Add experimental support for desktop Java

Based on pull request #31 (thanks to Eric Christiansen)
Support for Java is turned off by default and can be enabled setting
BUILD_opencv_java to ON (e.g. cmake -DBUILD_opencv_java=ON ..)

modules/java/generator/gen_java.py

@@ -871,7 +871,7 @@ public class %(jc)s {
 
 #include "converters.h"
 
-#ifdef DEBUG
+#if defined DEBUG && defined ANDROID
 #include <android/log.h>
 #define MODULE_LOG_TAG "OpenCV.%(m)s"
 #define LOGD(...) ((void)__android_log_print(ANDROID_LOG_DEBUG, MODULE_LOG_TAG, __VA_ARGS__))

modules/java/generator/src/cpp/Mat.cpp

@@ -2,6 +2,8 @@
 
 #include "converters.h"
 
+#ifdef ANDROID
+
 #include <android/log.h>
 #define LOG_TAG "org.opencv.core.Mat"
 #define LOGE(...) ((void)__android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__))
@@ -11,6 +13,11 @@
 #define LOGD(...)
 #endif //DEBUG
 
+#else
+#define LOGE(...)
+#define LOGD(...)
+#endif
+
 #include "opencv2/core/core.hpp"
 
 using namespace cv;

modules/java/generator/src/cpp/utils.cpp

@@ -3,6 +3,8 @@
 #include "opencv2/core/core.hpp"
 #include "opencv2/imgproc/imgproc.hpp"
 
+#ifdef ANDROID
+
 #include <android/bitmap.h>
 
 #include <android/log.h>
@@ -165,3 +167,5 @@ JNIEXPORT void JNICALL Java_org_opencv_android_Utils_nMatToBitmap
 }
 
 } // extern "C"
+
+#endif //ANDROID