public class ImageToBase64 {

     //图片转化成base64字符串

    public static String GetImageStr(String path,int width,int height) throws IOException

    {//将图片文件转化为字节数组字符串，并对其进行Base64编码处理

        File srcFile = new File(path);//文件上服务器上面的地址

        if (!srcFile.exists())

            return "";

        Image srcImg = ImageIO.read(srcFile);

        // 生成指定大小图片

        BufferedImage buffImg = null;

        int oldWidth = srcImg.getWidth(null);

        int oldHeight = srcImg.getHeight(null);

        // 计算原图等比缩放长宽

        if (oldWidth * height > width * oldHeight) {

            oldHeight = width * oldHeight / oldWidth;

            oldWidth = width;

        } else {

            oldWidth = height * oldWidth / oldHeight;

            oldHeight = height;

        }

        // 生成新图

        buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        // 填白

        buffImg.getGraphics().fillRect(0, 0, width, height);

        // 填入原图

        buffImg.getGraphics().drawImage(srcImg.getScaledInstance(oldWidth, oldHeight, Image.SCALE_SMOOTH),

                (width - oldWidth) / 2, (height - oldHeight) / 2, null);

        ByteArrayOutputStream bs = new ByteArrayOutputStream();

        ImageOutputStream imOut = ImageIO.createImageOutputStream(bs);

        ImageIO.write(buffImg, "jpg", imOut);

        InputStream in = new ByteArrayInputStream(bs.toByteArray());

        byte[] data = null;

        //读取图片字节数组

        try

        {

            data = new byte[in.available()];

            in.read(data);

            in.close();

        }

        catch (IOException e)

        {

           return "";

        }

//        String fileName=srcFile.getName();

        //String prefix="data:image/jpg"+fileName.substring(fileName.lastIndexOf(".")+1)+";base64,";

        String prefix="data:image/jpg;base64,";

        return prefix+Base64.encodeBase64String(data);//返回Base64编码过的字节数组字符串

    }

}