MATLAB: How does fspecial average filter deal with overlap causes by edges of an image

averageedgefilterfspecialimageImage Processing Toolbox

I am applying an average filter using the fspecial command. I am wondering how the average filter works on images whose dimensions are not multiples of the user-specified hsize. For example if a 3×3 filter is chosen and applied to a 10×10 pixel image, how does this filter deal with the last row and column?

Best Answer

The filter is always centered on the pixel to be processed. At the boundary, missing values are by default replaced by zero.

    imfilter(ones(10), ones(3))

Other boundary conditions can be found at the help of imfilter, e.g., 'replicate', which takes the missing values from the nearest border pixel:

    imfilter(ones(10), ones(3), 'replicate')

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MATLAB: How to apply a window on an image to keep the part in the window while reduce the resolution (clarity) of the remaining part of the picture

Use poly2mask() to make a mask of the part you want to preserve. Then blur the whole image with imfilter() or conv2(). Then replace the image in the mask with the original. Something like

[rows, columns, numberOfColorChannels] = size(grayImage);
mask = poly2mask(x, y, rows, columns);
kernel = ones(9,9);
kernel = kernel / sum(kernel(:)); % Normalize so we don't change the mean intensity of the image.
blurredImage = conv2(grayImage, kernel, 'same'); % Blurs everything, including the masked region.
blurredImage(mask) = grayImage(mask); % Restore original to the masked region.

x and y are the points of the vertices of your trapezoid.

MATLAB: Reducing intensity in an image using a function

https://www.mathworks.com/help/images/ref/medfilt2.html

Best Answer

Related Solutions

MATLAB: How to apply a window on an image to keep the part in the window while reduce the resolution (clarity) of the remaining part of the picture

MATLAB: Reducing intensity in an image using a function

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