在 Octave 中将长垂直 RGB 图像阵列重塑为分层的水平部分

Question

我正在尝试将一个长的垂直图像数组（多维 RGB 数组）重塑为 Octave 中的分层水平部分。

我有一个很长的垂直图像阵列 (32734x1x3)。 如何重塑图像数组，以便我 将 长垂直图像转换为 52x640x3 的分层水平图像数组，而数组的其余部分用 0 填充以使其“方方正正”

我在查看reshape，但不知道如何在多个维度上重塑数组，同时创建分层的水平部分。

简单示例：数组中剩余的空间用零填充。

我的逻辑/测试是：

a=[1:32734]';

num_cols_wanted=640
num_of_rows_calc=ceil(size(a,1)/num_cols_wanted) %use ceil to get whole number rounded up
num_cells_to_add=mod(size(a,1),num_cols_wanted) %extra cells needed to even array out

b = zeros(num_of_rows_calc, num_cols_wanted); %preallocate 

b=reshape(a,[num_of_rows_calc,num_cols_wanted]); %place reshaped a array into preallocated b array

在测试脚本结束时，我在将原始 array a 重塑为更大的预分配 array b 时遇到问题。我收到一个错误无法重塑 32734x1

PS：我使用的是 Octave 5.2

Answer 1

使用reshape 时，输入元素的数量必须等于输出（重构）元素的数量。

在您的情况下：length(a) 必须等于 num_of_rows_calc*num_cols_wanted。

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执行b = zeros(...) 然后b = reshape(...) 只会覆盖b 的值（用零填充b 没有帮助）。

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• 您可以用零填充b（创建一个“长”向量），并将a 元素复制到a 的开头：

   b = zeros(num_of_rows_calc*num_cols_wanted, 1);
   b(1:length(a)) = a;
  

• 在b的元素数量正确后，我们可以重塑b：

    b = reshape(b, [num_cols_wanted, num_of_rows_calc])';
  

  注意： 在 OCTAVE 中重塑向量首先按列（从上到下）对元素进行排序。
  对于按行排序，我们可以重塑为 cols x 行并转置结果。

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完整的代码示例：

%a=[1:32734]';
a = (1:10)';

num_cols_wanted=3; %640;
num_of_rows_calc=ceil(size(a,1)/num_cols_wanted); %use ceil to get whole number rounded up
num_cells_to_add=mod(size(a,1),num_cols_wanted); %extra cells needed to even array out

b = zeros(num_of_rows_calc*num_cols_wanted, 1); %Create a vector of zeros with desired number of elements.

b(1:length(a)) = a; %Copy a into the b - keeping the zeros at the end of b (we could also add zero padding at the end of a).

%Reshape to num_cols_wanted x num_of_rows_calc and transpose, because OCTAVE ordering is "column major".
b = reshape(b, [num_cols_wanted, num_of_rows_calc])'; %reshape b array into preallocated b array

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结果：

b =

    1    2    3
    4    5    6
    7    8    9
   10    0    0

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3D 输出示例：

a = cat(3, (1:10)', (21:30)', (31:40)');

a = squeeze(a); % Remove redunded dimentsion

num_cols_wanted=4;%640;
num_of_rows_calc=ceil(size(a,1)/num_cols_wanted); %use ceil to get whole number rounded up
num_cells_to_add=mod(size(a,1),num_cols_wanted); %extra cells needed to even array out

b = zeros(num_of_rows_calc*num_cols_wanted, 3); %Create 3 columns matrix of zeros with desired number of elements.

b(1:length(a), :) = a; %Copy a into the b - keeping the zeros at the end of b (we could also add zero padding at the end of a).

%Reshape to 3 x num_cols_wanted x num_of_rows_calc and permute, because OCTAVE ordering is "column major".
b = reshape(b, [num_cols_wanted, num_of_rows_calc, 3]); %reshape b array into preallocated b array
b = permute(b, [2, 1, 3]);