java的圖像縮略方法

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原文链接：http://www.cnblogs.com/waya/archive/2008/11/04/1326402.html

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#java

java的圖像縮略方法

圖像的縮略代碼

                     // Image image = ImageIO.read(is);
                    Image src = Toolkit.getDefaultToolkit().getImage(file.getPath()); // 可讀取丟失ICC信息的圖片
                    BufferedImage image = BufferedImageBuilder.toBufferedImage(src); // Image to BufferedImage
                     int w = image.getWidth( null );
                     int h = image.getHeight( null );

                     // 縮略圖的size
                     int size = getFileSize(flag);
                     if (size == 0 )size = h;
                     int nw = size;
                     int nh = (nw * h) / w;
                     if (nh > size){
                        nh = size;
                        nw = (nh * w) / h;
                    }
                    BufferedImage tag = new BufferedImage(nw,nh,BufferedImage.TYPE_INT_RGB);
                    tag.getGraphics().drawImage(image.getScaledInstance(nw, nh, Image.SCALE_SMOOTH), 0 , 0 , null );
                    FileOutputStream out = new FileOutputStream(imageFile);
                    JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
                    encoder.encode(tag);
                    out.close();

以下是Image轉換BufferedImage代碼

public static BufferedImage toBufferedImage(Image image) {
         if (image instanceof BufferedImage) {
             return (BufferedImage)image;
        }

         // This code ensures that all the pixels in the image are loaded
        image = new ImageIcon(image).getImage();

         // Determine if the image has transparent pixels; for this method's
         // implementation, see e661 Determining If an Image Has Transparent Pixels
         // boolean hasAlpha = hasAlpha(image);

         // Create a buffered image with a format that's compatible with the screen
        BufferedImage bimage = null ;
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
         try {
             // Determine the type of transparency of the new buffered image
             int transparency = Transparency.OPAQUE;
            /* if (hasAlpha) {
                transparency = Transparency.BITMASK;
            } */

             // Create the buffered image
            GraphicsDevice gs = ge.getDefaultScreenDevice();
            GraphicsConfiguration gc = gs.getDefaultConfiguration();
            bimage = gc.createCompatibleImage(
                image.getWidth( null ), image.getHeight( null ), transparency);
        } catch (HeadlessException e) {
             // The system does not have a screen
        }

         if (bimage == null ) {
             // Create a buffered image using the default color model
             int type = BufferedImage.TYPE_INT_RGB;
             // int type = BufferedImage.TYPE_3BYTE_BGR; // by wang
             /* if (hasAlpha) {
                type = BufferedImage.TYPE_INT_ARGB;
            } */
            bimage = new BufferedImage(image.getWidth( null ), image.getHeight( null ), type);
        }

         // Copy image to buffered image
        Graphics g = bimage.createGraphics();

         // Paint the image onto the buffered image
        g.drawImage(image, 0 , 0 , null );
        g.dispose();

         return bimage;
    }

以上的方法可以生成品質較高無鋸齒的新圖像文件

還有以下方法生成縮略圖的，如果是圖像失真較大，圖形可以用以下方法

// BufferedImage src = ImageIO.read(is);
                    Image image = Toolkit.getDefaultToolkit().getImage(file.getPath()); // 用它可以讀取丟失ICC信息的圖片
                    BufferedImageBuilder bib = new BufferedImageBuilder();
                    BufferedImage src = BufferedImageBuilder.toBufferedImage(image);
                     // BufferedImage src=bib.bufferImage(image);
                     int w = src.getWidth();
                     int h = src.getHeight();
                     int size = getFileSize(flag);
                     if (size == 0 )size = h;
                     int nw = size;
                     int nh = (nw * h) / w;
                     if (nh > size){
                        nh = size;
                        nw = (nh * w) / h;
                    }

                     // 縮圖的比例
                     double sx = ( double )nw / w;
                     double sy = ( double )nh / h;
                    AffineTransform transform = new AffineTransform();
                    transform.setToScale(sx, sy);
                    AffineTransformOp ato = new AffineTransformOp(transform, null );
                     int type = src.getColorModel().getColorSpace().getType();
                     if (type == 5 ){
                         // type=BufferedImage.TYPE_3BYTE_BGR;
                        type = BufferedImage.TYPE_INT_RGB;
                    } else if (type == 6 ){
                        type = BufferedImage.TYPE_BYTE_GRAY;
                    }
                    BufferedImage tag = new BufferedImage(nw, nh,type);
                    ato.filter(src, tag);
                     if (isGray && type != 6 ){
                         // 生成灰色圖片
                        tag = getGrayImage(tag);
                    }
                    ImageIO.write(tag, " jpeg " , imageFile);
                    tag.flush();
                    src.flush();
                    is.close();

把圖片轉成灰度圖

private BufferedImage getGrayImage(BufferedImage image){
        BufferedImage dstimage = new BufferedImage(image.getWidth(),image.getHeight(),image.getType());
        Graphics2D g2 = dstimage.createGraphics();
        RenderingHints hints = g2.getRenderingHints();
        g2.dispose();
        g2 = null ;
        ColorSpace grayCS = ColorSpace.getInstance(ColorSpace.CS_GRAY);
        ColorConvertOp colorConvertOp = new ColorConvertOp(grayCS,hints);
        colorConvertOp.filter(image, dstimage);
         return dstimage;
    }