在JAVA中调整图片大小

在JAVA中，当我们调整图片的大小或比例时，我们可以按照以下的步棸：

1. 通过调用的ImageIO类的read(File)方法 创建用于输入图片BufferedImage对象。
2. 按所需输出高度输出的BufferedImage 对象。
3. 从输出图片的BufferedImage对象获取一个Graphics2D对象。
4. 画出输入图片的BufferedImage对象到输出图片的Graphics2D对象。
5. 用ImageIO这个类，write(File)方法将图片保存到硬盘。

这是一个图片操作的工具类。他实现了两个用于调整图片大小的方法。

package net.codejava.graphic;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
/**
 * 操作图片的代码.
 */
public class ImageResizer {
 
    /**
     * Resizes an image to a absolute width and height (the image may not be
     * proportional)
     * @param inputImagePath Path of the original image
     * @param outputImagePath Path to save the resized image
     * @param scaledWidth absolute width in pixels
     * @param scaledHeight absolute height in pixels
     * @throws IOException
     */
    public static void resize(String inputImagePath,
            String outputImagePath, int scaledWidth, int scaledHeight)
            throws IOException {
        // reads input image
        File inputFile = new File(inputImagePath);
        BufferedImage inputImage = ImageIO.read(inputFile);
 
        // creates output image
        BufferedImage outputImage = new BufferedImage(scaledWidth,
                scaledHeight, inputImage.getType());
 
        // scales the input image to the output image
        Graphics2D g2d = outputImage.createGraphics();
        g2d.drawImage(inputImage, 0, 0, scaledWidth, scaledHeight, null);
        g2d.dispose();
 
        // extracts extension of output file
        String formatName = outputImagePath.substring(outputImagePath
                .lastIndexOf(".") + 1);
 
        // writes to output file
        ImageIO.write(outputImage, formatName, new File(outputImagePath));
    }
 
    /**
     * Resizes an image by a percentage of original size (proportional).
     * @param inputImagePath Path of the original image
     * @param outputImagePath Path to save the resized image
     * @param percent a double number specifies percentage of the output image
     * over the input image.
     * @throws IOException
     */
    public static void resize(String inputImagePath,
            String outputImagePath, double percent) throws IOException {
        File inputFile = new File(inputImagePath);
        BufferedImage inputImage = ImageIO.read(inputFile);
        int scaledWidth = (int) (inputImage.getWidth() * percent);
        int scaledHeight = (int) (inputImage.getHeight() * percent);
        resize(inputImagePath, outputImagePath, scaledWidth, scaledHeight);
    }
 
    /**
     * Test resizing images
     */
    public static void main(String[] args) {
        String inputImagePath = "D:/Photo/Puppy.jpg";
        String outputImagePath1 = "D:/Photo/Puppy_Fixed.jpg";
        String outputImagePath2 = "D:/Photo/Puppy_Smaller.jpg";
        String outputImagePath3 = "D:/Photo/Puppy_Bigger.jpg";
 
        try {
            // resize to a fixed width (not proportional)
            int scaledWidth = 1024;
            int scaledHeight = 768;
            ImageResizer.resize(inputImagePath, outputImagePath1, scaledWidth, scaledHeight);
 
            // resize smaller by 50%
            double percent = 0.5;
            ImageResizer.resize(inputImagePath, outputImagePath2, percent);
 
            // resize bigger by 50%
            percent = 1.5;
            ImageResizer.resize(inputImagePath, outputImagePath3, percent);
 
        } catch (IOException ex) {
            System.out.println("Error resizing the image.");
            ex.printStackTrace();
        }
    }
 
}

[warning] 注意 这样操作图片可能会影响图片的质量[/warning]