如何在 OpenCV 中对图像进行阈值处理？

Question

我在 OpenCV 中有一个表示掩码的二进制图像。这个蒙版有一定程度的几何噪声，我想平滑，所以我使用模糊来实现这个效果。

现在我有一个灰度图像。我想将高于某个阈值的所有像素设为白色，而所有其他像素必须变为黑色。

在 opencv 中是否有一种简单的方法可以做到这一点？

Answer 1

是的，有：

ret,thresh1 = cv.threshold(img,127,255,cv.THRESH_BINARY)

我来自this link。

在 C++ 上，我们有

threshold( src_gray, dst, threshold_value, max_BINARY_value,threshold_type );

Here if you want further information

上一个链接的完整代码（C++ 教程）

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <stdlib.h>
#include <stdio.h>

using namespace cv;

/// Global variables

int threshold_value = 0;
int threshold_type = 3;;
int const max_value = 255;
int const max_type = 4;
int const max_BINARY_value = 255;

Mat src, src_gray, dst;
char* window_name = "Threshold Demo";

char* trackbar_type = "Type: \n 0: Binary \n 1: Binary Inverted \n 2: Truncate \n 3: To Zero \n 4: To Zero Inverted";
char* trackbar_value = "Value";

/// Function headers
void Threshold_Demo( int, void* );

/**
 * @function main
 */
int main( int argc, char** argv )
{
  /// Load an image
  src = imread( argv[1], 1 );

  /// Convert the image to Gray
  cvtColor( src, src_gray, CV_BGR2GRAY );

  /// Create a window to display results
  namedWindow( window_name, CV_WINDOW_AUTOSIZE );

  /// Create Trackbar to choose type of Threshold
  createTrackbar( trackbar_type,
                  window_name, &threshold_type,
                  max_type, Threshold_Demo );

  createTrackbar( trackbar_value,
                  window_name, &threshold_value,
                  max_value, Threshold_Demo );

  /// Call the function to initialize
  Threshold_Demo( 0, 0 );

  /// Wait until user finishes program
  while(true)
  {
    int c;
    c = waitKey( 20 );
    if( (char)c == 27 )
      { break; }
   }

}


/**
 * @function Threshold_Demo
 */
void Threshold_Demo( int, void* )
{
  /* 0: Binary
     1: Binary Inverted
     2: Threshold Truncated
     3: Threshold to Zero
     4: Threshold to Zero Inverted
   */

  threshold( src_gray, dst, threshold_value, max_BINARY_value,threshold_type );

  imshow( window_name, dst );
}