fix: add Image struct definition in opencv.cpp

pkg/opencv/opencv.cpp

@@ -5,6 +5,14 @@
 #include <string>
 #include <cstring>
 
+// 图像结构体定义
+typedef struct {
+    unsigned char* data;
+    int width;
+    int height;
+    int channels;
+} Image;
+
 static std::string last_error;
 
 extern "C" {