masking in RGB image

i have a RGB image. I want to know the method to mask a particular area of that image. The area need to be selected by mouse cursor.

Answer 1

[Doug Hull]

impoly

Answer 2

[Image Analyst]

Here's a demo:

% Have user freehand draw a mask in the image.
uiwait(msgbox('Draw a region with left button down.  Double click inside to finish it'));
h = imfreehand();
vertices = wait(h);
% Create a binary mask
mask = createMask(h);
subplot(2,2,1);
imshow(mask, []);
% Mask the image.
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask,class(rgbImage)));
subplot(2,2,2);
imshow(maskedRgbImage);