如何在MATLAB中将图像分成块？ [英] How to divide an image into blocks in MATLAB?

问题描述

我有256x256的图像，我想把它分成4个128x128的块，并将它们作为A1到A4进行处理。现在我想分别调用它们并对它们进行一些操作。我知道这可以使用 blkproc 函数完成 - 但究竟是怎么做的？

I have a 256x256 image and I want to divide it into 4 blocks of 128x128 each and address them as A1 to A4. Now I want to call them separately and do some operations on them. I know this can be done using the blkproc function -- but how exactly?

我是否打电话给 blkproc 喜欢这个？

Do I call blkproc like this?

B=blkproc(I,[4 4],?)

我应该用什么代替？，如何解决4个块创建？

What do I put in place of the "?", and how can I address the 4 blocks created?

推荐答案

自 blockproc （以及弃用的 blkproc ）都是函数在图像处理工具箱中，我想我会添加一个基本的MATLAB解决方案，需要没有额外的工具箱......

Since blockproc (and the deprecated blkproc) are both functions in the Image Processing Toolbox, I thought I'd add a basic MATLAB solution that requires no additional toolboxes...

如果你想将矩阵划分为子矩阵，一种方法是使用 mat2cell 打破矩阵并存储每个子矩阵i n单元阵列的单元格。对于您的情况，语法如下所示：

If you want to divide a matrix into submatrices, one way is to use mat2cell to break the matrix up and store each submatrix in a cell of a cell array. For your case, the syntax would look like this:

C = mat2cell(I, [128 128], [128 128]);

C 现在是2-by- 2个单元阵列，每个单元存储一个128×128的子矩阵 I 。如果要对每个单元格执行操作，则可以使用 cellfun 。例如，如果您想获取每个子矩阵中值的平均值，您将执行以下操作：

C is now a 2-by-2 cell array with each cell storing a 128-by-128 submatrix of I. If you want to perform an operation on each cell, you could then use the function cellfun. For example, if you wanted to take the mean of the values in each submatrix, you would do the following:

meanValues = cellfun(@(x) mean(x(:)), C);

第一个参数是函数句柄到匿名函数，它首先将每个子矩阵重新整形为一个列向量，然后取平均值。输出是每个子矩阵的平均值的2乘2矩阵。如果传递给 cellfun 的函数为每个单元格创建不同大小或类型的输出，那么 cellfun 将出现问题连接它们并将抛出错误：

The first argument is a function handle to an anonymous function which first reshapes each submatrix into a column vector and then takes the mean. The output is a 2-by-2 matrix of the mean values for each submatrix. If the function you pass to cellfun creates outputs of different sizes or types for each cell, then cellfun will have a problem concatenating them and will throw an error:

??? Error using ==> cellfun
Non-scalar in Uniform output, at index 1, output 1.
Set 'UniformOutput' to false.

如果添加 ...，'UniformOutput'，false）; 在您调用 cellfun 结束时，上述情况下的输出将改为2乘2 单元格数组包含在每个子矩阵上执行操作的结果。

If you add ..., 'UniformOutput', false); to the end of your call to cellfun, then the output in the above case will instead be a 2-by-2 cell array containing the results of performing the operation on each submatrix.

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