JAVA切图 等比例缩放

import java.awt.Image;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import javax.imageio.stream.MemoryCacheImageInputStream;

/**
 * 图片工具类
 * 
 * @author Administrator
 * 
 */
public final class ImageUtils {

	public static final String PNG = "png";
	public static final String JPG = "jpg";
	public static final String BMP = "bmp";
	public static final String GIF = "gif";

	public static void main(String[] args) {
		zoom("D:\\1.jpg", "D:\\2.jpg", 365, "jpg");
	}

	/**
	 * 缩放图片
	 * 
	 * @param picFrom
	 *            源图片地址
	 * @param picTo
	 *            目标图片地址
	 * @param size
	 *            目标图片宽度
	 * @param formart
	 *            目标图片格式
	 * @return
	 */
	public static String zoom(String picFrom, String picTo, int size,
			String formart) {
		formart = JPG;
		try {
			byte[] k1 = readFromFile(picFrom);
			BufferedImage img = getScaleImage(k1, formart.toUpperCase(), size);
			RenderedImage rendImage = getScaleImage(k1, formart.toUpperCase(),
					size);
			// 以下是将图形保存为标准图片格式
			ImageIO.write(rendImage, formart.toUpperCase(), new File(picTo));
		} catch (IOException e) {

		}
		return picTo;
	}

	public static byte[] readFromFile(String path) throws IOException {
		InputStream is = new FileInputStream(new File(path));
		byte[] buf = new byte[is.available()];
		is.read(buf);
		is.close();
		return buf;
	}

	/**
	 * 构建一个image对象
	 * 
	 * @param img
	 * @return
	 * @throws IOException
	 */
	public static ImageInfo getImageInfo(byte[] img) throws IOException {
		ByteArrayInputStream bais = new ByteArrayInputStream(img);
		MemoryCacheImageInputStream is = new MemoryCacheImageInputStream(bais);
		Iterator<ImageReader> it = ImageIO.getImageReaders(is);
		ImageReader r = null;
		while (it.hasNext()) {
			r = it.next();
			break;
		}
		if (r == null) {
			return null;
		}
		ImageInfo i = new ImageInfo();
		i.setType(r.getFormatName().toLowerCase());
		int index = r.getMinIndex();
		/**
		 * 对于ImageReader的线程安全是不确定的
		 */
		synchronized (r) {
			r.setInput(is);
			i.setHeight(r.getHeight(index));
			i.setWidth(r.getWidth(index));
		}
		return i;
	}

	public static BufferedImage getImage(byte[] img) throws IOException {
		ByteArrayInputStream bais = new ByteArrayInputStream(img);
		BufferedImage src = ImageIO.read(bais);
		return src;
	}

	/**
	 * 等比例缩放
	 * 
	 * @param img
	 * @param width
	 * @return
	 * @throws IOException
	 */
	public static BufferedImage getScaleImage(byte[] img, String type, int width)
			throws IOException {
		ByteArrayInputStream bais = new ByteArrayInputStream(img);
		BufferedImage src = ImageIO.read(bais);
		int w = src.getWidth();
		int h = src.getHeight();
		int height = (int) (((float) width / w) * h);
		Image im = src.getScaledInstance(width, height, Image.SCALE_SMOOTH);
		BufferedImage bi = new BufferedImage(width, height, src.getType());
		bi.getGraphics().drawImage(im, 0, 0, null);
		return bi;
	}

	public static byte[] getScaleImageBytes(byte[] img, String type, int width)
			throws IOException {
		BufferedImage bi = getScaleImage(img, type, width);
		ByteArrayOutputStream out = new ByteArrayOutputStream();
		ImageIO.write(bi, type, out);
		return out.toByteArray();
	}

	/**
	 * 获取文件类型,没找到返回null,这方法太高效了,可能不准确, 这个是我看的网上的，有bug不准确
	 * 
	 * @param byte1
	 * @return
	 */
	public static String fastParseFileType(byte[] byte1) {
		if ((byte1[0] == 71) && (byte1[1] == 73) && (byte1[2] == 70)
				&& (byte1[3] == 56) && ((byte1[4] == 55) || (byte1[4] == 57))
				&& (byte1[5] == 97)) {
			return GIF;
		}
		if ((byte1[6] == 74) && (byte1[7] == 70) && (byte1[8] == 73)
				&& (byte1[9] == 70)) {
			return JPG;
		}
		if ((byte1[0] == 66) && (byte1[1] == 77)) {
			return BMP;
		}
		if ((byte1[1] == 80) && (byte1[2] == 78) && (byte1[3] == 71)) {
			return PNG;
		}
		return null;
	}

	public static class ImageInfo {
		private String type;
		private int width;
		private int height;

		public String getType() {
			return type;
		}

		public void setType(String type) {
			this.type = type;
		}

		public int getWidth() {
			return width;
		}

		public void setWidth(int width) {
			this.width = width;
		}

		public int getHeight() {
			return height;
		}

		public void setHeight(int height) {
			this.height = height;
		}
	}
}