OpenCV彩色图像转为二进制

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2023-03-14

使用threshold()方法将灰度图像转换为二进制值图像。以下是此方法的语法。

threshold(Mat src, Mat dst, double thresh, double maxval, int type)

该方法接受以下参数 -

mat - 表示输入图像的Mat对象。
dst - 表示输出图像的Mat对象。
thresh - 表示阈值的整数。
maxval - 一个整数，表示与THRESH_BINARY和THRESH_BINARY_INV阈值类型一起使用的最大值。
type - 表示转换类型的整数代码，例如RGB到灰度。

通过将代码Imgproc.THRESH_BINARY与值一起传递给其余参数，可以将灰度图像转换为二值图像。

示例

以下程序演示如何将彩色图像作为二进制图像读取并使用JavaFX窗口显示。

package yiibai.com;

import java.awt.image.BufferedImage;

import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;

import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.image.ImageView;
import javafx.scene.image.WritableImage;
import javafx.stage.Stage;

public class ColorToBinary extends Application {
   @Override
   public void start(Stage stage) throws Exception {
      WritableImage writableImage = loadAndConvert();

      // Setting the image view
      ImageView imageView = new ImageView(writableImage);

      // Setting the position of the image
      imageView.setX(10);
      imageView.setY(10);

      // setting the fit height and width of the image view
      imageView.setFitHeight(400);
      imageView.setFitWidth(600);

      // Setting the preserve ratio of the image view
      imageView.setPreserveRatio(true);

      // Creating a Group object
      Group root = new Group(imageView);

      // Creating a scene object
      Scene scene = new Scene(root, 600, 400);

      // Setting title to the Stage
      stage.setTitle("Loading an image");

      // Adding scene to the stage
      stage.setScene(scene);

      // Displaying the contents of the stage
      stage.show();
   }
   public WritableImage loadAndConvert() throws Exception {
      // Loading the OpenCV core library
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME );

      // Instantiating the Imgcodecs class
      Imgcodecs imageCodecs = new Imgcodecs();

      // File input = new File("C:/EXAMPLES/OpenCV/sample.jpg");
      String input = "F:/worksp/opencv/images/sample.jpg";

      // Reading the image
      Mat src = imageCodecs.imread(input);

      // Creating the destination matrix
      Mat dst = new Mat();

      // Converting to binary image...
      Imgproc.threshold(src, dst, 200, 500, Imgproc.THRESH_BINARY);

      // Extracting data from the transformed image (dst)
      byte[] data1 = new byte[dst.rows() * dst.cols() * (int)(dst.elemSize())];
      dst.get(0, 0, data1);

      // Creating Buffered image using the data
      BufferedImage bufImage = new BufferedImage(dst.cols(),dst.rows(), 
         BufferedImage.TYPE_BYTE_GRAY);

      // Setting the data elements to the image
      bufImage.getRaster().setDataElements(0, 0, dst.cols(), dst.rows(), data1);

      // Creating a Writable image
      WritableImage writableImage = SwingFXUtils.toFXImage(bufImage, null);

      System.out.println("Converted to binary");
      return writableImage;
   }  
   public static void main(String args[]) throws Exception {
      launch(args);
   }
}

输入图像，假定以下是上述程序中指定的输入图像sample.jpg。

在执行程序时，您将得到以下输出。