Error in opencv code: C++

Question

I am trying to add Gaussian Noise to only a single channel in an image. Here is the code I wrote :

  double Mean = 0.0;
  double StdDev = 10.0;
  Mat gauss_noise = Mat(img_a.size(), CV_16SC1);
  randn(gauss_noise, Scalar::all(Mean), Scalar::all(StdDev));

  Mat img_a_noise_planes[3];
  split(img_a, img_a_noise_planes);
  addWeighted(gauss_noise, 1.0, img_a_noise_planes[1], 1.0, 1.0, img_a_noise_planes[1]);

  merge(img_a_noise_planes, 3, img_a);

I am having an error on the addWeighted() line in the code.
Error:

OpenCV Error: Bad argument (When the input arrays in add/subtract/multiply/divide functions have different types, the output array type must be explicitly specified) in arithm_op, file /home/cortana/Libraries/opencv/modules/core/src/arithm.cpp, line 683
terminate called after throwing an instance of 'cv::Exception'
  what():  /home/cortana/Libraries/opencv/modules/core/src/arithm.cpp:683: error: (-5) When the input arrays in add/subtract/multiply/divide functions have different types, the output array type must be explicitly specified in function arithm_op

Aborted (core dumped)

What am I doing wrong here?

Edit: The color channel value in img_a_noise_planes[1] is 1. So I changed my addweighted() function to :

addWeighted(gauss_noise, 1.0, img_a_noise_planes[1], 1.0, 1.0, img_a_noise_planes[1], 1);

Now the error is :

OpenCV Error: Assertion failed (mv[i].size == mv[0].size && mv[i].depth() == depth) in merge, file /home/cortana/Libraries/opencv/modules/core/src/convert.cpp, line 222
terminate called after throwing an instance of 'cv::Exception'
  what():  /home/cortana/Libraries/opencv/modules/core/src/convert.cpp:222: error: (-215) mv[i].size == mv[0].size && mv[i].depth() == depth in function merge

Aborted (core dumped)

In the merge function, each img_a_noise_planes have channel=1 and I have put 3 in there as img_a has 3 channels and is made by merging.

What is the depth of img_a? Unless it's CV_16SC3, you need to specify the output depth in addWeighted. — beaker
– beaker, Commented Dec 29, 2016 at 21:00

Dusteh · Accepted Answer · 2016-12-29 22:06:35Z

1

I would guess the type of the gaussian Mat is the problem here. If you are not sure of the img_a type then you can move the gauss_noise creation and make it dependent on the type of the split channels. For example:

Mat gauss_noise = Mat(img_a.size(), img_a_noise_planes[1].type());

answered Dec 29, 2016 at 22:06

Dusteh

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2 Comments

Kapil Gupta Over a year ago

I changed my gauss_noise definition, it gives the same error as edit

Kapil Gupta Over a year ago

I removed the changes I had done to addweighted function and it works now. Thanks!

brad · Accepted Answer · 2016-12-29 20:27:05Z

1

Based on the error message it looks like img_a_noise_planes was never initalized or set to the size of the input.

answered Dec 29, 2016 at 20:27

brad

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1 Comment

Dusteh Over a year ago

This is probably not the case since the split should do the required allocation

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