How do I crop out a certain part within a matrix of numbers?

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)

[Matt J]

And what should the result look like?

Answer 1

[Chunru]

Are you looking for this?

A = [1 2 3 4 5 ;
       4 9 6 3 9;
       2 5 4 1 3
]

A = 3×5

1 2 3 4 5 4 9 6 3 9 2 5 4 1 3

B = A(2:3, 3:5)

B = 2×3

6 3 9 4 1 3

%% 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)

mx = 6

nx = 6

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)

Y = 4×4

8 4 2 3 7 8 2 3 4 6 9 1 7 9 1 7

[Steven Gangano]

Yes, but I would like to make it more dynamic for any sized matrix. If if I input the boundaries into the function: rowTopLeft, colTopLeft, rowBotRight, colBotRight

The output(resultMatrix) should be all numbers within the boundaries of the input.

Basically if I had a matrix (origImageMatrix):

 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

If wanted to crop out(resultMatrix):

 8 4 2 3
 7 8 2 3
 4 6 9 1
 7 9 1 7

My input would be the borders: rowTopLeft = 8 4 2 3 colTopLeft = 8 7 4 7 rowBotRight = 7 1 9 7 colBotRight = 7 1 3 3

[Chunru]

See update above.

[Steven Gangano]

Thank you! But I just realized that it just needs to be corner coordinates and it can be one line of code. How do you do that? Top left and bottom right coordinates.