configure: mingw32 targets: test for WIC support

Replace usage of _WIN32 in examples as this does not guarantee the
presence of wincodec.h.
mingw-w64 notably includes wincodec.h, though other releases do not.

Under cygwin the following can be used for a WIC enabled binary:
./configure --target=i686-pc-mingw32 CC=i686-w64-mingw32-gcc.exe

Change-Id: Ica6a714c3356a8eaf88486a1c3f5aa6adde394c0

Makefile.vc

@@ -35,7 +35,8 @@ PLATFORM_LDFLAGS = /SAFESEH
 MT         = mt.exe
 CCNODBG    = cl.exe /nologo /O2 /DNDEBUG
 CCDEBUG    = cl.exe /nologo /Od /Gm /Zi /D_DEBUG /RTC1
-CFLAGS     = /Isrc /nologo /W3 /EHsc /DWIN32 /FD /c /GS /D_CRT_SECURE_NO_WARNINGS
+CFLAGS     = /Isrc /nologo /W3 /EHsc /FD /c /GS
+CFLAGS     = $(CFLAGS) /DWIN32 /D_CRT_SECURE_NO_WARNINGS /DHAVE_WINCODEC_H
 LDFLAGS    = /LARGEADDRESSAWARE /MANIFEST /NXCOMPAT /DYNAMICBASE $(PLATFORM_LDFLAGS)
 CFLAGSLIB  = /DLIBWEBP_STATICLIB
 LNKDLL     = link.exe /DLL

configure.ac

@@ -1,4 +1,5 @@
 AC_INIT([webpdecode], [0.1])
+AC_CANONICAL_TARGET
 AM_INIT_AUTOMAKE([-Wall foreign subdir-objects])
 AC_PROG_LIBTOOL
 AM_PROG_CC_C_O
@@ -74,6 +75,49 @@ AC_CHECK_HEADER(jpeglib.h,
 AC_SUBST(JPEG_LIBS)
 AC_SUBST(JPEG_INCLUDES)
 
+dnl === check for WIC support ===
+
+if test "$target_os" = "mingw32"; then
+  AC_CHECK_HEADERS([wincodec.h shlwapi.h windows.h])
+  if test "$ac_cv_header_wincodec_h" = "yes"; then
+    AC_MSG_CHECKING(for Windows Imaging Component support)
+    saved_LIBS=$LIBS
+    LIBS="-lshlwapi -lole32 $LIBS"
+    # match include structure from [cd]webp.c
+    wic_headers="
+      #define INITGUID
+      #define CINTERFACE
+      #define COBJMACROS
+      #define _WIN32_IE 0x500
+
+      #include <shlwapi.h>
+      #include <windows.h>
+      #include <wincodec.h>
+      "
+    # test for functions from each lib and the GUID is created properly
+    wic_main="
+      int main(void) {
+        CLSID_WICImagingFactory;
+        CoInitialize(NULL);
+        SHCreateStreamOnFile(NULL, 0, NULL);
+        return 0;
+      }
+      "
+    AC_LANG_PUSH(C)
+    AC_LINK_IFELSE(
+      [AC_LANG_SOURCE([
+         $wic_headers
+         $wic_main])],
+      [wic_support=yes],
+      [wic_support=no]
+    )
+    AC_LANG_POP
+
+    test "$wic_support" = "yes" || LIBS=$saved_LIBS
+    AC_MSG_RESULT(${wic_support-no})
+  fi
+fi
+
 dnl === If --enable-experimental is defined, add the flag WEBP_EXPERIMENTAL_FEATURES
 
 USE_EXPERIMENTAL_CODE=""

examples/cwebp.c

@@ -14,6 +14,10 @@
 #include <stdlib.h>
 #include <string.h>
 
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
 #ifdef WEBP_HAVE_PNG
 #include <png.h>
 #endif
@@ -23,7 +27,10 @@
 #include <jpeglib.h>
 #endif
 
