vwebp_sdl: simple viewer based on SDL

Uses WebPToSDL() generic function defined in vwebp_sdl.[ch].
This function is not included in the libextras library, because it
would bring in an SDL dependency. Probably too heavy for now.

WebPToSDL() is separate, because it will be called used by the javascript
version of libwebp (through emscripten build rules)

Change-Id: Ic85b36f8ce4784f46023656278f6480be6802834

extras/vwebp_sdl.c

@@ -0,0 +1,96 @@
+// Copyright 2017 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// Simple SDL-based WebP file viewer.
+// Does not support animation, just static images.
+//
+// Press 'q' to exit.
+//
+// Author: James Zern (jzern@google.com)
+
+#include <stdio.h>
+
+#ifdef HAVE_CONFIG_H
+#include "webp/config.h"
+#endif
+
+#if defined(WEBP_HAVE_SDL)
+
+#include "webp_to_sdl.h"
+#include "webp/decode.h"
+#include "../imageio/imageio_util.h"
+
+#if defined(WEBP_HAVE_JUST_SDL_H)
+#include <SDL.h>
+#else
+#include <SDL/SDL.h>
+#endif
+
+static void ProcessEvents(void) {
+  int done = 0;
+  SDL_Event event;
+  while (!done && SDL_WaitEvent(&event)) {
+    switch (event.type) {
+      case SDL_KEYUP:
+        switch (event.key.keysym.sym) {
+          case SDLK_q: done = 1; break;
+          default: break;
+        }
+        break;
+      default: break;
+    }
+  }
+}
+
+int main(int argc, char* argv[]) {
+  int c;
+  int ok = 0;
+  for (c = 1; c < argc; ++c) {
+    const char* file = NULL;
+    const uint8_t* webp = NULL;
+    size_t webp_size = 0;
+    if (!strcmp(argv[c], "-h")) {
+      printf("Usage: %s [-h] image.webp [more_files.webp...]\n", argv[0]);
+      return 0;
+    } else {
+      file = argv[c];
+    }
+    if (file == NULL) continue;
+    if (!ImgIoUtilReadFile(file, &webp, &webp_size)) {
+      fprintf(stderr, "Error opening file: %s\n", file);
+      goto Error;
+    }
+    if (webp_size != (size_t)(int)webp_size) {
+      fprintf(stderr, "File too large.\n");
+      goto Error;
+    }
+    ok = WebpToSDL((const char*)webp, (int)webp_size);
+    free((void*)webp);
+    if (!ok) {
+      fprintf(stderr, "Error decoding file %s\n", file);
+      goto Error;
+    }
+    ProcessEvents();
+  }
+  ok = 1;
+
+ Error:
+  SDL_Quit();
+  return ok ? 0 : 1;
+}
+
+#else  // !WEBP_HAVE_SDL
+
+int main(int argc, const char *argv[]) {
+  fprintf(stderr, "SDL support not enabled in %s.\n", argv[0]);
+  (void)argc;
+  return 0;
+}
+
+#endif