Java 简明教程

Java - Multiresolution Image API

多分辨率图像 API 在 Java 9 中引入。该 API 支持具有不同分辨率变体的多个图像。该 API 允许将一组具有不同分辨率的图像用作单个多分辨率图像。

Multi-resolution image API was introduced in Java 9. This API supports multiple images with different resolution variants. This API allows a set of images with different resolution to be used as a single multi-resolution image.

考虑以下图像。

Consider the following images.

这些是具有不同大小的三张徽标图像。

These are three images of a logo with different sizes.

现在为了操作这三个图像，可以使用 Java 9 开始的多分辨率图像 API 作为单个 API，以获取所有变体或待显示的特定变体。

Now in order to work with these three images, Java 9 onwards, Multi-resolution Image API can be used as single API to get all variants or a particular variant to be displayed.

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

这里 MultiResolutionImage 和 BaseMultiResolutionImage 类是 java.awt.image 包的一部分。

Here MultiResolutionImage and BaseMultiResolutionImage classes are part of java.awt.image package.

以下是多分辨率图像的主要操作。

Following are major operations of multi-resolution image.

  1. Image getResolutionVariant(double destImageWidth, double destImageHeight) − Gets a specific image which is best variant to represent this logical image at the indicated size.

  2. List<Image> getResolutionVariants() − Gets a readable list of all resolution variants.

Example - Get All variants

在该示例中，我们加载了三个图像并将它们存储在 MultiResolutionImage 中。然后使用 getResolutionVariants() 方法，正在检查这个多分辨率图像中的所有可用图像变体并打印它。

In this example, we’ve loaded three images and store them in MultiResolutionImage. Then using getResolutionVariants() method, we’re checking all the available image variants in this multi-resolution image and printing it.

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("http://www.tutorialspoint.com/java9/images/logo.png",
         "http://www.tutorialspoint.com/java9/images/mini_logo.png",
         "http://www.tutorialspoint.com/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);
      }
   }
}

Output

让我们编译并运行上述程序，这将生成以下结果 −

Let us compile and run the above program, this will produce the following result −

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

Example - Get Specific variant

在这个示例中，我们加载了三张图像，并将它们存储在 MultiResolutionImage 中。然后，使用 getResolutionVariant() 方法，我们根据此多分辨率图像中提供的分辨率获取特定图像变体并将其打印出来。如果分辨率不完全匹配，此方法将返回最近 t 分辨率图像。

In this example, we’ve loaded three images and store them in MultiResolutionImage. Then using getResolutionVariant() method, we’re getting specific image variant as per the provided resolution in this multi-resolution image and printing it. In case resoltution is not exact match, this method returns the neares t resolution image.

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("http://www.tutorialspoint.com/java9/images/logo.png",
         "http://www.tutorialspoint.com/java9/images/mini_logo.png",
         "http://www.tutorialspoint.com/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));
   }
}

Output

让我们编译并运行上述程序，这将生成以下结果 −

Let us compile and run the above program, this will produce the following result −

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]