probe with some success image files not containing number pattern but having recognized image extension

Originally committed as revision 7219 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/img2.c

@@ -154,10 +154,13 @@ static int find_image_range(int *pfirst_index, int *plast_index,
 
 static int image_probe(AVProbeData *p)
 {
-    if (av_filename_number_test(p->filename) && av_str2id(img_tags, p->filename))
-        return AVPROBE_SCORE_MAX;
-    else
-        return 0;
+    if (av_str2id(img_tags, p->filename)) {
+        if (av_filename_number_test(p->filename))
+            return AVPROBE_SCORE_MAX;
+        else
+            return AVPROBE_SCORE_MAX/2;
+    }
+    return 0;
 }
 
 enum CodecID av_guess_image2_codec(const char *filename){