Re: Antwort: Re: how to access the ROI programmatically?

Posted by Per Christian Henden on Jul 04, 2006; 7:47am
URL: http://imagej.273.s1.nabble.com/how-to-access-the-ROI-programmatically-tp3702303p3702306.html

Thanks!

Using contains() to build the mask and then just reading the mask to decide if
I want to include the current pixel or not in the computation sounds like a
good idea. To speed things up further I will ignore pixels outside the
bounding rectangle of the ROI completely, i.e. make the for all pixels loop
consider only the bounding rectangle.

Cheers,
PER

On Monday 03 July 2006 22:56, Joachim Wesner wrote:

> Yes, there is contains(), and it´s in the docs
>
> http://rsb.info.nih.gov/ij/developer/api/ij/gui/Roi.html (look for
> contains)
>
> but it´s very general yet a bit slow, in case you need to access it in a
> tight loop you better create that mask Gabriel mentions once like
>
>             byte rMask[] = null;
>             Rectangle rRect = null;
>             if (roi != null) {
>                   rRect = roi.getBounds();
>                   ImageProcessor ipm = roi.getMask();
>                   if (ipm != null) {
>                         rMask = (byte[])ipm.getPixels();
>                   }
>             }
>
> and later use your own contains() function.
>
>       boolean contains(int ix, int iy, byte[] mask, Rectangle rect) {
>
>             if (rect == null)
>                   return true;
>
>             if (!rect.contains(ix, iy))
>                   return false;
>
>             if (mask == null)
>                   return true;
>
>             return (mask[(iy-rect.y)*rect.width+(ix-rect.x)] != 0);
>       }
>
> in a tight loop like
>
> if (contains(ix, iy, rMask, rRect))
>       {
> // do smothing if (ix,iy) is contained in the ROI
>       }
>
> which is much faster!
>
>
> JW
>
>
>
>
>                       Gabriel Landini
>                       <G.Landini@BHAM.         An:      [hidden email]
>                       AC.UK>                   Kopie:
>                       Gesendet von:            Thema:   Re: how to access
> the ROI programmatically? ImageJ Interest
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>                       .GOV>
>
>
>                       03.07.2006 22:20
>                       Bitte antworten
>                       an ImageJ
>                       Interest Group
>
> > I need to do a check for whether or not a certain point/pixel coordinate
>
> is
>
> > contained in the ROI.
> > My code is of the form
> > for all pixels, if pixels is in ROI, do stuff
> > The ROI is a path resulting from freehand selection.
> >
> > I was not able to find such a function in the API documentation. Is there
>
> a
>
> > function like the one I'm describing? Any suggestions on how to implement
>
> it?
>
> There is a method in Roi.java called "contains" which perhaps does what you
>
> need (not entirely sure).
> However if you have many pixels this may be slow.
>
> Alternatively you could create a binary image that has just the filled ROI,
>
> then use this image to direct the analysis (scan this image and all set
> pixels give you the coordinates of the pixels in the original that need to
> be
> processed).
>
> I hope it helps.
>
> Gabriel
>
>
>
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