feat(基础功能增强):

新增两个base64工具：
1、检查base64字符串是否是图片
2、将网络图片转换为Base64字符串

ruoyi-common/ruoyi-common-core/src/main/java/com/ruoyi/common/core/utils/sign/Base64.java

@@ -1,5 +1,17 @@
 package com.ruoyi.common.core.utils.sign;
 
+import com.ruoyi.common.core.exception.ServiceException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import javax.imageio.ImageIO;
+import java.awt.image.BufferedImage;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+
 /**
  * Base64工具类
  * 
@@ -7,6 +19,7 @@ package com.ruoyi.common.core.utils.sign;
  */
 public final class Base64
 {
+    private static final Logger logger = LoggerFactory.getLogger(Base64.class);
     static private final int     BASELENGTH           = 128;
     static private final int     LOOKUPLENGTH         = 64;
     static private final int     TWENTYFOURBITGROUP   = 24;
@@ -288,4 +301,80 @@ public final class Base64
         }
         return newSize;
     }
+
+    /**
+     * 检查base64字符串是否是图片
+     *
+     * @param base64 base64字符串
+     * @return 是否为图片
+     */
+    public static boolean checkBase64IsImage(String base64) {
+        try {
+            // 将 data:image/jpg;base64, 去掉
+            int i = base64.indexOf(",");
+            base64 = base64.substring(i + 1);
+            // 图片内容 base64 解密。
+            byte[] data = Base64.decode(base64); // 校验是否是图片格式
+            InputStream inputStream = new ByteArrayInputStream(data);
+            BufferedImage image = ImageIO.read(inputStream);
+            // 如果成功创建BufferedImage，且其宽度和高度大于0，则认为是图片
+            return image != null && image.getWidth() > 0 && image.getHeight() > 0;
+        } catch (Exception e) {
+            logger.error("校验base64是否为图片失败：{}", e.getMessage());
+            return false;
+        }
+    }
+
+    /**
+     * 将网络图片转换为Base64字符串
+     *
+     * @param imageUrl 图片地址
+     * @return 图片base64字符串
+     */
+    public static String imageUrlToBase64(String imageUrl) {
+
+        try {
+            // 从URL获取图片输入流
+            URL url = new URL(imageUrl);
+            InputStream inputStream = url.openStream();
+
+            // 读取图片输入流并转换为字节数组
+            byte[] imageBytes = readAllBytes(inputStream);
+
+            // 获取图片MIME类型
+            String mimeType = getImageMimeType(imageUrl);
+            String base64 = java.util.Base64.getEncoder().encodeToString(imageBytes);
+            if (!checkBase64IsImage(base64)) {
+                throw new ServiceException("上传的文件非图片类型");
+            }
+            ;
+            // 添加MIME类型前缀
+            return "data:" + mimeType + ";base64," + base64;
+        } catch (Exception e) {
+            throw new ServiceException("图片地址错误");
+        }
+    }
+
+    private static byte[] readAllBytes(InputStream inputStream) throws IOException {
+        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+        byte[] buffer = new byte[8192];
+        int bytesRead;
+        while ((bytesRead = inputStream.read(buffer)) != -1) {
+            byteArrayOutputStream.write(buffer, 0, bytesRead);
+        }
+        return byteArrayOutputStream.toByteArray();
+    }
+
+    private static String getImageMimeType(String imageUrl) throws IOException {
+        // 根据URL获取图片MIME类型
+        URL url = new URL(imageUrl);
+        InputStream inputStream = url.openStream();
+        String mimeType = java.net.URLConnection.guessContentTypeFromStream(inputStream);
+        if (mimeType == null) {
+            return "image/jpeg";
+        } else {
+            return mimeType;
+        }
+    }
+
 }