OpenCV:读取矩阵值

Question

我想计算背景图像中只有黑色和白色的白点数.我有这样的代码:

int count = 0; 
for ( int j = 0; j < Image.rows; j ++ )
    {
    for ( int i = 0; i < Image.cols; i ++ )
        {
            if ( Image.at<int>(i,j) >= 150 )
            {
                count ++ ;
            }
        }
    }

出于某种原因,上面的代码不起作用,它只是停止反应.我检查了,"if(Image.at(i,j)> = 150)"这一行导致了问题.我的"图像"是"cv :: Mat",带有"CV_8UC3"类型.有人可以帮助我吗？谢谢.

Answer 1

除了我对Robin的回答的评论之外,您的错误是您尝试以int为单位访问CV_8UC3类型的图像.如果要检查灰度级别,请执行以下操作(请注意"unsigned char"而不是"int",如Robin的答案).

cv::Mat greyscale;
cv::cvtColor(image,grayscale,CV_RGB2GRAY);
// either, most elegant:
int count = cv::countNonZero(greyscale >= 150);
// or, copied from Robin's answer:
int count = 0;
for(int i = 0; i < greyscale.rows; ++i) {
    const unsigned char* row = greyscale.ptr<unsigned char>(i);
    for(int j = 0; j < greyscale.cols; j++) {
        if (row[j] >= 150)
            ++count;
    }
}

Answer 2

我相信这更整洁:

Mat result;
threshold(Image,result,150,255,THRESH_BINARY);
int white_count = countNonZero(result);