java生成高質量縮略圖的代碼實現

import java.awt.Image;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.awt.image.MemoryImageSource;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

import javax.imageio.ImageIO;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
/ *//

@將文件轉化為縮略圖
/
public class jpgThumbnail {
private static final String BMP = "bmp";
 private static final String PNG = "png";
 private static final String GIF = "gif";
 private static final String JPEG = "jpeg";
 private static final String JPG = "jpg";
public static void getThumbnail(

     String source,
     String output,
     int width,
     int height) {
 boolean adjustSize=true;
 if (source == null || source.equals("") || width < 1 || height < 1) {
     return;
 }
 if(output==null || output.equals(""))
 {
     return;
 }
 source = source.toLowerCase();
 if (source.endsWith(BMP)) {
     BMPThumbnailHandler(source, output,width, height, adjustSize);
 } else if (source.endsWith(PNG) || source.endsWith(GIF)
         || source.endsWith(JPEG) || source.endsWith(JPG)) {
     thumbnailHandler(source, output,width, height, adjustSize);
 }

}
private static void thumbnailHandler(

     String source,
     String output,
     int width,
     int height,
     boolean adjustSize) {
 try {
     File sourceFile = new File(source);
     if (sourceFile.exists()) {
         Image image = ImageIO.read(sourceFile);
         int theImgWidth = image.getWidth(null);
         int theImgHeight = image.getHeight(null);
         int[] size = { theImgWidth, theImgHeight };
         if (adjustSize) {
             size = adjustImageSize(theImgWidth, theImgHeight, width,height);
         }
         StringBuffer thumbnailFile=new StringBuffer();
         //thumbnailFile.append(sourceFile.getParent());
         //thumbnailFile.append(File.separatorChar);
         thumbnailFile.append(output);
         writeFile(image, size[0], size[1], thumbnailFile.toString());
     }
 } catch (Exception e) {
     e.printStackTrace();
     return;
 }

}
private static void BMPThumbnailHandler(

     String source,
     String output,
     int width,
     int height,
     boolean adjustSize) {
 try {
     File sourceFile = new File(source);
     if (sourceFile.exists()) {
         Image image = getBMPImage(source);
         int theImgWidth = image.getWidth(null);
         int theImgHeight = image.getHeight(null);
         int[] size = { theImgWidth, theImgHeight };
         if (adjustSize) {
             size = adjustImageSize(theImgWidth, theImgHeight, width, height);
         }
         StringBuffer thumbnailFile=new StringBuffer();
         //thumbnailFile.append(sourceFile.getParent());
         //thumbnailFile.append(File.separatorChar);
         thumbnailFile.append(output);
         writeFile(image, size[0], size[1], thumbnailFile.toString());
     }
 } catch (Exception e) {
     e.printStackTrace();
     return;
 }

}
private static Image getBMPImage(String source) throws Exception {

 FileInputStream fs = null;
 Image image = null;
 try {
     fs = new FileInputStream(source);
     int bfLen = 14;
     byte bf[] = new byte[bfLen];
     fs.read(bf, 0, bfLen); // 讀取14字節BMP文件頭
     int biLen = 40;
     byte bi[] = new byte[biLen];
     fs.read(bi, 0, biLen); // 讀取40字節BMP信息頭

     // 源圖寬度
     int nWidth = (((int) bi[7] & 0xff) << 24)
             | (((int) bi[6] & 0xff) << 16)
             | (((int) bi[5] & 0xff) << 8) | (int) bi[4] & 0xff;

     // 源圖高度
     int nHeight = (((int) bi[11] & 0xff) << 24)
             | (((int) bi[10] & 0xff) << 16)
             | (((int) bi[9] & 0xff) << 8) | (int) bi[8] & 0xff;

     // 位數
     int nBitCount = (((int) bi[15] & 0xff) << 8) | (int) bi[14] & 0xff;

     // 源圖大小
     int nSizeImage = (((int) bi[23] & 0xff) << 24)
             | (((int) bi[22] & 0xff) << 16)
             | (((int) bi[21] & 0xff) << 8) | (int) bi[20] & 0xff;

     // 對24位BMP進行解析
     if (nBitCount == 24) {
         int nPad = (nSizeImage / nHeight) - nWidth * 3;
         int nData[] = new int[nHeight * nWidth];
         byte bRGB[] = new byte[(nWidth + nPad) * 3 * nHeight];
         fs.read(bRGB, 0, (nWidth + nPad) * 3 * nHeight);
         int nIndex = 0;
         for (int j = 0; j < nHeight; j++) {
             for (int i = 0; i < nWidth; i++) {
                 nData[nWidth * (nHeight - j - 1) + i] = (255 & 0xff) << 24
                         | (((int) bRGB[nIndex + 2] & 0xff) << 16)
                         | (((int) bRGB[nIndex + 1] & 0xff) << 8)
                         | (int) bRGB[nIndex] & 0xff;
                 nIndex += 3;
             }
             nIndex += nPad;
         }
         Toolkit kit = Toolkit.getDefaultToolkit();
         image = kit.createImage(new MemoryImageSource(nWidth, nHeight,
                 nData, 0, nWidth));
     }
 } catch (Exception e) {
     e.printStackTrace();
     throw new Exception(e);
 } finally {
     if (fs != null) {
         fs.close();
     }
 }
 return image;

}
private static void writeFile(

     Image image,
     int width,
     int height,
     String thumbnailFile) throws Exception {

 if (image == null) return;

 BufferedImage tag = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
 tag.getGraphics().drawImage(image, 0, 0, width, height, null);
 FileOutputStream out = null;
 try {
     out = new FileOutputStream(thumbnailFile);
     JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
     encoder.encode(tag);
 } catch (Exception e) {
     e.printStackTrace();
     throw new Exception(e);
 } finally {
     if (out != null) {
         out.close();
     }
 }


}
private static int[] adjustImageSize(int theImgWidth, int theImgHeight,

     int defWidth, int defHeight) {        
 int[] size = { 0, 0 };

 float theImgHeightFloat=Float.parseFloat(String.valueOf(theImgHeight));
 float theImgWidthFloat=Float.parseFloat(String.valueOf(theImgWidth));
 if (theImgWidth<theImgHeight){
     float scale=theImgHeightFloat/theImgWidthFloat;
     size[0]=Math.round(defHeight/scale);
     size[1]=defHeight;
 }else{
     float scale=theImgWidthFloat/theImgHeightFloat;
     size[0]=defWidth;
     size[1]=Math.round(defWidth/scale);
 }
 return size;

}
public static void main(String[] agrs) {

 //zoomPicture("E:\\1.jpg","E:\\test.jpg",60, 80);
 getThumbnail("E:\\1.jpg","E:\\test.jpg",60, 80);

}


}</pre>