Java9多分辨率圖像API

Java 9 定義多分辨率圖像 API，開發者可以很容易的操作和展示不同分辨率的圖像了。

以下是多分辨率圖像的主要操作方法：

• Image getResolutionVariant(double destImageWidth, double destImageHeight) − 獲取特定分辨率的圖像變體-表示一張已知分辨率單位為DPI的特定尺寸大小的邏輯圖像，并且這張圖像是最佳的變體。

• List getResolutionVariants() − 返回可讀的分辨率的圖像變體列表。

import java.io.IOException;
import java.net.URL;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.List;
import java.awt.Image;
import java.awt.image.MultiResolutionImage;
import java.awt.image.BaseMultiResolutionImage;
 
import javax.imageio.ImageIO;
 
public class Tester {
   public static void main(String[] args) throws IOException, MalformedURLException {
 
      List<String> imgUrls = List.of("http://www.dabaquan.cn/wp-content/themes/bjpowernode/assets/img/bjpowernode-logo@2x.png",
         "http://www.dabaquan.cn/wp-content/themes/bjpowernode/assets/img/bjpowernode-logo.png",
         "http://www.dabaquan.cn/wp-content/themes/bjpowernode/assets/images/qrcode.png");
 
      List<Image> images = new ArrayList<Image>();
 
      for (String url : imgUrls) {
         images.add(ImageIO.read(new URL(url)));
      }
 
      // 讀取所有圖片
      MultiResolutionImage multiResolutionImage = 
         new BaseMultiResolutionImage(images.toArray(new Image[0]));
 
      // 獲取圖片的所有分辨率
      List<Image> variants = multiResolutionImage.getResolutionVariants();
 
      System.out.println("Total number of images: " + variants.size());
 
      for (Image img : variants) {
         System.out.println(img);
      }
 
      // 根據不同尺寸獲取對應的圖像分辨率
      Image variant1 = multiResolutionImage.getResolutionVariant(156, 45);
      System.out.printf("\nImage for destination[%d,%d]: [%d,%d]", 
         156, 45, variant1.getWidth(null), variant1.getHeight(null));
 
      Image variant2 = multiResolutionImage.getResolutionVariant(311, 89);
      System.out.printf("\nImage for destination[%d,%d]: [%d,%d]", 311, 89, 
         variant2.getWidth(null), variant2.getHeight(null));
 
      Image variant3 = multiResolutionImage.getResolutionVariant(622, 178);
      System.out.printf("\nImage for destination[%d,%d]: [%d,%d]", 622, 178, 
         variant3.getWidth(null), variant3.getHeight(null));
 
      Image variant4 = multiResolutionImage.getResolutionVariant(300, 300);
      System.out.printf("\nImage for destination[%d,%d]: [%d,%d]", 300, 300, 
         variant4.getWidth(null), variant4.getHeight(null));
   }  
}