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  JavaFX - 图像

  • 简述

    您可以使用包中 JavaFX 提供的类加载和修改图像 javafx.scene.image. JavaFX 支持图像格式，如Bmp, Gif, Jpeg, Png.
    本章教您如何将图像加载到 JavaFX、如何在多个视图中投影图像以及如何更改图像的像素。

  • 加载图像

    您可以通过实例化名为的类在 JavaFX 中加载图像 Image 包的 javafx.scene.image.
    对于类的构造函数，您必须传递以下任一参数 -
    • 一个 InputStream 要加载的图像的对象，或者，
    • 保存图像 URL 的字符串变量。 
    
//Passing FileInputStream object as a parameter 
FileInputStream inputstream = new FileInputStream("C:\\images\\image.jpg"); 
Image image = new Image(inputstream); 
         
//Loading image from URL 
//Image image = new Image(new FileInputStream("url for the image));
    加载图像后，您可以通过实例化图像来设置图像的视图 ImageView 类并将图像传递给其构造函数，如下所示 - 
    
ImageView imageView = new ImageView(image);

    例子

    以下是演示如何在 JavaFX 中加载图像并设置视图的示例。
    将此代码保存在名称为的文件中 ImageExample.java. 
    
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;  
import javafx.stage.Stage;  
public class ImageExample extends Application {  
   @Override 
   public void start(Stage stage) throws FileNotFoundException {         
      //Creating an image 
      Image image = new Image(new FileInputStream("path of the image"));  
      
      //Setting the image view 
      ImageView imageView = new ImageView(image); 
      
      //Setting the position of the image 
      imageView.setX(50); 
      imageView.setY(25); 
      
      //setting the fit height and width of the image view 
      imageView.setFitHeight(455); 
      imageView.setFitWidth(500); 
      
      //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, 500);  
      
      //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 static void main(String args[]) { 
      launch(args); 
   } 
}
    使用以下命令从命令提示符编译并执行保存的 java 文件。 
    
Javac ImageExample.java 
java ImageExample
    执行时，上述程序会生成一个 JavaFX 窗口，如下所示 -
    加载图片

  • 图像的多个视图

    您还可以为同一场景中的图像设置多个视图。以下程序是一个示例，演示如何在 JavaFX 中为场景中的图像设置各种视图。
    将此代码保存在名称为的文件中 MultipleViews.java. 
    
import java.io.FileInputStream; 
import java.io.FileNotFoundException; 
import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.image.Image;  
import javafx.scene.image.ImageView; 
import javafx.stage.Stage;  
public class MultipleViews extends Application {  
   @Override 
   public void start(Stage stage) throws FileNotFoundException {         
      //Creating an image 
      Image image = new Image(new FileInputStream("file path"));  
      
      //Setting the image view 1 
      ImageView imageView1 = new ImageView(image); 
      
      //Setting the position of the image 
      imageView1.setX(50); 
      imageView1.setY(25); 
      
      //setting the fit height and width of the image view 
      imageView1.setFitHeight(300); 
      imageView1.setFitWidth(250);         
      
      //Setting the preserve ratio of the image view 
      imageView1.setPreserveRatio(true); 
         
      //Setting the image view 2 
      ImageView imageView2 = new ImageView(image);
      
      //Setting the position of the image 
      imageView2.setX(350); 
      imageView2.setY(25); 
      
      //setting the fit height and width of the image view 
      imageView2.setFitHeight(150); 
      imageView2.setFitWidth(250);          
      
      //Setting the preserve ratio of the image view 
      imageView2.setPreserveRatio(true); 
         
      //Setting the image view 3 
      ImageView imageView3 = new ImageView(image);  
      
      //Setting the position of the image 
      imageView3.setX(350); 
      imageView3.setY(200); 
      
      //setting the fit height and width of the image view 
      imageView3.setFitHeight(100); 
      imageView3.setFitWidth(100);         
      
      //Setting the preserve ratio of the image view 
      imageView3.setPreserveRatio(true);  
      
      //Creating a Group object  
      Group root = new Group(imageView1, imageView2, imageView3);  
      
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 400);  
      
      //Setting title to the Stage 
      stage.setTitle("Multiple views of an image");  
      
      //Adding scene to the stage 
      stage.setScene(scene);  
      
      //Displaying the contents of the stage
      stage.show(); 
   }  
   public static void main(String args[]) { 
      launch(args); 
   } 
}
    使用以下命令从命令提示符编译并执行保存的 java 文件。 
    
Javac MultipleViews.java 
java MultipleViews
    执行时，上述程序会生成一个 JavaFX 窗口，如下所示 -
    多视图

  • 写入像素

    JavaFX 提供名为的类 PixelReader 和 PixelWriter类来读取和写入图像的像素。这WritableImage 类用于创建可写图像。
    以下是演示如何读取和写入图像像素的示例。在这里，我们正在读取图像的颜色值并使其变暗。
    将此代码保存在名称为的文件中 WritingPixelsExample.java. 
    
import java.io.FileInputStream; 
import java.io.FileNotFoundException;  
import javafx.application.Application; 
import javafx.scene.Group;  
import javafx.scene.Scene; 
import javafx.scene.image.Image; 
import javafx.scene.image.ImageView; 
import javafx.scene.image.PixelReader; 
import javafx.scene.image.PixelWriter; 
import javafx.scene.image.WritableImage;
 
import javafx.scene.paint.Color; 
import javafx.stage.Stage;  
public class WritingPixelsExample extends Application {  
   @Override 
   public void start(Stage stage) throws FileNotFoundException {         
      //Creating an image 
      Image image = new Image(new FileInputStream("C:\\images\\logo.jpg")); 
      int width = (int)image.getWidth(); 
      int height = (int)image.getHeight(); 
         
      //Creating a writable image 
      WritableImage wImage = new WritableImage(width, height); 
         
      //Reading color from the loaded image 
      PixelReader pixelReader = image.getPixelReader(); 
      
      //getting the pixel writer 
      PixelWriter writer = wImage.getPixelWriter();           
      
      //Reading the color of the image 
      for(int y = 0; y < height; y++) { 
         for(int x = 0; x < width; x++) { 
            //Retrieving the color of the pixel of the loaded image   
            Color color = pixelReader.getColor(x, y); 
              
            //Setting the color to the writable image 
            writer.setColor(x, y, color.darker());              
         }
      }  
      //Setting the view for the writable image 
      ImageView imageView = new ImageView(wImage); 
              
      //Creating a Group object  
      Group root = new Group(imageView);  
            
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 500);  
            
      //Setting title to the Stage 
      stage.setTitle("Writing pixels ");  
            
      //Adding scene to the stage 
      stage.setScene(scene);  
            
      //Displaying the contents of the stage 
      stage.show();  
   }
   public static void main(String args[]) { 
      launch(args); 
   } 
}
    使用以下命令从命令提示符编译并执行保存的 java 文件。 
    
Javac WritingPixelsExample.java 
java WritingPixelsExample
    执行时，上述程序会生成一个 JavaFX 窗口，如下所示 -
    写入像素
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