java改变图片的大小

/**

* 改变图片的大小到宽为size，然后高随着宽等比例变化

* @param is 上传的图片的输入流

* @param os 改变了图片的大小后，把图片的流输出到目标OutputStream

* @param size 新图片的宽

* @param format 新图片的格式

* @throws IOException

*/ 

public staticvoid resizeImage(InputStream is, OutputStream os,int size, String format) throws IOException { 

    BufferedImage prevImage = ImageIO.read(is); 

    double width = prevImage.getWidth(); 

    double height = prevImage.getHeight(); 

    double percent = size/width; 

    int newWidth = (int)(width * percent); 

    int newHeight = (int)(height * percent); 

    BufferedImage image = new BufferedImage(newWidth, newHeight, BufferedImage.TYPE_INT_BGR); 

    Graphics graphics = image.createGraphics(); 

    graphics.drawImage(prevImage, 0, 0, newWidth, newHeight, null); 

    ImageIO.write(image, format, os); 

    os.flush(); 

    is.close(); 

    os.close(); 

}