color, three colors, so 24 bits total.

On Fri, Sep 30, 2011 at 1:12 AM, rrmarino <[hidden email]> wrote:

> Hello.
>
> I am new to the Image Processing world. Therefore please have that in mind
> when answering this.
>
>
> If an image is 24 bits per pixel (16581375 colors maximum) , why do I see
> only up to  255 (max number in 8 bit) in imageJ bar when the mouse hovers a
> pixel?
>
> thanks
>
> Rodrigo
>
> :)
>
>
>
>
>
> --
> View this message in context: http://imagej.588099.n2.nabble.com/24-bit-images-but-I-only-see-8-bit-values-when-mouse-hovers-a-pixel-tp6846509p6846509.html
> Sent from the ImageJ mailing list archive at Nabble.com.
>

--
John Kielkopf
Professor of Physics and Astronomy
University of Louisville
Louisville, KY 40292
Tel:[phone]
Fax:[phone]