绘制多边形

#java.awt绘制多边形

核心API

drawPolygon(int xPoints[], int yPoints[], int nPoints) 

示例

	/**
	 * 根据图像Base64字符串、摄像机id、算法id画多边形（支持同一画面画多个多边形）
	 * @param base64 图像base64字符串
	 * @param cameraId 坐标json字符传  已绘制的坐标框坐标信息
	 * 坐标如 [{"x":800,"y":600},{"x":1000,"y":850},{"x":950"y":1050},{"x":850,"y":1200},{"x":820,"y":600}]
	 * @param algId 算法id
	 * @return 图像Base64字符串
	 */
public static String drawPolygon(String cameraId,String base64,String algId){
		LambdaQueryWrapper<CameraAlgorithmRelation> queryWrapper = new LambdaQueryWrapper();
		queryWrapper.eq(CameraAlgorithmRelation::getCameraId,cameraId)
            .eq(CameraAlgorithmRelation::getAlgorithmInfoId,algId);
		CameraAlgorithmRelation relation = cameraAlgorithmRelationMapper.selectOne(queryWrapper);
		if (!Objects.isNull(relation)){
			String points = relation.getAlgArea();
			List<List<PointDTO>> pointList = new ArrayList<>();
			if (StringUtils.isNotEmpty(points)){
				pointList = JSON.parseObject(points,List.class);
				byte[] byteArray = Base64.decode(base64);
				String fileSuffix = getImageBase64Format(byteArray);
				if (StringUtils.isEmpty(fileSuffix)) {
					throw new BusinessException("获取文件格式异常");
				}
				BufferedImage bufferedImage = null;
				ByteArrayInputStream inputStream = new ByteArrayInputStream(byteArray);
				try {
					bufferedImage = ImageIO.read(inputStream);
				} catch (IOException e) {
					log.error("读取图片异常：.......{}",e.getLocalizedMessage());
					e.printStackTrace();
				}
				Graphics2D graphics2D = bufferedImage.createGraphics();
				for (List<PointDTO> pointDTOList : pointList) {
					JSONArray array = JSONObject.parseArray(JSON.toJSONString(pointDTOList));
					List<PointDTO> pointDTOS = array.toJavaList(PointDTO.class);
					List<Integer> xList = pointDTOS.stream().map(PointDTO::getX).collect(Collectors.toList());
					List<Integer> yList = pointDTOS.stream().map(PointDTO::getY).collect(Collectors.toList());
					int[] x = xList.stream().mapToInt(Integer::valueOf).toArray();
					int[] y = yList.stream().mapToInt(Integer::valueOf).toArray();
					graphics2D.setColor(Color.GREEN);
					graphics2D.drawPolygon(x, y, pointDTOS.size());
				}
				return bufferImageToBase64(bufferedImage);
			}
		}
		return null;
	}

/**
* 验证图片格式
* @param path
* @return java.lang.String
*/
private static String getImageBase64Format(byte[] b) {
		String type = "";
		int temp = (b[0] & 255) << 8 | b[1] & 255;
		if (16973 == temp) {
			type = "bmp";
		} else if (35152 == temp) {
			type = "png";
		} else if (65496 == temp) {
			type = "jpg";
		} else if (18249 == temp) {
			type = "gif";
		} else if (21065 == temp) {
			type = "webp";
		}
		return type;
	}

	/**
	 * 图片路径读取转Base64字符串
	 * @param path
	 * @return java.lang.String
	 */
public static String convertBase64(String path){
		String base64 = "";
		try {
			URL url = ResourceUtil.getResource(path);
			BufferedImage bufferedImage = cn.hutool.core.img.ImgUtil.read(url);
			ByteArrayOutputStream stream = new ByteArrayOutputStream();
			ImageIO.write(bufferedImage,"jpg",stream);
			base64 = Base64.encode(stream.toByteArray());
		} catch (IOException e){
			throw new RuntimeException("图片转换Base64失败");
		}
		return base64;
	}

	/**
	 * BufferedImage转Base64字符串
	 * @param bufferedImage
	 * @return java.lang.String
	 */
	public static String bufferImageToBase64(BufferedImage bufferedImage) {
		ByteArrayOutputStream stream = new ByteArrayOutputStream();
		try {
			ImageIO.write(bufferedImage,"jpg",stream);
		} catch (IOException e) {
			log.error("BufferedImage转Base64字符串失败",e.getLocalizedMessage());
		}
		return Base64.encode(stream.toByteArray());
	}