java图片压缩

1、首先从Fast服务器获取图片流，然后将流转化成BufferedImage

2、从BufferedImage根据需要的宽度和高度获取压缩图片实例

3、对压缩图片实例进行重绘，将图片绘制到BufferedImage

4、使用ImageIO对BufferedImage进行流读写的操作，输出到本地磁盘系统或上传到fast服务器

public class FileUtilsFastDfsAdapter{
    @Resource
    private FastDfsUtils fastDfsUtils;

    @Value("${fastdfs.fileServer}")
    private String fastUrl;

/**
*按照指定宽度进行压缩
*
*/
 public String getScaleImage(String url, Integer width, Integer height) throws IOException, MyException {
        byte[] fileByte = fastDfsUtils.getFileByte(url);
        BufferedImageVo bufferedImageVo = getBufferedImage(fileByte);
        BufferedImage bufferedImage = bufferedImageVo.getBufferedImage();
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        String jpgId = getUrl(bufferedImageVo, bufferedImage, (int) height, (int) width);
        return jpgId;
    }
    
private BufferedImageVo getBufferedImage(byte[] fileByte) throws IOException {
        BufferedImageVo bufferedImageVo = new BufferedImageVo();

        // 将字节数组转为InputStream，再转为MemoryCacheImageInputStream
        ImageInputStream imageInputstream = new MemoryCacheImageInputStream(new ByteArrayInputStream(fileByte));
        // 获取所有能识别数据流格式的ImageReader对象
        Iterator<ImageReader> it = ImageIO.getImageReaders(imageInputstream);
        BufferedImage bufferedImage= null;
        int originalWidth = 0,originalHeight = 0;
        // 迭代器遍历尝试用ImageReader对象进行解码
        while (it.hasNext()) {
            ImageReader imageReader = it.next();
            // 设置解码器的输入流
            imageReader.setInput(imageInputstream, true, true);
            // 图像文件格式后缀
            String suffix = imageReader.getFormatName().trim().toLowerCase();
            // 图像宽度
            originalWidth = imageReader.getWidth(0);
            // 图像高度
            originalHeight = imageReader.getHeight(0);
            System.out.printf("format %s,%dx%d
", suffix, originalWidth, originalHeight);
            try {
                // 解码成功返回BufferedImage对象
                // 0即为对第0张图像解码(gif格式会有多张图像),前面获取宽度高度的方法中的参数0也是同样的意思
                bufferedImage = imageReader.read(0, imageReader.getDefaultReadParam());
            } catch (Exception e) {
                imageReader.dispose();
                // 如果解码失败尝试用下一个ImageReader解码
            }
            bufferedImageVo.setSuffix(suffix);
        }
        bufferedImageVo.setBufferedImage(bufferedImage);

        return bufferedImageVo;
    }

/**
*根据提供的最大边进行等比例压缩
*
*/
public String getScaleImage(String url, Integer maxLength) throws IOException, MyException {
        byte[] fileByte = fastDfsUtils.getFileByte(url);
        BufferedImageVo bufferedImageVo = getBufferedImage(fileByte);
        BufferedImage bufferedImage = bufferedImageVo.getBufferedImage();
        // 图像宽度
        int originalWidth = bufferedImage.getWidth();
        // 图像高度
        int originalHeight = bufferedImage.getHeight();
        //按压缩压缩比例获取宽度和高度
        Float bl;
        if(originalHeight>originalWidth){
            bl = maxLength/Convert.toFloat(originalHeight);
        }else{
            bl = maxLength/Convert.toFloat(originalWidth);
        }
        float height = originalHeight * bl;
        float width = originalWidth * bl;
        String jpgId = getUrl(bufferedImageVo, bufferedImage, (int) height, (int) width);
        return jpgId;
    }

/**
     * 对图像进行压缩并上传到fast
     * @param bufferedImageVo 提供图片后缀
     * @param bufferedImage 原图片buffered,提供压缩模板
     * @param height    压缩后的高度
     * @param width     压缩后的宽度
     * @return
     * @throws IOException
     * @throws MyException
     */
    private String getUrl(BufferedImageVo bufferedImageVo, BufferedImage bufferedImage, int height, int width) throws IOException, MyException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
　　　　　//获取压缩图片实例
        Image scaledInstance = bufferedImage.getScaledInstance(width, height, Image.SCALE_SMOOTH);
        BufferedImage outImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics graphics = outImage.getGraphics();
　　　　 //进行重绘
        graphics.drawImage(scaledInstance,0,0,null);
        graphics.dispose();
        bufferedImage.getType();
        ImageIO.write(outImage,bufferedImageVo.getSuffix(),bos);
        outImage.flush();
        return fastDfsUtils.upload(bos.toByteArray(), bufferedImageVo.getSuffix());
    }
}