Usage of Step Function in Matlab Coder?

Question

Sharan Duggirala 2015-3-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/184711-usage-of-step-function-in-matlab-coder

回答： Jonas Kandume 2020-11-13

An excerpt of my code shown below:

%  Creating the detector for the face 
detector = vision.CascadeObjectDetector; 
%  Bounding Box for face
A = step(detector,I);

This basically doesn't work in the MATLAB coder as it says that A is undefined. The exact error is below:

"Undefined function or variable 'A'. The first assignment to a local variable determines its class."

If I use zeros and preallocate A, step just redefines it. Has anyone gotten around this?

Hope someone can help me on this one!

2 个评论
显示无隐藏无

Denis Gurchenkov 2015-3-30

编辑：Denis Gurchenkov 2015-3-30

在 MATLAB Online 中打开

I did the following:

- Saved this test into test.m:

function A = test
I = 1;
detector = vision.CascadeObjectDetector; 
A = step(detector,I); 
end

- Typed this in MATLAB propmpt:

codegen test

It successfully compiled and produced test_mex in bot 2014b and 2014a releases. Can you show what did you do to get the error? Which release of MATLAB you are using?

Sharan Duggirala 2015-3-31

编辑：Sharan Duggirala 2015-3-31

I seem to be getting these errors. Thank you for your help!

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Denis Gurchenkov 2015-4-1

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/184711-usage-of-step-function-in-matlab-coder#answer_173589

在 MATLAB Online 中打开

Replace the assert statements with the following:

assert(isa(I, 'uint8'));
assert(size(I, 1) < 100);
assert(size(I, 2) < 100);
assert(size(I, 3) == 3);

This will make your example compile fine.

The catch here is that CascadeObjectDetector requires the input's 3rd dimension to be exactly 3. That is, the input must be NxMx3 array. Therefore the assert that size(I,3) == 3 is required.

Also, for code generation, CascadeObjectDetector requires the size of the input to be bounded. There fore the asserts for size(I,1) < 100 and size(I,2) < 100 are required. Of course you can change 100 to some other number, it just has to be some concrete number.

Does this make sense?

Denis.

function [rect] = bound(I)
  assert(isa(I, 'uint8'));
  assert(size(I, 1) < 100);
  assert(size(I, 2) < 100);
  assert(size(I, 3) == 3);
  detector = vision.CascadeObjectDetector;
  A = step(detector, I);
  rect = zeros(1,4);
  rect = [A(1,1), A(1,2), A(1,3), A(1,4)];
end