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Message-ID:  <[log in to unmask]>
Date:         Sun, 30 Dec 2007 20:39:46 +0100
Reply-To:     ImageJ Interest Group <[log in to unmask]>
Sender:       ImageJ Interest Group <[log in to unmask]>
From:         Michael Schmid <[log in to unmask]>
Subject:      Re: software binning

Hi Joel,

as the name says, the Averaging Reducer calculates an average over
n by n pixels.

Image>Adjust Size: Without "interpolate" it takes the pixel nearest
to the position corresponding to the new pixel center.
With "interpolate", it uses linear interpolation between the nearest
pixels of the original image.

Thus, when downscaling by a factor of 5, the Averaging Reducer will
always take the average of 5x5 = 25 pixels as a new pixel.
Image>Adjust Size will never use more than 4 pixels (those closest
to the position that the output pixel should correspond to).

Adjust Size is better in preserving edges, but it can lead to
aliasing (e.g. missing thin lines) and it does not significantly
reduce the noise.

In theory, the "ideal" downscaling algorithm would be applying a
bandwith-limiting filter first (some sort of sin(x)/x multiplied
by a window function to avoid infinite ringing) and then downsampling
with proper interpolation. But I don't think that anyone has
implemented this so far.
(There is also a downscaling algorithm in GaussianBlur for large
blur radii: This one is bandwidth-limited, but it attenuates high
spatial frequencies more than one would like for downscaling an
image without blurring it).

Michael
__________________________________________________________________

On Sun, 30 Dec 2007 13:46:21 -0500 "Joel Sheffield" <[log in to unmask]>
wrote:
>Michael,
>
>I have been enjoying your comments for some time.  This latest 
>suggestion brings up a question.  What is the difference between the 
>averaging reducer plugin and the scale function that it built into 
>ImageJ?  The difference as shown on the web site for the plugin is 
>very dramatic.
>
>Thanks, and Happy New Year.
>
>Joel
>
>Date sent:      	Sun, 30 Dec 2007 11:24:16 +0100
>Send reply to:  	ImageJ Interest Group <[log in to unmask]>
>From:           	Michael Schmid <[log in to unmask]>
>Subject:        	Re: software binning
>To:             	[log in to unmask]
>
>> Hi Richard,
>> 
>> you need two steps:
>> (1) multiply the image by a factor of your choice, e.g. 4.
>> (2) use the Averaging Reducer plugin (on the ImageJ web site)
>> to reduce the image size by, e.g. a factor of 2 in each direction.
>> 
>> With the multiplication factor of 4, this will be equivalent to
>> 2x2 binning.
>> 
>> To automate it, do it manually and let the Macro Recorder (Plugins>
>> Macros>Record) create a macro for you.
>> 
>> Michael
>> ______________________________________________________________________
>> On Wed, 26 Dec 2007 07:16:30 -0500 Richard Cole <[log in to unmask]>
>> wrote:
>> >Dear Group
>> >
>> >Is there a way to software bin an image?  I have a large format CCD camera
>> >that I would like to software bin to increase brightness.
>> >
>> >Thanks
>> >
>> >RWC
>> >
>> >Richard Cole
>> >Research Scientist IV
>> >Director: Advanced Light Microscopy & Image Analysis Core
>> >Wadsworth Center
>> >P.O. Box 509 Albany N.Y. 12201-0509
>> >* 518-474-7048 
>> >** 518-474-4430  
>> >* [log in to unmask]
>> >Website www.wadsworth.org/cores/alm/index.htm
>> >
>> >IMPORTANT NOTICE: This e-mail and any attachments may contain
>> >confidential or sensitive information which is, or may be, legally
>> >privileged or otherwise protected by law from further disclosure.  It
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>> >
>
>Joel B. Sheffield, Ph.D
>Department of Biology
>Temple University
>Philadelphia, PA 19122
>Voice: 215 204 8839
>e-mail: [log in to unmask]
>URL:  http://astro.temple.edu/~jbs
>

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