java生成高质量缩略图的代码实现详解编程语言

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; 
 
/** *//** 
 * @将文件转化为缩略图 
 * 
 */ 
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); // 读取14字节BMP文件头 
            int biLen = 40; 
            byte bi[] = new byte[biLen]; 
            fs.read(bi, 0, biLen); // 读取40字节BMP信息头 
 
            // 源图宽度 
            int nWidth = (((int) bi[7] & 0xff) << 24) 
                    | (((int) bi[6] & 0xff) << 16) 
                    | (((int) bi[5] & 0xff) << 8) | (int) bi[4] & 0xff; 
 
            // 源图高度 
            int nHeight = (((int) bi[11] & 0xff) << 24) 
                    | (((int) bi[10] & 0xff) << 16) 
                    | (((int) bi[9] & 0xff) << 8) | (int) bi[8] & 0xff; 
 
            // 位数 
            int nBitCount = (((int) bi[15] & 0xff) << 8) | (int) bi[14] & 0xff; 
 
            // 源图大小 
            int nSizeImage = (((int) bi[23] & 0xff) << 24) 
                    | (((int) bi[22] & 0xff) << 16) 
                    | (((int) bi[21] & 0xff) << 8) | (int) bi[20] & 0xff; 
 
            // 对24位BMP进行解析 
            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); 
    } 
 
}