c++ - 在循环中使用 cvtColor

Question

我正在尝试循环运行 cvtColor 命令。

    vector<Mat> RImages;
    vector<Mat> hImages;      

    for ( int idx = 0; idx < blocks_width * blocks_height; idx++ )
    {
        ...
        Mat temp;
        RImages.push_back( imread( filename , 1 ) );
        hImages.push_back( cvtColor( RImages[ idx ], temp , CV_BGR2HSV ));
    }

我收到错误信息:

invalid use of void expression in ctColor.

Answer 1

cvtColor( RImages[ idx ], temp , CV_BGR2HSV )

这个函数不返回任何东西。 cvtColor 的结果存储在临时文件中。你的代码应该是这样的:

vector<Mat> RImages;
vector<Mat> hImages;      

for ( int idx = 0; idx < blocks_width * blocks_height; idx++ )
{
    ...
    Mat temp;
    RImages.push_back( imread( filename , 1 ) );
    cvtColor( RImages[ idx ], temp , CV_BGR2HSV );
    hImages.push_back(temp  );
}

顺便说一句，你可以像这样优化你的代码:

vector<Mat> RImages;
vector<Mat> hImages;
RImages.reserve(blocks_width * blocks_height); 
hImages.reserve(blocks_width * blocks_height); 
for ( int idx = 0; idx < blocks_width * blocks_height; idx++ )
{
    ...
    Mat temp;
    RImages.emplace_back(imread( filename , 1 ) );
    cvtColor( RImages[ idx ], temp , CV_BGR2HSV );
    hImages.emplace_back(temp  );
}