Fix local file reference to water.png image.

collects/scribblings/draw/guide.scrbl

@@ -3,6 +3,7 @@
           "common.ss"
           scribble/eval
           scribble/racket
+          racket/runtime-path
           (for-syntax racket/base)
           (for-label racket/math))
 
@@ -255,7 +256,13 @@ brush can have a @deftech{stipple}, which is a bitmap that is used
 instead of a solid color when drawing. For example, if
 @filepath{water.png} has the image
 
-@centered{@image["water.png"]}
+@;{We can't just use the runtime path for "water.png" because we need to 
+make the eval below work. }
+@(define-runtime-path here ".")
+@(define-runtime-path water "water.png")
+@(draw-eval `(current-directory ,here))
+
+@centered{@image[water]}
 
 then it can be loaded with @racket[read-bitmap] and installed as the
 stipple for @racket[blue-brush]: