对上传的图片进行等比例压缩

/**
	 * 修改系统Logo
	 * @param file
	 * @param systemBasicConfigurationDTO
	 */
	@PutMapping(value = "/updateSystemLogo")
	@ApiOperation(value = "修改系统Logo", notes = "修改系统Logo的接口")
	public R updateSystemLogo(MultipartFile file, SystemBasicConfigurationDTO systemBasicConfigurationDTO) {
		try {
			SystemBasicConfiguration systemBasicConfiguration = new SystemBasicConfiguration();
			BeanUtils.copyProperties(systemBasicConfigurationDTO, systemBasicConfiguration);
			String systemConfigurationKey = systemBasicConfiguration.getConfigKey();
			InputStream input = file.getInputStream();
			Long imgaeSize = file.getSize();
			if (imgaeSize > 4 * 1024 * 1024) {
				return R.error().msg("图片超过4M大小");
			}
			//按比例压缩图片
			InputStream result = reduceImg(input, "upload.png", 0.5);
			SystemBasicConfiguration sbc = new SystemBasicConfiguration();
			sbc.setConfigKey(systemConfigurationKey);
			EntityWrapper wrapper = new EntityWrapper<>();
			wrapper.setEntity(sbc);
			systemBasicConfiguration.setConfigValue(Image2Base64Utils.imgFileToBase64(result));
			systemBasicConfigurationService.update(systemBasicConfiguration, wrapper);
			return R.ok().data("成功修改系统Logo");
		} catch (Exception e) {
			return R.error().msg(e.getMessage());
		}
	}







/**
	 * @description 按比例压缩图片
	 * @param is    源图片流
	 * @param imgdist 图片名字
	 * @param rate     压缩比例
	 * @return
	 */
	public static InputStream reduceImg(InputStream is, String imgdist, Double rate) {
		try {
			int widthdist = 0;
			int heightdist = 0;
			BufferedImage sourceImg = ImageIO.read(is);
			widthdist = (int) (sourceImg.getWidth() * rate);
			heightdist = (int) (sourceImg.getHeight() * rate);
			// 开始读取文件并进行压缩
			BufferedImage tag = new BufferedImage((int) widthdist, (int) heightdist, BufferedImage.TYPE_INT_RGB);
			tag.getGraphics()
					.drawImage(sourceImg.getScaledInstance(widthdist, heightdist, Image.SCALE_SMOOTH), 0, 0, null);
			FileOutputStream out = new FileOutputStream(imgdist);
			JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
			encoder.encode(tag);
			out.close();
			File srcfile = new File(imgdist);
			InputStream result = new FileInputStream(srcfile);
			return result;
		} catch (IOException ex) {
			ex.printStackTrace();
		}
		return null;
	}