展開並裁剪矩陣

Question

如何在邊緣周圍用零填充矩陣，然後在一些操作後將其裁剪回相同的大小？

Answer 1

你可以這樣做：

octave:1> x = ones(3, 4) 
x = 

    1 1 1 1 
    1 1 1 1 
    1 1 1 1 

octave:2> y = zeros(rows(x)+2, columns(x)+2); 
octave:3> y(2:rows(x)+1, 2:columns(x)+1) = x 
y = 

    0 0 0 0 0 0 
    0 1 1 1 1 0 
    0 1 1 1 1 0 
    0 1 1 1 1 0 
    0 0 0 0 0 0 

octave:4> y = y.*2 (manipulation) 
y = 

    0 0 0 0 0 0 
    0 2 2 2 2 0 
    0 2 2 2 2 0 
    0 2 2 2 2 0 
    0 0 0 0 0 0 

octave:5> x = y(2:rows(x)+1, 2:columns(x)+1) 
x = 

    2 2 2 2 
    2 2 2 2 
    2 2 2 2 

Answer 2

要墊一個數組，你可以使用PADARRAY，如果您有圖像處理工具箱。

否則，你可以墊和收縮方式如下：

smallArray = rand(10); %# make up some random data 
border = [2 3]; %# add 2 rows, 3 cols on either side 

smallSize = size(smallArray); 

%# create big array and fill in small one 
bigArray = zeros(smallSize + 2*border); 
bigArray(border(1)+1:end-border(1),border(2)+1:end-border(2)) = smallArray; 

%# perform calculation here 

%# crop the array 
newSmallArray = bigArray(border(1)+1:end-border(1),border(2)+1:end-border(2));