-#ifdef _WIN32
+#ifdef HAVE_WINCODEC_H
+#ifdef __MINGW32__
+#define INITGUID  // Without this GUIDs are declared extern and fail to link
+#endif
 #define CINTERFACE
 #define COBJMACROS
 #define _WIN32_IE 0x500  // Workaround bug in shlwapi.h when compiling C++
@@ -31,7 +38,13 @@
 #include <shlwapi.h>
 #include <windows.h>
 #include <wincodec.h>
+
+#ifndef GUID_WICPixelFormat24bppRGB
+// From Microsoft SDK 7.0a
+DEFINE_GUID(GUID_WICPixelFormat24bppRGB,
+    0x6fddc324, 0x4e03, 0x4bfe, 0xb1, 0x85, 0x3d, 0x77, 0x76, 0x8d, 0xc9, 0x0d);
 #endif
+#endif  /* HAVE_WINCODEC_H */
 
 
 #include "webp/encode.h"
@@ -69,7 +82,7 @@ static int ReadYUV(FILE* in_file, WebPPicture* const pic) {
   return ok;
 }
 
-#ifdef _WIN32
+#ifdef HAVE_WINCODEC_H
 
 #define IFS(fn)                \
   do {                         \
@@ -183,7 +196,7 @@ static int ReadPicture(const char* const filename, WebPPicture* const pic,
   return ok;
 }
 
-#else  // !_WIN32
+#else  // !HAVE_WINCODEC_H
 
 #ifdef WEBP_HAVE_JPEG
 struct my_error_mgr {
@@ -425,7 +438,7 @@ static int ReadPicture(const char* const filename, WebPPicture* const pic,
   return ok;
 }
 
-#endif  // !_WIN32
+#endif  // !HAVE_WINCODEC_H
 
 static void AllocExtraInfo(WebPPicture* const pic) {
   const int mb_w = (pic->width + 15) / 16;
@@ -589,7 +602,7 @@ static void HelpLong(void) {
   printf(" cwebp [-preset <...>] [options] in_file [-o out_file]\n\n");
   printf("If input size (-s) for an image is not specified, "
          "it is assumed to be a PNG or JPEG file.\n");
-#ifdef _WIN32
+#ifdef HAVE_WINCODEC_H
   printf("Windows builds can take as input any of the files handled by WIC\n");
 #endif
   printf("options:\n");

examples/dwebp.c

@@ -17,11 +17,18 @@
 #include <stdlib.h>
 #include <string.h>
 
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
 #ifdef WEBP_HAVE_PNG
 #include <png.h>
 #endif
 
-#ifdef _WIN32
+#ifdef HAVE_WINCODEC_H
+#ifdef __MINGW32__
+#define INITGUID  // Without this GUIDs are declared extern and fail to link
+#endif
 #define CINTERFACE
 #define COBJMACROS
 #define _WIN32_IE 0x500  // Workaround bug in shlwapi.h when compiling C++
@@ -42,7 +49,7 @@ extern "C" {
 
 static int verbose = 0;
 
-#ifdef _WIN32
+#ifdef HAVE_WINCODEC_H
 
 #define IFS(fn)                \
   do {                         \
@@ -116,7 +123,7 @@ static int WritePNG(const char* out_file_name, unsigned char* rgb, int stride,
              height));
 }
 
-#elif defined(WEBP_HAVE_PNG)    // !WIN32
+#elif defined(WEBP_HAVE_PNG)    // !HAVE_WINCODEC_H
 static void PNGAPI error_function(png_structp png, png_const_charp dummy) {
   (void)dummy;  // remove variable-unused warning
   longjmp(png_jmpbuf(png), 1);
@@ -156,7 +163,7 @@ static int WritePNG(FILE* out_file, unsigned char* rgb, int stride,
   png_destroy_write_struct(&png, &info);
   return 1;
 }
-#else    // !WIN32 && !WEBP_HAVE_PNG
+#else    // !HAVE_WINCODEC_H && !WEBP_HAVE_PNG
 
 typedef uint32_t png_uint_32;
 
@@ -359,7 +366,7 @@ int main(int argc, const char *argv[]) {
     if (!needs_open_file || fout) {
       int ok = 1;
       if (format == PNG) {
-#ifdef _WIN32
+#ifdef HAVE_WINCODEC_H
         ok &= WritePNG(out_file, out, stride, width, height, has_alpha);
 #else
         ok &= WritePNG(fout, out, stride, width, height, has_alpha);