Java 通过 base64 判断图片格式

Java 通过 base64 判断图片格式

    // base64字符串转写为文件
    public static void convertBase64DataToImage(String base64ImgData, String filePath) throws IOException {
        Files.write(Paths.get(filePath), Base64.getDecoder().decode(base64ImgData), StandardOpenOption.CREATE);
    }

    // 将文件转写为base64字符串
    public static String convertImageToBase64Data(String filePath) throws IOException {
        byte[] b = Files.readAllBytes(Paths.get(filePath));
        return Base64.getEncoder().encodeToString(b);
    }

    //判断图片base64字符串的文件格式
    public static String checkImageBase64Format(String base64ImgData) {
        byte[] b = Base64.getDecoder().decode(base64ImgData);
        String type = "";
        if (0x424D == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
            type = "bmp";
        } else if (0x8950 == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
            type = "png";
        } else if (0xFFD8 == ((b[0] & 0xff) << 8 | (b[1] & 0xff))) {
            type = "jpg";
        }
        return type;
    }


    public static String checkImageType(String base64Image) {
        // 将Base64字符串解码为字节数组
        byte[] imageBytes = Base64.getDecoder().decode(base64Image);

        // 检查JPEG格式
        if (imageBytes.length >= 2 && imageBytes[0] == (byte) 0xFF && imageBytes[1] == (byte) 0xD8) {
            return "JPEG";
        }

        // 检查PNG格式
        if (imageBytes.length >= 8 &&
                imageBytes[0] == (byte) 0x89 && imageBytes[1] == (byte) 0x50 &&
                imageBytes[2] == (byte) 0x4E && imageBytes[3] == (byte) 0x47 &&
                imageBytes[4] == (byte) 0x0D && imageBytes[5] == (byte) 0x0A &&
                imageBytes[6] == (byte) 0x1A && imageBytes[7] == (byte) 0x0A) {
            return "PNG";
        }

        // 检查GIF格式
        if (imageBytes.length >= 4 &&
                imageBytes[0] == (byte) 0x47 && imageBytes[1] == (byte) 0x49 &&
                imageBytes[2] == (byte) 0x46 && imageBytes[3] == (byte) 0x38) {
            return "GIF";
        }

        // 未知格式
        return "Unknown";
    }


    public static void main(String[] args) {
        File file = urlToFile("https://prod-read.oss-cn-shanghai.aliyuncs.com/img/2024-08-01/1722504255159.png");
        String base64 = null;
        InputStream in = null;

        try {
            in = new FileInputStream(file);
            byte[] bytes = new byte[(int) file.length()];
            in.read(bytes);
            base64 = new String(org.apache.commons.codec.binary.Base64.encodeBase64(bytes),"UTF-8");
            System.out.println("将文件[]转base64字符串:"+ base64);
            String s = checkImageType(base64);
            System.out.println("文件类型：" + s);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

作者：肃清万里，总齐八荒