Re: wand

Posted by Michael Schmid on Dec 21, 2009; 7:00pm
URL: http://imagej.273.s1.nabble.com/wand-tp3689962p3689965.html

Hi Bill,

it seems that the description of the wand tool options is missing in  
the documentation.

Tolerance: The Wand takes the pixel value where you click as an  
initial value. It then selects a contiguous area under the condition  
that all pixel values in that area must be in the range initial_value  
- tolerance to initial value + tolerance.

4-connected: Only the four neighbors of a pixel are considered  
neighbors. E.g., the wand does not follow a one-pixel wide diagonal  
line because the pixels of that line are not four-connected.

8-connected: Each pixel is considered to have 8 neighbors. So the  
wand follows a diagonal line if you click onto it. On the other hand,  
if you have an area of constant value dissected by a one-pixel wide  
diagonal line, the 8-connected wand will "jump over the line" and  
include the other part of that area.

The wand has no fixed width; the selected area depends on the image  
data. If you want to select an area of 5 pixels width use the  
selection brush. You find it by right-clicking into the Oval tool;  
double click for setting the width.

The selection brush is not macro-recordable. If you want to save a  
selection created by the brush, use the ROI manager; restoring a  
selection from the ROI manager can be done in a macro.

Michael
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On 21 Dec 2009, at 17:19, Rothman, William wrote:

> Michael,
> Thanks for you quick response.
> But what is tolerance and does 4-connected mean 4 pixel wide wand??
> Bill R.