Thread Subject: how to select a circular region ?

hi,

I can select a rectangular region as ,

I(32:27, 92:82) and change the intensity value of the this region. But I want to select a cicular or ellipsoid region and change its intensity

how to do this?

"Diana " <diana89@yahoo.com> wrote in message <h39tip$2ov$1@fred.mathworks.com>...
> hi,
>
> I can select a rectangular region as ,
>
> I(32:27, 92:82) and change the intensity value of the this region. But I want to select a cicular or ellipsoid region and change its intensity
>
> how to do this?

You must setect the indices (using logical indexing, or FIND indexing) that meet whatever the criteria you chose (inside whatever shape). Example:

I = peaks(40);

[ny nx] = size(I);
x = linspace(-1,1,nx);
y = linspace(-1,1,ny);
[X Y] = meshgrid(x,y);
radius=0.5;
I(X.^2+Y.^2<radius^2)=5; % logical indexing of the circle centered at (0,0)

imagesc(I)

"Bruno Luong" <b.luong@fogale.findmycountry> wrote in message <h39usk$ssd$1@fred.mathworks.com>...
> "Diana " <diana89@yahoo.com> wrote in message <h39tip$2ov$1@fred.mathworks.com>...
> > hi,
> >
> > I can select a rectangular region as ,
> >
> > I(32:27, 92:82) and change the intensity value of the this region. But I want to select a cicular or ellipsoid region and change its intensity
> >
> > how to do this?
>
> You must setect the indices (using logical indexing, or FIND indexing) that meet whatever the criteria you chose (inside whatever shape). Example:
>
> I = peaks(40);
>
> [ny nx] = size(I);
> x = linspace(-1,1,nx);
> y = linspace(-1,1,ny);
> [X Y] = meshgrid(x,y);
> radius=0.5;
> I(X.^2+Y.^2<radius^2)=5; % logical indexing of the circle centered at (0,0)
>
> imagesc(I)

Hi,

I have an image sized 400x400 and want to select ( or add) a circular region on the image. The size of the circular part can be 40x40 like the above code. The above code is very nice, but, how to add this circule onto my image?

"Jan Jaim" <bluekidresat@gmail.com> wrote in message <h3hbf9$hv7$1@fred.mathworks.com>...

> I have an image sized 400x400 and want to select ( or add) a circular region on the image. The size of the circular part can be 40x40 like the above code. The above code is very nice, but, how to add this circule onto my image?
-----------------


How is "adding" a circle to the image a different operation from setting the pixels in the circle to some prominently visible intensity level, as Bruno showed you how to do?

"Matt " <xys@whatever.com> wrote in message <h3hc21$pc8$1@fred.mathworks.com>...
> "Jan Jaim" <bluekidresat@gmail.com> wrote in message <h3hbf9$hv7$1@fred.mathworks.com>...
>
> > I have an image sized 400x400 and want to select ( or add) a circular region on the image. The size of the circular part can be 40x40 like the above code. The above code is very nice, but, how to add this circule onto my image?
> -----------------
>
>
> How is "adding" a circle to the image a different operation from setting the pixels in the circle to some prominently visible intensity level, as Bruno showed you how to do?

Let say the image is;
img=zeros(400,400);

and the above circle is I, and we want to see the circle as

 img(32:72, 92:132)=I; but as you guess the error is,
"Subscripted assignment dimension mismatch". What is the solution ?

"Jan Jaim" <bluekidresat@gmail.com> wrote in message <h3hf96$egd$1@fred.mathworks.com>...
> "Matt " <xys@whatever.com> wrote in message <h3hc21$pc8$1@fred.mathworks.com>...
> > "Jan Jaim" <bluekidresat@gmail.com> wrote in message <h3hbf9$hv7$1@fred.mathworks.com>...
> >
> > > I have an image sized 400x400 and want to select ( or add) a circular region on the image. The size of the circular part can be 40x40 like the above code. The above code is very nice, but, how to add this circule onto my image?
> > -----------------
> >
> >
> > How is "adding" a circle to the image a different operation from setting the pixels in the circle to some prominently visible intensity level, as Bruno showed you how to do?
>
> Let say the image is;
> img=zeros(400,400);
>
> and the above circle is I, and we want to see the circle as
>
> img(32:72, 92:132)=I; but as you guess the error is,
> "Subscripted assignment dimension mismatch". What is the solution ?

dear Jan,
you must check the matrix dimension !

Hi everybody,

I have a grayscale image, let's say it is 400x400. I will show the above white circle onto the grayscale image. But when I write the code as;

grayscaleImg(32:71, 92:131) = I; then the circle seems as black and in the rectangular shape. How to show the circle without the rectangule background and the color of the circle must be white ?

many many thanks..

"Rose Watchy" <Rose.Watchy@gmail.com> wrote in message <h3hpl3$d1e$1@fred.mathworks.com>...
> "Jan Jaim" <bluekidresat@gmail.com> wrote in message <h3hf96$egd$1@fred.mathworks.com>...
> > "Matt " <xys@whatever.com> wrote in message <h3hc21$pc8$1@fred.mathworks.com>...
> > > "Jan Jaim" <bluekidresat@gmail.com> wrote in message <h3hbf9$hv7$1@fred.mathworks.com>...
> > >
> > > > I have an image sized 400x400 and want to select ( or add) a circular region on the image. The size of the circular part can be 40x40 like the above code. The above code is very nice, but, how to add this circule onto my image?
> > > -----------------
> > >
> > >
> > > How is "adding" a circle to the image a different operation from setting the pixels in the circle to some prominently visible intensity level, as Bruno showed you how to do?
> >
> > Let say the image is;
> > img=zeros(400,400);
> >
> > and the above circle is I, and we want to see the circle as
> >
> > img(32:72, 92:132)=I; but as you guess the error is,
> > "Subscripted assignment dimension mismatch". What is the solution ?
>
> dear Jan,
> you must check the matrix dimension !
>
> Hi everybody,
>
> I have a grayscale image, let's say it is 400x400. I will show the above white circle onto the grayscale image. But when I write the code as;
>
> grayscaleImg(32:71, 92:131) = I; then the circle seems as black and in the rectangular shape. How to show the circle without the rectangule background and the color of the circle must be white ?
>
> many many thanks..

Is there anybody who can give answer to this question?
cheers,