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();
                }
        }