Java9多解析度影象API

在Java 9中，已經推出了一種新的多解析度影象API，支援具有不同解析度變體的多個影象。 該API允許將具有不同解析度的一組影象用作單個多解析度影象。 以下是多解析度影象的主要操作。

• Image getResolutionVariant(double destImageWidth, double destImageHeight) - 獲取一個特定的影象，這是最好的變體，以指定的尺寸表示這個邏輯影象。
• List<Image> getResolutionVariants() - 獲取所有解析度變體的可讀列表。

範例

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("/20/206/8011.html9/images/logo.png",
         "/20/206/8011.html9/images/mini_logo.png",
         "/20/206/8011.html9/images/large_logo.png");

      List<Image> images = new ArrayList<Image>();

      for (String url : imgUrls) {
         images.add(ImageIO.read(new URL(url)));
      }

      // read all images into one multiresolution image
      MultiResolutionImage multiResolutionImage = 
         new BaseMultiResolutionImage(images.toArray(new Image[0]));

      // get all variants of images
      List<Image> variants = multiResolutionImage.getResolutionVariants();

      System.out.println("Total number of images: " + variants.size());

      for (Image img : variants) {
         System.out.println(img);
      }

      // get a resolution-specific image variant for each indicated size
      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));
   }  
}

執行上面範例程式碼，得到以下結果 -

Total number of images: 3
BufferedImage@7ce6a65d: type = 6 ColorModel: #pixelBits = 32 numComponents = 4 
color space =java.awt.color.ICC_ColorSpace@548ad73b transparency = 3 
has alpha = true isAlphaPre = false ByteInterleavedRaster: width =311 
height = 89 #numDataElements 4 dataOff[0] = 3

BufferedImage@4c762604: type = 6 ColorModel: #pixelBits = 32 numComponents = 4 
color space =java.awt.color.ICC_ColorSpace@548ad73b transparency = 3 
has alpha = true isAlphaPre = false ByteInterleavedRaster: width =156 
height = 45 #numDataElements 4 dataOff[0] = 3

BufferedImage@2641e737: type = 6 ColorModel: #pixelBits = 32 numComponents = 4 
color space =java.awt.color.ICC_ColorSpace@548ad73b transparency = 3 
has alpha = true isAlphaPre = false ByteInterleavedRaster: width =622 
height = 178 #numDataElements 4 dataOff[0] = 3

Image for destination[156,45]: [311,89]
Image for destination[311,89]: [311,89]
Image for destination[622,178]: [622,178]
Image for destination[300,300]: [622,178]