Java高质量图片压缩

一、
**
     * 按指定高度 等比例缩放图片
     * 
     * @param imageFile
     * @param newPath
     * @param newWidth 新图的宽度
     * @throws IOException
     */
    public static void zoomImageScale(File imageFile, String newPath, int newWidth) throws IOException {
         if(!imageFile.canRead())
             return;
        BufferedImage bufferedImage = ImageIO.read(imageFile);
        if (null == bufferedImage) 
            return;
        
        int originalWidth = bufferedImage.getWidth();
        int originalHeight = bufferedImage.getHeight();
        double scale = (double)originalWidth / (double)newWidth;    // 缩放的比例
        
        int newHeight =  (int)(originalHeight / scale);

        zoomImageUtils(imageFile, newPath, bufferedImage, newWidth, newHeight);
    }
二、
private static void zoomImageUtils(File imageFile, String newPath, BufferedImage bufferedImage, int width, int height)
            throws IOException{
        
         String suffix = StringUtils.substringAfterLast(imageFile.getName(), ".");
        
         // 处理 png 背景变黑的问题
        if(suffix != null && (suffix.trim().toLowerCase().endsWith("png") || suffix.trim().toLowerCase().endsWith("gif"))){
            BufferedImage to= new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 
            Graphics2D g2d = to.createGraphics(); 
            to = g2d.getDeviceConfiguration().createCompatibleImage(width, height, Transparency.TRANSLUCENT); 
            g2d.dispose(); 
            
            g2d = to.createGraphics(); 
            Image from = bufferedImage.getScaledInstance(width, height, Image.SCALE_AREA_AVERAGING); 
            g2d.drawImage(from, 0, 0, null);
            g2d.dispose(); 
            
            ImageIO.write(to, suffix, new File(newPath));
        }else{
            BufferedImage newImage = new BufferedImage(width, height, bufferedImage.getType());
            Graphics g = newImage.getGraphics();
            g.drawImage(bufferedImage, 0, 0, width, height, null);
            g.dispose();
            ImageIO.write(newImage, suffix, new File(newPath));
        }
    }