How to replace Nonscalar struct for Matlab Coder error?

Question

WanYu 2020-5-7

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/523723-how-to-replace-nonscalar-struct-for-matlab-coder-error

评论： David Fink 2020-5-11

Hi,

When I'm trying to transform my Matlab code to C, this error appeared yet I don't know how to modify it as it necessary in my function.

%% Remove small objects.
binaryImage = imclearborder(binaryImage);
binaryImage = bwareaopen(binaryImage, 100);
%% Invert the binarized image 
% binaryImage = ~ binaryImage;
%% Get centroid on image
stats = regionprops(binaryImage, 'Centroid');  % acting on the cleaned image
centroids = cat(1, stats.Centroid);
x1 = centroids(1,1);
y1 = centroids(1,2);
x3 = centroids(3,1);
y3 = centroids(3,2);

The error " Directly accessing field or property of nonscalar struct or object not supported for code generation" showed at

centroids = cat(1, stats.Centroid);

How I can resolved it as it is necessary for my function.

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Answer 1

David Fink 2020-5-8

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/523723-how-to-replace-nonscalar-struct-for-matlab-coder-error#answer_431290

在 MATLAB Online 中打开

centroids = cat(1, stats.Centroid);

is just concatenating the centroid row vectors in the first dimension (vertical), which can be replaced by a loop:

numRegions = numel(stats);
centroids = zeros(numRegions, numel(stats(1).Centroid)); % pre-initialize to set size
for region = 1:numRegions
    centroids(region, :) = stats(region).Centroid; % write one row at a time
end

We are looking to allow the original syntax in a future release of MATLAB Coder!