MATLAB: Fspecial Disk Filter Shape

diskfilterfspecialImage Processing Toolbox

What is the actual shape of the pre-defined disk filter in MATLAB? Obviously it can't be exactly circular but what shape would it have with say a radius of 5. For example, the center row I'm guessing would have 9 pixels including the pixel of interest but I'm not sure… What about the other rows? Thanks.

Best Answer

Just type it out and see:

>>theFilter = fspecial('disk', 5)

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MATLAB: Maximising Pixels within Certain area of Matrix

One whose sum of pixel values is the greatest

Convolve your matrix with an array of 1 the same size as the area. The location of the maximum of the convolution is the centre of the area with the highest sum:

areasum = conv2(yourmatrix, ones(5)), 'same');
[~, idx] = max(areasum);
[centrerow, centrecol] = ind2sub(size(yourmatrix), idx)

MATLAB: I couldn’t understand convex area

Hi Selim,

the 'convexArea' property corresponds the area of the convex hull of the region. The convex hull of a region is the smallest region that satisfy two conditions: (1) it is convex (2) it contains the original region.

The convex area is by definition greater than or equal to the area of the region. It can be used to compute a shape factor known either as "convexity" or "solidity", defined as the ratio of area over convex area. It can be obtained by using the 'solidity' parameter in regionprops function.

The solidity can be used to discriminate or classify regions using shape criteria.

regards,

Best Answer

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