FS#11819: image viewer: use magick number in file to determine image type.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29110 a1c6a512-1295-4272-9138-f99709370657

apps/plugins/imageviewer/image_decoder.c

@@ -32,8 +32,14 @@ static const char *decoder_names[MAX_IMAGE_TYPES] = {
 #endif
 };
 
-/* check file type by extention */
-enum image_type get_image_type(const char *name)
+/* Check file type by magic number or file extension
+ *
+ * If the file contains magic number, use it to determine image type.
+ * Otherwise use file extension to determine image type.
+ * If the file contains magic number and file extension is not correct,
+ * informs user that something is wrong.
+ */
+enum image_type get_image_type(const char *name, bool quiet)
 {
     static const struct {
         char *ext;
@@ -48,18 +54,60 @@ enum image_type get_image_type(const char *name)
         { ".ppm",   IMAGE_PPM  },
 #endif
     };
+    static const struct {
+        char *magic;    /* magic number */
+        int length;     /* length of the magic number */
+        enum image_type type;
+    } magic_list[] = {
+        { "BM", 2, IMAGE_BMP },
+        { "\xff\xd8\xff\xe0", 4, IMAGE_JPEG },
+        { "\x89\x50\x4e\x47\x0d\x0a\x1a\x0a", 8, IMAGE_PNG },
+#ifdef HAVE_LCD_COLOR
+        { "P3", 2, IMAGE_PPM },
+        { "P6", 2, IMAGE_PPM },
+#endif
+    };
 
+    enum image_type type = IMAGE_UNKNOWN;
     const char *ext = rb->strrchr(name, '.');
-    int i;
-    if (!ext)
-        return IMAGE_UNKNOWN;
+    int i, fd;
+    char buf[12];
 
-    for (i = 0; i < (int)ARRAYLEN(ext_list); i++)
+    /* check file extention */
+    if (ext)
     {
-        if (!rb->strcasecmp(ext, ext_list[i].ext))
-            return ext_list[i].type;
+        for (i = 0; i < (int)ARRAYLEN(ext_list); i++)
+        {
+            if (!rb->strcasecmp(ext, ext_list[i].ext))
+            {
+                type = ext_list[i].type;
+                break;
+            }
+        }
     }
-    return IMAGE_UNKNOWN;
+
+    /* check magic value in the file */
+    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 (!quiet && type != magic_list[i].type)
+                {
+                    /* file extension is wrong. */
+                    rb->splashf(HZ*1, "Note: File extension is not correct");
+                }
+                type = magic_list[i].type;
+                break;
+            }
+        }
+    }
+    return type;
 }
 
 static void *decoder_handle = NULL;
@@ -79,7 +127,7 @@ const struct image_decoder *load_decoder(struct loader_info *loader_info)
     release_decoder();
 
     name = decoder_names[loader_info->type];
-    rb->snprintf(filename, MAX_PATH, VIEWERS_DIR "/%s.ovl", name);
+    rb->snprintf(filename, MAX_PATH, "/rockbox/rocks/viewers" "/%s.ovl", name);
 
     /* load decoder to the buffer. */
     decoder_handle = rb->lc_open(filename, loader_info->buffer, loader_info->size);

apps/plugins/imageviewer/image_decoder.h

@@ -42,8 +42,11 @@ struct loader_info {
     size_t size;
 };
 
-enum image_type get_image_type(const char *name);
+/* Check file type by magic number or file extension */
+enum image_type get_image_type(const char *name, bool quiet);
+/* 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 */

apps/plugins/imageviewer/imageviewer.c

@@ -148,8 +148,8 @@ static void get_pic_list(void)
 
     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. Non-image files will be filtered out while loading. */
+        if (!(dircache[i].attr & ATTR_DIRECTORY))
         {
             file_pt[entries] = dircache[i].name;
             /* Set Selected File. */
@@ -742,7 +742,13 @@ static int load_and_show(char* filename, struct image_info *info)
 
     rb->lcd_clear_display();
 
-    status = get_image_type(filename);
+    /* suppress warning while running slideshow */
+    status = get_image_type(filename, iv_api.running_slideshow);
+    if (status == IMAGE_UNKNOWN) {
+        /* file isn't supported image file, skip this. */
+        file_pt[curfile] = NULL;
+        return change_filename(direction);
+    }
     if (image_type != status) /* type of image is changed, load decoder. */
     {
         struct loader_info loader_info = {
@@ -914,7 +920,7 @@ enum plugin_status plugin_start(const void* parameter)
     if(!parameter) return PLUGIN_ERROR;
 
     rb->strcpy(np_file, parameter);
-    if (get_image_type(np_file) == IMAGE_UNKNOWN)
+    if (get_image_type(np_file, false) == IMAGE_UNKNOWN)
     {
         rb->splash(HZ*2, "Unsupported file");
         return PLUGIN_ERROR;