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From: Henry Mei on 7 Aug 2010 13:54
I'm basically trying to recursively navigate through all pixels of a line and assign it a height value (double), by converting the grayscale uint8 array to double and then replacing the pixels with a height. I only need to do a 4-neighbor search, and to avoid recurring through already changed pixel, I just use a boolean array to keep track of traversed pixels.

I tested my code using nxn arrays filled with the line intensity I want (i.e. the function should replace all elements of the array); however, MATLAB locks up and crashes when exceed a ~50x50 array. I'd appreciate it if anybody could tell me if I made an error in my code or if there's an iterative solution.

Below is code:

function output = assignHeight(arr, pr, pc, height, thresh)

[m,n] = size(arr);
grid = false(m,n);

function assignH(pr, pc, m, n, height, thresh)

if (pr<=m) && (pc<=n) && (pr>0) && (pc>0) && (arr(pr,pc)>255*thresh) && (grid(pr,pc)==false)
arr(pr,pc) = height;
grid(pr,pc) = true;
assignH(pr,pc+1,m,n,height,thresh);
assignH(pr,pc-1,m,n,height,thresh);
assignH(pr+1,pc,m,n,height,thresh);
assignH(pr-1,pc,m,n,height,thresh);
end
end

assignH(pr, pc, m, n, height, thresh);
output = arr;
end
From: Henry Mei on 7 Aug 2010 14:43
I've found a solution by using bwlabel/bwconncomp. Thanks all for reading.

"Henry Mei" <henry.mei(a)gatech.edu> wrote in message <i3k6e8$3q$1(a)fred.mathworks.com>...
> I'm basically trying to recursively navigate through all pixels of a line and assign it a height value (double), by converting the grayscale uint8 array to double and then replacing the pixels with a height. I only need to do a 4-neighbor search, and to avoid recurring through already changed pixel, I just use a boolean array to keep track of traversed pixels.
>
> I tested my code using nxn arrays filled with the line intensity I want (i.e. the function should replace all elements of the array); however, MATLAB locks up and crashes when exceed a ~50x50 array. I'd appreciate it if anybody could tell me if I made an error in my code or if there's an iterative solution.
>
> Below is code:
>
> function output = assignHeight(arr, pr, pc, height, thresh)
>
> [m,n] = size(arr);
> grid = false(m,n);
>
> function assignH(pr, pc, m, n, height, thresh)
>
> if (pr<=m) && (pc<=n) && (pr>0) && (pc>0) && (arr(pr,pc)>255*thresh) && (grid(pr,pc)==false)
> arr(pr,pc) = height;
> grid(pr,pc) = true;
> assignH(pr,pc+1,m,n,height,thresh);
> assignH(pr,pc-1,m,n,height,thresh);
> assignH(pr+1,pc,m,n,height,thresh);
> assignH(pr-1,pc,m,n,height,thresh);
> end
> end
>
> assignH(pr, pc, m, n, height, thresh);
> output = arr;
> end
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