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

1 files changed, 58 insertions, 10 deletions

diff --git a/apps/plugins/imageviewer/image_decoder.c b/apps/plugins/imageviewer/image_decoder.c
index 553632e559..0088eb4873 100644
--- a/apps/plugins/imageviewer/image_decoder.c
+++ b/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];
+
+    /* check file 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;
+            }
+        }
+    }
 
-    for (i = 0; i < (int)ARRAYLEN(ext_list); i++)
+    /* check magic value in the file */
+    fd = rb->open(name, O_RDONLY);
+    if (fd >= 0)
     {
-        if (!rb->strcasecmp(ext, ext_list[i].ext))
-            return ext_list[i].type;
+        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 IMAGE_UNKNOWN;
+    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);