Index: apps/plugins/imageviewer/imageviewer.c
===================================================================
--- apps/plugins/imageviewer/imageviewer.c	(リビジョン 28863)
+++ apps/plugins/imageviewer/imageviewer.c	(作業コピー)
@@ -148,8 +148,9 @@
 
     for (i = 0; i < tree->filesindir && buf_size > sizeof(char**); i++)
     {
-        if (!(dircache[i].attr & ATTR_DIRECTORY)
-            && get_image_type(dircache[i].name) != IMAGE_UNKNOWN)
+        /* add all files (i.e. exclude all directory). will be filtered out
+           when loading. */
+        if (!(dircache[i].attr & ATTR_DIRECTORY))
         {
             file_pt[entries] = dircache[i].name;
             /* Set Selected File. */
Index: apps/plugins/imageviewer/image_decoder.c
===================================================================
--- apps/plugins/imageviewer/image_decoder.c	(リビジョン 28863)
+++ apps/plugins/imageviewer/image_decoder.c	(作業コピー)
@@ -32,6 +32,7 @@
 /* check file type by extention */
 enum image_type get_image_type(const char *name)
 {
+    enum image_type type = IMAGE_UNKNOWN;
     static const struct {
         char *ext;
         enum image_type type;
@@ -42,18 +43,56 @@
         { ".jpeg",  IMAGE_JPEG },
         { ".png",   IMAGE_PNG  },
     };
+    static const struct {
+        char *magic;    /* magic number */
+        int length;     /* length of the magic number */
+        enum image_type type;
+    } magic_list[] = {
+        { "\x42\x4d", 2, IMAGE_BMP  },
+        { "\xff\xd8\xff\xe0", 4, IMAGE_JPEG },
+        { "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a", 8, IMAGE_PNG },
+    };
 
     const char *ext = rb->strrchr(name, '.');
-    int i;
-    if (!ext)
-        return IMAGE_UNKNOWN;
-
-    for (i = 0; i < (int)ARRAYLEN(ext_list); i++)
+    int i, fd;
+    char buf[12];
+    /* check extention */
+    if (ext) {
+        for (i = 0; i < (int)ARRAYLEN(ext_list); i++)
+        {
+            if (!rb->strcasecmp(ext, ext_list[i].ext))
+            {
+                type = ext_list[i].type;
+                break;
+            }
+        }
+        ext++; /* skip dot */
+    }
+    else
     {
-        if (!rb->strcasecmp(ext, ext_list[i].ext))
-            return ext_list[i].type;
+        ext = "???";
     }
-    return IMAGE_UNKNOWN;
+
+    fd = rb->open(name, O_RDONLY);
+    if (fd >= 0) {
+        rb->memset(buf, 0, sizeof buf);
+        rb->read(fd, buf, sizeof buf);
+        rb->close(fd);
+        for (i = 0; i < (int)ARRAYLEN(magic_list); i++)
+        {
+            if (!rb->memcmp(buf, magic_list[i].magic, magic_list[i].length))
+            {
+                if (type != magic_list[i].type) {
+                    rb->splashf(HZ*1,
+                        "File extension is not correct: %s -> %s",
+                        ext, decoder_names[type]);
+                }
+                type = magic_list[i].type;
+                break;
+            }
+        }
+    }
+    return type;
 }
 
 static void *decoder_handle = NULL;
Index: apps/plugins/imageviewer/image_decoder.h
===================================================================
--- apps/plugins/imageviewer/image_decoder.h	(リビジョン 28863)
+++ apps/plugins/imageviewer/image_decoder.h	(作業コピー)
@@ -39,8 +39,11 @@
     size_t size;
 };
 
+/* check file type by magic number or file extension */
 enum image_type get_image_type(const char *name);
+/* load image decoder */
 const struct image_decoder *load_decoder(struct loader_info *loader_info);
+/* release the loaded decoder */
 void release_decoder(void);
 
 #endif /* _IMAGE_DECODER_H */