十六、Java 9 新特性 – 多分辨率图像 API

Java 9 引入了一种新的多分辨率图像 API，它支持具有不同分辨率变体的多个图像

这些API 允许将具有不同分辨率的一组图像用作单个多分辨率图像

接下来我们就来看看两个 API 如何使用吧。

假设存在三张图片

它们的地址分别为

https://pottercoding.cn/static/upload/img/2018/09/03/20180903060845_4.png
https://pottercoding.cn/static/upload/img/2018/09/03/20180903060900_4.png
https://pottercoding.cn/static/upload/img/2018/09/03/20180903060914_4.png

在当前的工作区中创建一个文件 MultiResolutionTester.java 并输入以下内容

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 MultiResolutionTester {
   public static void main(String[] args) throws IOException, MalformedURLException {
      List<String> imgUrls = List.of("https://pottercoding.cn/static/upload/img/2018/09/03/20180903060845_4.png",
         "https://pottercoding.cn/static/upload/img/2018/09/03/20180903060900_4.png",
         "https://pottercoding.cn/static/upload/img/2018/09/03/20180903060914_4.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));
   }  

运行结果如下

[penglei@pottercoding.cn java9]$ javac MultiResolutionTester.java && java MultiResolutionTester
Total number of images: 3
BufferedImage@c267ef4: type = 6 ColorModel:pixelBits = 32 numComponents = 4 color space = java.awt.color.ICC_ColorSpace@32eff876 transparency = 3 has alpha = true isAlphaPre = false ByteInterleavedRaster: width = 32 height = 32numDataElements 4 dataOff[0] = 3
BufferedImage@9f116cc: type = 6 ColorModel:pixelBits = 32 numComponents = 4 color space = java.awt.color.ICC_ColorSpace@32eff876 transparency = 3 has alpha = true isAlphaPre = false ByteInterleavedRaster: width = 64 height = 64numDataElements 4 dataOff[0] = 3
BufferedImage@12468a38: type = 6 ColorModel:pixelBits = 32 numComponents = 4 color space = java.awt.color.ICC_ColorSpace@32eff876 transparency = 3 has alpha = true isAlphaPre = false ByteInterleavedRaster: width = 128 height = 128numDataElements 4 dataOff[0] = 3
Image for destination[156,45]: [128,128]
Image for destination[311,89]: [128,128]
Image for destination[622,178]: [128,128]
Image for destination[300,300]: [128,128]

可以看到，这些 API 还会非常的有趣的