Add a SDL_image test tool. use IMG_Load() and display

tools/sdl_image_test/.gitignore

@@ -0,0 +1,2 @@
+showimage
+showimage.o

tools/sdl_image_test/Makefile

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+CFLAGS = -Wall -O -g
+
+CFLAGS += $(shell sdl-config --cflags)
+
+LDLIBS = $(shell sdl-config --libs)
+LDLIBS += $(shell pkg-config SDL_image --libs-only-l)
+
+LDFLAGS = $(shell pkg-config SDL_image --libs-only-L)
+
+.PHONY:	all clean
+
+all:	showimage
+
+clean:
+	$(RM) showimage *.o
+
+showimage:	showimage.o
+

tools/sdl_image_test/showimage.c

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+/* vim:expandtab:ts=2 sw=2:
+*/
+/*  Grafx2 - The Ultimate 256-color bitmap paint program
+ *  Gif Analyzer tool
+
+    Copyright 2018 Thomas Bernard
+
+    Grafx2 is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    as published by the Free Software Foundation; version 2
+    of the License.
+
+    Grafx2 is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Grafx2; if not, see <http://www.gnu.org/licenses/>
+*/
+
+#include <stdio.h>
+#include <SDL.h>
+#include <SDL_image.h>
+
+SDL_Surface * screen = NULL;
+
+int Show_IMG(const char * filename)
+{
+  SDL_Surface * image;
+  SDL_Rect dest;
+
+  image = IMG_Load(filename);
+  if(image == NULL) {
+    fprintf(stderr, "Cannot load image \"%s\"\n", filename);
+    return -1;
+  }
+  if(screen == NULL) {
+    screen = SDL_SetVideoMode(image->w, image->h, image->format->BitsPerPixel, 0);
+  }
+  dest.x = 0;
+  dest.y = 0;
+  dest.w = image->w;
+  dest.h = image->h;
+  if(screen != NULL) {
+    SDL_BlitSurface(image, NULL, screen, &dest);
+    SDL_UpdateRects(screen, 1, &dest);
+  } else {
+    fprintf(stderr, "no SDL screen open\n");
+  }
+  SDL_FreeSurface(image);
+  return 0;
+}
+
+void Manage_Events(void)
+{
+  SDL_Event event;
+
+  for(;;) {
+    SDL_WaitEvent(&event);
+    switch(event.type) {
+    case SDL_QUIT:
+      return;
+    case SDL_KEYDOWN:
+      if(event.key.keysym.sym == SDLK_ESCAPE) return; /* ESC to quit */
+      break;
+    case SDL_MOUSEBUTTONDOWN:
+      return; /* clic to quit */
+    default:
+      break;
+    }
+  }
+}
+
+int main(int argc, char * * argv)
+{
+  const char * filename;
+  if(argc < 2) {
+    fprintf(stderr, "Usage:\t%s <image>\n", argv[0]);
+    return 1;
+  }
+  filename = argv[1];
+
+  if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER) < 0) {
+	  fprintf(stderr, "*** SDL Init Error ***\n");
+	  return 1;
+  }
+  atexit(SDL_Quit);
+
+  SDL_WM_SetCaption(filename, filename); /* window caption, icon caption */
+
+  if(Show_IMG(filename) < 0)
+    return 1;
+  Manage_Events();
+  return 0;
+}