java处理图片按比例缩放功能

java中的图片按比例缩放功能

1. 按固定长宽进行缩放

    /*
 * 图片缩放,w，h为缩放的目标宽度和高度
 * src为源文件目录，dest为缩放后保存目录
 */
    public static void zoomImage(String src,String dest,int w,int h) throws Exception {
        
        double wr=0,hr=0;
        File srcFile = new File(src);
        File destFile = new File(dest);

        BufferedImage bufImg = ImageIO.read(srcFile); //读取图片
        Image Itemp = bufImg.getScaledInstance(w, h, bufImg.SCALE_SMOOTH);//设置缩放目标图片模板
        
        wr=w*1.0/bufImg.getWidth();     //获取缩放比例
        hr=h*1.0 / bufImg.getHeight();

        AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(wr, hr), null);
        Itemp = ato.filter(bufImg, null);
        try {
            ImageIO.write((BufferedImage) Itemp,dest.substring(dest.lastIndexOf(".")+1), destFile); //写入缩减后的图片
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

2. 按固定文件大小进行缩放

   
    /*
 * 图片按比率缩放
 * size为文件大小
 */
    public static void zoomImage(String src,String dest,Integer size) throws Exception {
        File srcFile = new File(src);
        File destFile = new File(dest);
        
        long fileSize = srcFile.length();
        if(fileSize < size * 1024)   //文件大于size k时，才进行缩放,注意：size以K为单位
            return;
        
        Double rate = (size * 1024 * 0.5) / fileSize; // 获取长宽缩放比例
        
        BufferedImage bufImg = ImageIO.read(srcFile);
        Image Itemp = bufImg.getScaledInstance(bufImg.getWidth(), bufImg.getHeight(), bufImg.SCALE_SMOOTH);
            
        AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(rate, rate), null);
        Itemp = ato.filter(bufImg, null);
        try {
            ImageIO.write((BufferedImage) Itemp,dest.substring(dest.lastIndexOf(".")+1), destFile);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }