How do I crop out a certain part within a matrix of numbers?
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Steven Gangano
il 18 Apr 2022
Commentato: Steven Gangano
il 19 Apr 2022
This example is a small matrix, but I would like to crop out part of this matrix.
The part I want to crop out is: a(2,3:5) and a(3,3:5) which is part of row 2: 639 and underneath it is row 3: 413.
A = [1 2 3 4 5 ;
4 9 6 3 9;
2 5 4 1 3
];
I want to achieve this using the following function below.
Input parameters:
origImageMatrix = A
rowTopLeft = a(2, 3:5) => 6 3 9
colTopLeft = a(2:3, 3) => 6 4
rowBotRight = a(3,5:-1:3) => 3 1 4
colBotRight = a(3:-1:2,5) => 3 9
function [resultMatrix] = cropImg( origImageMatrix, rowTopLeft, colTopLeft, rowBotRight, colBotRight)
Risposta accettata
Chunru
il 18 Apr 2022
Modificato: Chunru
il 18 Apr 2022
Are you looking for this?
A = [1 2 3 4 5 ;
4 9 6 3 9;
2 5 4 1 3
]
B = A(2:3, 3:5)
%% More general
X = [1 2 5 9 2 7
4 8 4 2 3 0
2 7 8 2 3 0
2 4 6 9 1 3
2 7 9 1 7 2
4 8 9 2 1 3];
% My input would be the borders:
% Are you sure you want to have border numbers (which you need to search
% from X) instead of the corner coordinates?
%
% Anyway, here you can search the matrix for border numbers (it may not be
% robust if there are multiple matches)
%
% You just need two borders actually
rowTop = [8 4 2 3];
rowBot = [7 9 1 7];
colLeft = [8 7 4 7];
colRight = [3 3 1 7];
[mx, nx] = size(X)
for i=1:mx
k = strfind(X(i, :), rowTop);
if ~isempty(k)
r1 = i; c1 = k;
break
end
end
for i=1:mx
k = strfind(X(i, :), rowBot);
if ~isempty(k)
r2 = i; c1 = k;
break
end
end
c2 = c1 + length(rowBot) - 1;
Y = X(r1:r2, c1:c2)
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