Posted by
lechristophe on
Oct 24, 2006; 9:58am
URL: http://imagej.273.s1.nabble.com/can-i-draw-cylinders-tp3701211p3701213.html
I think he may refer to a line with a finite width : adjust the line
width by double clicking the line tool.
As regards segmented or freehand lines with a fixed width, it is not yet
implemented. I desperately need it to do measurements on thick neurites
and I've spent hours trying to figure out how to write such a tool with
a macro. The only output of my efforts so far have been massive headache...
What I understood was that line objects (such as segmented or freehand
lines) are very different from surface objects (rectangles etc...),
because they are not measured in the same way (length vs area). So
having a straight line with a finite width is relatively straighforward,
because length and area are linked very simply, but for segmented lines
with a finite width (which i call "kinky snakes"), or even worst for
freehand "snakes", the relationship is much more complicated.
What would be needed is a way to draw a line (wathever the type) and
having some kind of "expand" command to generate a thick snake from that
line, that would then be considered as a surface ROI, not a linear one.
Alternatively, one could think about manually generate a rectangle from
the extremities of a straight line, and process segmented lines by
iteration (segment by segment). For that, I need a way to specifiy a
rectangular ROI (not horizontal or vertical, but with any inclination)
from the segment extremities. These extremities corresponds to the
middle points of the two opposite (parallel) sides of the rectangle.
Using these points and and the lenght of the corresponding side defines
a unique rectangle, but there is no way to define a rectangular ROI
using this parameters in ImageJ.
Knowing the straight lins coordinates and the width of the rectangle, it
could be done by calculating the rectangle four corners coordinates, but
I somehow got lost in the calculus somewhere among angles, arctan and
triangle sides ratios...
Jeez this is where posting a drawing could help explain what I'm saying.
If someone is able to figure out a quick hack to be able to draw a
segmented line, expand it to a "kinky snake" and process that as a
surface ROI (not a linear one), all of this wrapped into a easy-to-use
single tool, it would be christmas in advance.
Christophe
--
Christophe Leterrier
Postdoc
INSERM UMR641 Neurobiology of ionic channels
IFR Jean Roche - Mediterranee University
Marseille, France
Robert Baer wrote:
> I want to know if I can draw cylindrical lines in 2D in imageJ
> - A cylinder is a 3-dimensional object, not a 2D object
> - A line is a 1-dimensional object (although sometimes given width for
> visualization purposes), not a 2D object.
> - What, therefore, do you mean by a cylindrical line on a 2D image?
> And, do you mean a stack of 2D images?
>
> Help us if you want us to help you.
>
>
> ----- Original Message ----- From: "sridevi polavaram" <
[hidden email]>
> To: <
[hidden email]>
> Sent: Monday, October 23, 2006 12:40 PM
> Subject: can i draw cylinders!
>
>
>> Dear ImageJ,
>> I want to know if I can draw cylindrical lines in 2D in imageJ. I don't
>> see any such tool avaiable on the main window. But is there any
>> plugin that
>> provides this facility?
>> If not, what is the solution!? I hope atleast one of you might have
>> needed
>> this! please let me know.
>> -Thanks
>> Sri
>>
>