How to Imply the Input Array Dimensions to MATLAB Coder

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Royi Avital 2019-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/480377-how-to-imply-the-input-array-dimensions-to-matlab-coder

评论： Royi Avital 2020-5-27

Assuming I have a simple function in MATLAB:

function [ mG ] = ProcessImage( mI ) %#codegen
mG = edge(mI, 'Sobel', [], 'both');
end

Now, I want to generate a C code from it.

I also want the C code to work on any 2D Image mI. Yet I don't know the size on compile time. So in C it is solved by sending the dimensions of the array as parameters to the function. Something like:

function [ mG ] = ProcessImage( mI, numRows, numCols ) %#codegen
mG = edge(mI, 'Sobel', [], 'both');
end

Now, my question is, how can I tell MATLAB Coder to understand those parametters are the size of the input image?

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Answer 1

Denis Gurchenkov 2019-9-17

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https://ww2.mathworks.cn/matlabcentral/answers/480377-how-to-imply-the-input-array-dimensions-to-matlab-coder#answer_392180

The closest you can do, I think, is this:

codegen ProcessImage -args {coder.typeof(uint(0), [Inf Inf]) } -config:lib

This would generate ProcessImage.c that takes an unbounded 2-d array of uint8 as input. Coder would also generate main.c (in the examples folder) that shows how to allocate and initialize the data structure that ProcessImage.c takes as input.

From there, you can write a simple wrapper that takes a pointer and two sizes and produces the emxArray_uint8_T data structure that coder-generated code takes as input. You can set the "canFreeData" to false and then you don't need to copy the actual values, can just copy your pointer into the emx structure.

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Royi Avital 2020-4-21

I wish there was more elegant option. I want to generate a function with same signature as you'd do in pure C. So send few pointersa to arrays and integers to hint their dimensions.

Royi Avital 2020-5-27

Dennis, what about the case MATLAB coder doesn't infer the data dimensions correctly in the middle of the code. Is there a way to assist and tell it the data dimensions?

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