java IMAGEIO

javax.imageio
使用 ImageIO 类的静态方法可以执行许多常见的图像 I/O 操作。 　　
此包包含一些基本类和接口，有的用来描述图像文件内容（包括元数据和缩略图）(IIOImage)；

有的用来控制图像读取过程（ImageReader、ImageReadParam）和控制图像写入过程（ImageWriter 和 ImageWriteParam）；

详细 Java ImageIO处理图像的封装例子     http://www.gzhost.net/Artdetail-1609-649.html

package com.mapbar.graphics;

import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.Iterator;

import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageReader;
import javax.imageio.metadata.IIOMetadata;
import javax.imageio.stream.ImageInputStream;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**
 *
 * Class ImageIOTest.java
 *
 * Description javax.imageio 操作
 *
 * Company mapbar
 *
 * author Chenll E-mail: Chenll@mapbar.com
 *
 * Version 1.0
 *
 * Date 2012-7-23 上午11:16:17
 */
public class ImageIOTest {

    /**
     * Java Image I/O API 支持的读入，写出普通的格式，如果需要开发其它格式，还需要第三方插件，eg JIMI, JMagic
     */
    public void formatImageNames() {

        String[] imageFormats = ImageIO.getReaderFormatNames();
        // [jpg, BMP, bmp, JPG, wbmp, jpeg, png, PNG, JPEG, WBMP, GIF, gif]
        System.out.println(Arrays.asList(imageFormats));

        String[] imageFormats1 = ImageIO.getWriterFormatNames();
        // [BMP, bmp, jpg, JPG, wbmp, jpeg, png, PNG, JPEG, WBMP, GIF, gif]
        System.out.println(Arrays.asList(imageFormats1));

    }

    /**
     * Image I/O高级操作 ImageReader ImageWriter 通过ImageReader
     * 可以获取图片信息而不用把整张图片数据都读入内存。
     *
     * @throws IOException
     */
    public void imageReaderOp() throws IOException {
        Iterator<ImageReader> readers = ImageIO
                .getImageReadersByFormatName("JPG");
        ImageReader reader = readers.next();
        // 构造输入源
        File bigFile = new File("E:\big.JPG");
        ImageInputStream iis = ImageIO.createImageInputStream(bigFile);
        // 输入源和ImageReader关联
        reader.setInput(iis, true);
        // 获取第一张图片的高度,试图解码文件的必要部分，去获取图片的宽度，而不用读取任何一个象素
        int imageIndex = 0;
        int width = reader.getWidth(imageIndex);
    }

    /**
     * 控制图片操作，ImageReadParam 可以让程序更好的控制内存，比如指定一个感兴趣的区域
     *
     * @throws IOException
     */
    public void imageReadParamOp() throws IOException {
        int imageIndex = 0;
        Iterator<ImageReader> readers = ImageIO
                .getImageReadersByFormatName("JPG");
        ImageReader reader = readers.next();
        File bigFile = new File("E:\big.JPG");
        ImageInputStream iis = ImageIO.createImageInputStream(bigFile);
        reader.setInput(iis, true);
        ImageReadParam irp = reader.getDefaultReadParam();
        int halfWidth = reader.getWidth(imageIndex) / 2;
        int halfHeight = reader.getHeight(imageIndex) / 2;
        Rectangle rect = new Rectangle(0, 0, halfWidth, halfHeight);
        irp.setSourceRegion(rect);
        BufferedImage bi = reader.read(imageIndex, irp);
        ImageIO.write(bi, "JPG", new File("E:\big_half.JPG"));
    }

    /**
     * 图片元信息
     *
     * @throws IOException
     */
    public void ImageMetadata() throws IOException {
        int imageIndex = 0;
        Iterator<ImageReader> readers = ImageIO
                .getImageReadersByFormatName("JPG");
        ImageReader reader = readers.next();
        File bigFile = new File("E:\big.JPG");
        ImageInputStream iis = ImageIO.createImageInputStream(bigFile);
        reader.setInput(iis, true);
        IIOMetadata metadata = reader.getImageMetadata(imageIndex);
    }

    /**
     * 生成缩略图
     *
     * @throws IOException
     */
    public void generateSmall() throws IOException {
        File bigFile = new File("E:\big.JPG");
        Image image = ImageIO.read(bigFile);
        int width = image.getWidth(null); // 3264
        int height = image.getHeight(null); // 2448
        BufferedImage buffi = new BufferedImage(width / 2, height / 2,
                BufferedImage.TYPE_INT_RGB);
        Graphics g = buffi.getGraphics();
        g.drawImage(image, 0, 0, width / 2, height / 2, null);
        g.dispose();
        ImageIO.write(buffi, "JPG", new File("E:\small.JPG"));// 1632 height:1224
    }

    public static void main(String[] args) throws IOException {
        ImageIOTest iot = new ImageIOTest();
        iot.generateSmall();
        iot.formatImageNames();
        iot.imageReaderOp();
        iot.imageReadParamOp();
        iot.ImageMetadata();
    }

}