edge parameter calculation

how to use the Sobel edge detection method to detect image edges (IE) is obtained by filtering an input image with two convolution kernels concomitantly, one to detect changes in vertical contrast (hx) and the other to detect horizontal contrast (hy ), shown in equation (1). Image output (IE ) is obtained by calculating the gradient magnitude of each pixel, as shown in equation (2). Subsequently, the edge parameter (E) is calculated, whereby E (r, c) is increased by one each time when IE (x, y) = ‘1’ in a supervised block, as shown in equation (3) Hx = ? ? ? ? ? ? ? ? ? ? ? ? ? 1 0 1 2 0 2 1 0 1 ,Hy = ? ? ? ? ? ? ? ? ? ? ? ? ? 1 2 1 0 0 0 1 2 1 (1) I (x, y) I 2 (x, y) I 2 (x, y) E x y = + (2) ? ? = == x y B E r c IEP ( , ) ( , ) ( 1) (3)

Answer 1

[David Young]

If you have the Image Processing Toolbox, the Sobel edge detector is available as one of the methods implemented in the EDGE function. See

doc edge

[bhargavi]

i have seen this bw=edge(i,'sobel') but i can't get the result

[David Young]

Can you explain what you mean "can't get the result". Is there an error message? I'll make a guess at one possible problem, and suggest you try bw = edge(double(i), 'sobel');

[bhargavi]

bw = edge(double(i), 'sobel'); i have tried this also

unction EDGE expected its first input, I, to be two-dimensional.

Error in ==> edge>parse_inputs at 564

iptcheckinput(I,{'numeric'},{'nonsparse','2d'},mfilename,'I',1);

Error in ==> edge at 197

[a,method,thresh,sigma,thinning,H,kx,ky] = parse_inputs(varargin{:});

>>

[David Young]

So I guess the array i is not two-dimensional. You can use the size function to see whether it is or not.

If the array is three-dimensional because it is an RGB image, you could use rgb2gray to convert it to s 2-D grayscale image.