[PaddlePaddle Hackathon4 No.185] Add PaddleDetection Models Deployment Java Examples (#1782)

* add java examples

* fix detail

* fix pre-config

---------

Co-authored-by: DefTruth <31974251+DefTruth@users.noreply.github.com>

examples/application/java/yolov8/cpp/infer_demo.cc

@@ -0,0 +1,53 @@
+#include "infer_demo.h"
+
+#include "fastdeploy/vision.h"
+
+std::string ConvertTo(JNIEnv *env, jstring jstr) {
+  if (!jstr) {
+    return "";
+  }
+  const jclass jstring_clazz = env->GetObjectClass(jstr);
+  const jmethodID getBytesID =
+      env->GetMethodID(jstring_clazz, "getBytes", "(Ljava/lang/String;)[B");
+  const jbyteArray jstring_bytes = reinterpret_cast<jbyteArray>(
+      env->CallObjectMethod(jstr, getBytesID, env->NewStringUTF("UTF-8")));
+
+  size_t length = static_cast<size_t>(env->GetArrayLength(jstring_bytes));
+  jbyte *jstring_bytes_ptr = env->GetByteArrayElements(jstring_bytes, NULL);
+
+  std::string res =
+      std::string(reinterpret_cast<char *>(jstring_bytes_ptr), length);
+  env->ReleaseByteArrayElements(jstring_bytes, jstring_bytes_ptr, JNI_ABORT);
+
+  env->DeleteLocalRef(jstring_bytes);
+  env->DeleteLocalRef(jstring_clazz);
+  return res;
+}
+
+JNIEXPORT void JNICALL Java_InferDemo_infer(JNIEnv *env, jobject thiz,
+                                            jstring modelPath,
+                                            jstring imagePath) {
+  std::string model_path = ConvertTo(env, modelPath);
+
+  // Configuration information for model inference
+  fastdeploy::RuntimeOption option;
+  auto model = fastdeploy::vision::detection::YOLOv8(
+      model_path, "", option, fastdeploy::ModelFormat::ONNX);
+
+  assert(model.Initialized());  // Check whether the model is successfully
+                                // initialized
+
+  std::string image_path = ConvertTo(env, imagePath);
+  cv::Mat im = cv::imread(image_path);
+  fastdeploy::vision::DetectionResult result;
+
+  assert(model.Predict(im,
+                       &result));  // Check whether the prediction is successful
+
+  std::cout << result.Str() << std::endl;
+
+  cv::Mat vis_im = fastdeploy::vision::Visualize::VisDetection(im, result, 0.5);
+  // sava the visual results
+  cv::imwrite("vis_result.jpg", vis_im);
+  std::cout << "Visualized result save in vis_result.jpg" << std::endl;
+}