OpenCV中threshold函數的使用

轉自：https://blog.csdn.net/u012566751/article/details/77046445

一篇很好的介紹threshold文章；

圖像的二值化就是將圖像上的像素點的灰度值設置為0或255，這樣將使整個圖像呈現出明顯的黑白效果。在數字圖像處理中，二值圖像占有非常重要的地位，圖像的二值化使圖像中數據量大為減少，從而能凸顯出目標的輪廓。OpenCV中提供了函數cv::threshold();

 

注意:作者采用OpenCV 3.0.0

 

函數原型

 

參數說明

src：源圖像，可以為8位的灰度圖，也可以為32位的彩色圖像。（兩者由區別）

dst：輸出圖像

thresh：閾值

maxval：dst圖像中最大值

type：閾值類型，可以具體類型如下：

編號	閾值類型枚舉	注意
1	THRESH_BINARY
2	THRESH_BINARY_INV
3	THRESH_TRUNC
4	THRESH_TOZERO
5	THRESH_TOZERO_INV
6	THRESH_MASK	不支持
7	THRESH_OTSU	不支持32位
8	THRESH_TRIANGLE	不支持32位

具體如下表

 

生成關系如下表

 

函數參考可以至 http://docs.opencv.org/3.0.0/examples.html

 

測試代碼

Mat gray;

    cvtColor(src, gray, CV_BGR2GRAY); 

    // 全局二值化

    int th = 100;

    cv::Mat threshold1,threshold2,threshold3,threshold4,threshold5,threshold6,threshold7,threshold8;

    cv::threshold(gray, threshold1, th, 255, THRESH_BINARY);

    cv::threshold(gray, threshold2, th, 255, THRESH_BINARY_INV);

    cv::threshold(gray, threshold3, th, 255, THRESH_TRUNC);

    cv::threshold(gray, threshold4, th, 255, THRESH_TOZERO);

    cv::threshold(gray, threshold5, th, 255, THRESH_TOZERO_INV);

    //cv::threshold(gray, threshold6, th, 255, THRESH_MASK);

    cv::threshold(gray, threshold7, th, 255, THRESH_OTSU);

    cv::threshold(gray, threshold8, th, 255, THRESH_TRIANGLE);

    cv::imshow("THRESH_BINARY", threshold1);

    cv::imshow("THRESH_BINARY_INV", threshold2);

    cv::imshow("THRESH_TRUNC", threshold3);

    cv::imshow("THRESH_TOZERO", threshold4);

    cv::imshow("THRESH_TOZERO_INV", threshold5);

    //cv::imshow("THRESH_MASK", threshold6);

    cv::imshow("THRESH_OTSU", threshold7);

    cv::imshow("THRESH_TRIANGLE", threshold8);

    cv::waitKey(0);