问题
I'm trying to implement an algorithm that needs a circular sliding window, that goes through all the pixels of the image, and for each window I need to extract only pixels that lay on diameters at different angles of the circle.
I try to explain better with the use of the image above. Imagine that this is the result of a circular sliding window, I want to get only the pixel values that lay on the red line (diameter tilted of pi/8).
So far, I wrote these lines of code:
I= imread('lena.png');
I = im2double(I);
h = fspecial('disk',5);
h = h > 0;
dir = pi/8;
o_image = blockproc(I, [1 1], @(x) MMF2D(x,h,dir), 'BorderSize', [5 5],...
'TrimBorder', false, 'PadPartialBlocks', true);
and the function MMF2D
:
function [ o_pixel ] = MMF2D( i_block, i_window, i_directions)
%MMF2D Summary of this function goes here
% Detailed explanation goes here
new_block = i_block.data .* i_window;
But from here, I don't know how to continue for getting pixels that lay on diameter. The diameter can be tilted of any angle. Any help is greatly appreciated!
回答1:
Here's what I'd do:
First create the mask (you can put this into a function if you want), and get the relevant pixels indices as function of angle:
%% create mask and get indices as function of angle
o=5;
m=zeros(2*o+1);
m(o+1,:)=1;
theta=0:15:90; % in degrees, theres no need to go beyond 90 deg becuase of symmetry
for n=1:numel(theta)
id{n}=find(imrotate(m,theta(n),'nearest','crop'));
end;
I use a cell array because there can be different number of indices per angle.
Then read image
I= imread('http://scipy-lectures.github.io/_images/lena.png');
Rearrange image blocks into columns
B = im2col(I,[2*o+1 2*o+1],'sliding');
what you want is just:
for n=1:numel(theta)
C{n} = B(id{n},:);
end
each cell element in C represents the pixels that were on a diameter of length 2*o+1
at an angle theta
that was per-defined, for each pixel in the image.
So C{1}
will give you all the pixels for theta=0
, and C{2}
for theta=15
etc...
来源:https://stackoverflow.com/questions/31297554/matlab-circular-sliding-window-and-pixel-values-on-diameters-extraction