fix erroneous conversion to monochrome bitmaps

Author: bdeket

plot-lib/plot/private/no-gui/plot2d.rkt

@@ -98,8 +98,7 @@
                      #:y-label [y-label (plot-y-label)]
                      #:legend-anchor [legend-anchor (plot-legend-anchor)])
   (define bm : (Instance (Class #:implements Bitmap% #:implements Plot-Metrics<%>))
-    (make-object (plot-metrics-mixin bitmap%)
-      (λ () pm) width height #t 1.0))
+    (make-object (plot-metrics-mixin bitmap%) (λ () pm) width height))
   (define dc : (Instance DC<%>) (make-object bitmap-dc% bm))
   (define pm : (Instance Plot-Metrics<%>)
     (plot/dc renderer-tree dc 0 0 width height

plot-lib/plot/private/no-gui/plot3d.rkt

@@ -129,8 +129,7 @@
                        #:z-label [z-label (plot-z-label)]
                        #:legend-anchor [legend-anchor (plot-legend-anchor)])
   (define bm : (Instance (Class #:implements Bitmap% #:implements Plot-Metrics<%>))
-    (make-object (plot-metrics-mixin (class bitmap% (super-new)))
-      (λ () pm) width height #t 1.0))
+    (make-object (plot-metrics-mixin (class bitmap% (super-new))) (λ () pm) width height))
   (define dc : (Instance DC<%>) (make-object bitmap-dc% bm))
   (define pm : (Instance Plot-Metrics<%>)
     (plot3d/dc renderer-tree dc 0 0 width height