Bug fix own collection:

- Recreate mipmaps if they're dirty when drawing background image
   (this prevents "delayed" update of background image when you're paiting on it
    in image editor).
 - Mark mipmaps as dirty when inverting image channels.

TODO: there's memory leak caused by IMB_remakemipmap, but it'll be
      anuther bugfix commit after discussion with other devs.

source/blender/editors/space_image/image_ops.c

@@ -1423,6 +1423,9 @@ static int image_invert_exec(bContext *C, wmOperator *op)
 	}
 
 	ibuf->userflags |= IB_BITMAPDIRTY;
+	if(ibuf->mipmap[0])
+		ibuf->userflags |= IB_MIPMAP_INVALID;
+
 	WM_event_add_notifier(C, NC_IMAGE|NA_EDITED, ima);
 	return OPERATOR_FINISHED;
 }

source/blender/editors/space_view3d/view3d_draw.c

@@ -1317,7 +1317,11 @@ static void draw_bgpic(Scene *scene, ARegion *ar, View3D *v3d)
 				float tzoom= MIN2(zoomx, zoomy);
 				int mip= 0;
 
-				if(ibuf->mipmap[0]==NULL)
+				if((ibuf->userflags&IB_MIPMAP_INVALID) != 0) {
+					IMB_remakemipmap(ibuf, 0);
+					ibuf->userflags&= ~IB_MIPMAP_INVALID;
+				}
+				else if(ibuf->mipmap[0]==NULL)
 					IMB_makemipmap(ibuf, 0);
 
 				while(tzoom < 1.0f && mip<8 && ibuf->mipmap[mip]) {