图片转换工具类-ImageUtils

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
 */
public final class ImageUtils {

 public static void main(String[] args) {
  zoom("C:\\Users\\Administrator\\Pictures\\test.jpg",
    "C:\\Users\\Administrator\\Pictures\\1.jpg", 100, "jpg");
 }

 public static String zoom(String picFrom, String picTo, int width,
   String formart) {
  formart = JPG;
  try {
   byte[] k1 = readFromFile(picFrom);
   BufferedImage img = getScaleImage(k1, formart.toUpperCase(), width);
   RenderedImage rendImage = getScaleImage(k1, formart.toUpperCase(),
     width);
   // 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 final String PNG = "png";
 public static final String JPG = "jpg";
 public static final String BMP = "bmp";
 public static final String GIF = "gif";

 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;
  }
 }
}