Merge pull request #2931 from ferdnyc:wechat-iconv-fix

Link wechat_qrcode with libiconv on MinGW

* wechat_qrcode: explicit iconv dependency

Iconv isn't automatic on all systems, non-POSIX have a separate
libiconv that needs to be found in CMake and linked.

* Don't disable iconv on MinGW

* wechat_qrcode: Disable iconv if not found

Author: ferdnyc

modules/wechat_qrcode/CMakeLists.txt

@@ -1,6 +1,16 @@
 set(the_description "WeChat QR code Detector")
 ocv_define_module(wechat_qrcode opencv_core opencv_imgproc opencv_dnn WRAP java objc python js)
 
+# iconv support isn't automatic on some systems
+if(CMAKE_VERSION VERSION_GREATER "3.11")
+  find_package(Iconv QUIET)
+  if(Iconv_FOUND)
+    ocv_target_link_libraries(${the_module} Iconv::Iconv)
+  else()
+    ocv_target_compile_definitions(${the_module} PRIVATE "NO_ICONV=1")
+  endif()
+endif()
+
 # need to change
 set(wechat_qrcode_commit_hash "a8b69ccc738421293254aec5ddb38bd523503252")
 set(hash_detect_caffemodel "238e2b2d6f3c18d6c3a30de0c31e23cf")

modules/wechat_qrcode/src/zxing/zxing.hpp

@@ -27,7 +27,7 @@
 #define USE_ONED_WRITER 1
 #endif
 
-#if defined(__ANDROID_API__) || defined(_MSC_VER) || defined(__MINGW32__) || defined(__MINGW64__)
+#if defined(__ANDROID_API__) || defined(_MSC_VER)
 
 #ifndef NO_ICONV
 #define NO_ICONV