reading an array of images in c++ (using opencv)

Question

I want to read an array of images in c++ and I wrote this sample code:

std::vector<Mat> ReadInputImages()
{
    Mat tmp1=imread("C:/tmp/im1.jpg");
    Mat tmp2=imread("C:/tmp/im2.jpg");
    Mat tmp3=imread("C:/tmp/im3.jpg");
    Mat tmp4=imread("C:/tmp/im4.jpg");
    std::vector<Mat> images;
    images={tmp1,tmp2,tmp3,tmp4};
    return images;
}

But it doesn't work and I am getting compiler error on

   images={tmp1,tmp2,tmp3,tmp4};

What is the best way to return an array of images from a function.

juanchopanza · Accepted Answer · 2013-05-27 11:12:38Z

7

The C++11 initialitzation syntax would be

std::vector<Mat> images={tmp1,tmp2,tmp3,tmp4};

or

std::vector<Mat> images{tmp1,tmp2,tmp3,tmp4};

But you do not need to declare a temporary vector, you can return one directly:

std::vector<Mat> ReadInputImages()
{
  return std::vector<Mat>{imread("C:/tmp/im1.jpg"),
                          imread("C:/tmp/im2.jpg"),
                          imread("C:/tmp/im3.jpg"),
                          imread("C:/tmp/im4.jpg")};
}

If you do not have C++11 support, you can simply push elements back into an existing vector,

std::vector<Mat> ReadInputImages()
{
    std::vector<Mat> images;
    images.push_back(imread("C:/tmp/im1.jpg"));
    images.push_back(imread("C:/tmp/im2.jpg"));
    images.push_back(imread("C:/tmp/im3.jpg"));
    images.push_back(imread("C:/tmp/im4.jpg"));
    return images;
}

edited May 27, 2013 at 11:12

answered May 27, 2013 at 10:59

juanchopanza

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4 Comments

mans Over a year ago

Does visual studio 2012 support c++11?

juanchopanza Over a year ago

@mans my understanding is that it supports a large subset of it. Unfortunately, according to that page, initializer lists isn't part of it.

mans Over a year ago

Thanks. Which page do you referring?

juanchopanza Over a year ago

@mans click on "a large subset of it" in my previous comment.

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