Respect jpeg format setting as scene snapshot and respect size setting when...

Respect jpeg format setting as scene snapshot and respect size setting when both width and height are set.

modules/video_filter/scene.c

@@ -275,7 +275,10 @@ static void SavePicture( filter_t *p_filter, picture_t *p_pic )
     fmt_out.i_sar_num = fmt_out.i_sar_den = 1;
     fmt_out.i_width = p_sys->i_width;
     fmt_out.i_height = p_sys->i_height;
+    if( !strncmp( p_sys->psz_format, "png", 3 ) )
         fmt_out.i_chroma = VLC_FOURCC('p','n','g',' ');
+    else
+        fmt_out.i_chroma = VLC_FOURCC('j','p','e','g');
 
     if( (fmt_out.i_width == 0) && (fmt_out.i_height > 0) )
     {
@@ -285,7 +288,7 @@ static void SavePicture( filter_t *p_filter, picture_t *p_pic )
     {
         fmt_out.i_height = (fmt_in.i_height * fmt_out.i_width) / fmt_in.i_width;
     }
-    else
+    else if( (fmt_out.i_width == 0) && (fmt_out.i_height == 0) )
     {
         fmt_out.i_width = fmt_in.i_width;
         fmt_out.i_height = fmt_in.i_height;