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📜  Java DIP-OpenCV灰度转换

📅  最后修改于: 2020-12-14 05:45:34             🧑  作者: Mango

为了使用OpenCV将彩色图像转换为灰度图像，我们将图像读取为BufferedImage并将其转换为Mat对象。其语法如下-

File input = new File("digital_image_processing.jpg");
BufferedImage image = ImageIO.read(input);
//convert Buffered Image to Mat.

然后，可以使用Imgproc类中的方法cvtColor()将图像从RGB转换为灰度格式。其语法如下-

Imgproc.cvtColor(source mat, destination mat1, Imgproc.COLOR_RGB2GRAY);

方法cvtColor()采用三个参数，分别是源图像矩阵，目标图像矩阵和颜色转换类型。

除了cvtColor方法外，Imgproc类还提供其他方法。它们在下面列出-

Sr.No. Method & Description
1

cvtColor(Mat src, Mat dst, int code, int dstCn)

It converts an image from one color space to another.
2

dilate(Mat src, Mat dst, Mat kernel)

It dilates an image by using a specific structuring element.
3

equalizeHist(Mat src, Mat dst)

It equalizes the histogram of a grayscale image.
4

filter2D(Mat src, Mat dst, int depth, Mat kernel, Point anchor, double delta)

It convolves an image with the kernel.
5

GaussianBlur(Mat src, Mat dst, Size ksize, double sigmaX)

It blurs an image using a Gaussian filter.
6

integral(Mat src, Mat sum)

It calculates the integral of an image.

例

以下示例演示了如何使用Imgproc类将图像转换为灰度-

import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;

import java.io.File;
import javax.imageio.ImageIO;

import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.imgproc.Imgproc;

public class Main {
   public static void main( String[] args ) { 
   
      try {
         System.loadLibrary( Core.NATIVE_LIBRARY_NAME );
         File input = new File("digital_image_processing.jpg");
         BufferedImage image = ImageIO.read(input);    

         byte[] data = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
         Mat mat = new Mat(image.getHeight(), image.getWidth(), CvType.CV_8UC3);
         mat.put(0, 0, data);

         Mat mat1 = new Mat(image.getHeight(),image.getWidth(),CvType.CV_8UC1);
         Imgproc.cvtColor(mat, mat1, Imgproc.COLOR_RGB2GRAY);

         byte[] data1 = new byte[mat1.rows() * mat1.cols() * (int)(mat1.elemSize())];
         mat1.get(0, 0, data1);
         BufferedImage image1 = new BufferedImage(mat1.cols(),mat1.rows(), BufferedImage.TYPE_BYTE_GRAY);
         image1.getRaster().setDataElements(0, 0, mat1.cols(), mat1.rows(), data1);

         File ouptut = new File("grayscale.jpg");
         ImageIO.write(image1, "jpg", ouptut);
         
      } catch (Exception e) {
         System.out.println("Error: " + e.getMessage());
      }
   }
}

输出

当执行给定的示例时，它将图像名称digital_image_processing.jpg转换为等效的灰度图像，并将其写入名称为grayscale.jpg的硬盘上。

原始图片

OpenCV灰度转换教程

灰度图像

OpenCV灰度转换教程