how to extract the bounding box area as segmented object from video frame?...I have been trying imcrop but the rectangle cropped out is not as same as bbox rectangle.

I am using computer vision toolbox.. this is the code..Is there any other way of doing it??

please help..thankyou in advance!

crop=bbox(:,); % all bbox that hav objects

   crop=transpose(crop);  % bbox as crop in row major as for rectangles

   num = size(crop,1);
    for k = 1: num

             crop(k,2)=crop(k,2)-crop(k,3); % ymin is required but ymax is in upper left corner

temp=crop(k,3); % swapping height and width as required in rectangle! crop(k,3)=crop(k,4); crop(k,4)=temp;

             [Xtest,Ytest,itest,Rtest]=imcrop(image,crop(k,:));
        imshow(itest);

Answer 1

[Image Analyst]

I don't know what bbox is. Don't use image as the name of your image variable because it's the name of a built-in function. Simply crop like this:

croppedImage = imcrop(fullImage, [leftColumn, topRow, numberOfColumns, numberOfRows]);

You have to figure out how to get leftColumn, topRow, numberOfColumns, numberOfRows.

[sania]

Thankyou for the reply..actually m using computer vision system toolbox..After doing blol analysis I got bounding box for the object which is the vehicle in the frames.. This bbox is actually the same bounding box.This is the code..

hblob = vision.BlobAnalysis( ... 'CentroidOutputPort', false, ... 'AreaOutputPort', true, ... 'BoundingBoxOutputPort', true, ... 'OutputDataType', 'single', ... 'NumBlobsOutputPort', false, ... 'MinimumBlobAreaSource', 'Property', ... 'MinimumBlobArea', 250, ... 'MaximumBlobAreaSource', 'Property', ... 'MaximumBlobArea', 3600, ... 'FillValues', -1, ... 'MaximumCount', 80);

 [area, bbox] = step(hblob, fg_image);

So the left column, toprow, no of columns, number of rows that you have told to find to use imcrop is sctually given by this bbox!

But still m not getting the segmented vehicle..The box is drwan correctly but not segmented via imcrop..I think the cordinates are not matching for bbox and imcrop..Please please help..

[Image Analyst]

I don't know what step() does, but in all the MATLAB functions that I can think of when it wants a rectangle, it's [xStart, yStart, xSize, ySize]. Check with the documentation for step() - for example make sure it's not using row, column instead of x,y.

Answer 2

[Anand]

It seems to work for me...The rectangle specification provided by the vision.BlobAnalysis object is the same as that required by imcrop.

im    = padarray(strel('disk',100,0).getnhood,[50 25],'pre');
hblob = vision.BlobAnalysis;

[area,centroid,bbox] = step(hblob,im);

>> bbox

bbox =

            26          51         201         201

out = imcrop(im,bbox);
imshow(out);

[sania]

running the same code giving me this error:

 Error using ==> imageDisplayParsePVPairs at 121
Invalid input arguments.

Error in ==> imageDisplayParseInputs at 70 [common_args,specific_args] = imageDisplayParsePVPairs(varargin{:});

Error in ==> imshow at 199 [common_args,specific_args] = ...

Error in ==> imcrop>parseInputs at 248 imshow(a,cm);

Error in ==> imcrop at 94 [x,y,a,cm,spatial_rect,h_image,placement_cancelled] = parseInputs(varargin{:});

[sania]

I am using matlab R2011? which one you used?