Java - 多解析度影像API

多解析度影像 API 在 Java 9 中引入。此 API 支援具有不同解析度變體的多個影像。此 API 允許將一組具有不同解析度的影像用作單個多解析度影像。

考慮以下影像。

這些是三個不同大小的徽標影像。

現在，為了使用這三個影像，從 Java 9 開始，可以使用多解析度影像 API 作為單個 API 來獲取所有變體或要顯示的特定變體。

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

這裡 MultiResolutionImage 和 BaseMultiResolutionImage 類是 java.awt.image 包的一部分。

以下是多解析度影像的主要操作。

• Image getResolutionVariant(double destImageWidth, double destImageHeight) − 獲取最適合在指示大小下表示此邏輯影像的特定影像。

• List<Image> getResolutionVariants() − 獲取所有解析度變體的可讀列表。

示例 - 獲取所有變體

在此示例中，我們載入了三個影像並將它們儲存在 MultiResolutionImage 中。然後使用 getResolutionVariants() 方法，我們檢查此多解析度影像中所有可用的影像變體並列印它。

package com.tutorialspoint;

import java.awt.Image;
import java.awt.image.BaseMultiResolutionImage;
import java.awt.image.MultiResolutionImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import javax.imageio.ImageIO;

public class Tester {
   public static void main(String[] args) throws IOException, MalformedURLException {

	  // prepare a list of urls of all images
      List<String> imgUrls = List.of("https://tutorialspoint.tw/java9/images/logo.png",
         "https://tutorialspoint.tw/java9/images/mini_logo.png",
         "https://tutorialspoint.tw/java9/images/large_logo.png");

      // create a list of Image object
      List<Image> images = new ArrayList<Image>();

      // Create image objects using image urls
      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());
     
      // print all the images
      for (Image img : variants) {
         System.out.println(img);
      }     
   }  
}

輸出

讓我們編譯並執行上述程式，這將產生以下結果：

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

示例 - 獲取特定變體

在此示例中，我們載入了三個影像並將它們儲存在 MultiResolutionImage 中。然後使用 getResolutionVariant() 方法，我們根據此多解析度影像中提供的解析度獲取特定影像變體並列印它。如果解析度不完全匹配，此方法將返回最接近的解析度影像。

package com.tutorialspoint;

import java.awt.Image;
import java.awt.image.BaseMultiResolutionImage;
import java.awt.image.MultiResolutionImage;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import javax.imageio.ImageIO;

public class Tester {
   public static void main(String[] args) throws IOException, MalformedURLException {

	  // prepare a list of urls of all images
      List<String> imgUrls = List.of("https://tutorialspoint.tw/java9/images/logo.png",
         "https://tutorialspoint.tw/java9/images/mini_logo.png",
         "https://tutorialspoint.tw/java9/images/large_logo.png");

      // create a list of Image object
      List<Image> images = new ArrayList<Image>();

      // Create image objects using image urls
      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());
     
      // 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));
   }  
} 

輸出

讓我們編譯並執行上述程式，這將產生以下結果：

Total number of images: 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]