<div dir="ltr">Yes, I think this is the right approach, too. <div> </div><div>Robby</div></div><div class="gmail_extra"> <div class="gmail_quote">On Mon, Mar 24, 2014 at 3:40 PM, Matthew Flatt <<a href="mailto:mflatt@cs.utah.edu" target="_blank">mflatt@cs.utah.edu</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Probably something like this function belongs in `pict`: ;; smoothed : pict -> pict ;; Produces a pict like `p`, but that always draws in ;; 'smoothed mode (define (smoothed p) (define draw-p (make-pict-drawer p)) (define p2 <div class=""> (dc (lambda (dc x y) </div> (define s (send dc get-smoothing)) (send dc set-smoothing 'smoothed) (draw-p dc x y) (send dc set-smoothing s)) (pict-width p) (pict-height p))) (make-pict (pict-draw p2) (pict-width p) (pict-height p) (pict-ascent p) (pict-descent p) (list p) #f (pict-last p))) <div class="HOEnZb"><div class="h5"> At Mon, 24 Mar 2014 21:00:37 +0100, Jens Axel Søgaard wrote: > Hi all, > > DrRacket draws pict values in REPL. It seems DrRacket uses the > smoothing mode 'aligned. > > Is there a way to change this to 'smooth ? > > Below is a program that draws graphs of functions of a single variable > using Bezier curves. > It turns out that the Bezier curves doesn't fit together nicely when > the smoothing mode > 'aligned is used. On the bitmap version below this results in a > slightly jagged appearance. > If rendered to pdf, it becomes painfully obvious when you zoom. > > If on the other 'smooth is used everything fits nicely together. > > [Does 'aligned move all control points?] > > The program below draws the graph of x^2 in two ways: The first use DrRacket to > convert a pict to bitmap without touching the smoothing mode, the second > explicitly set smoothing to 'smooth. > > #lang racket > (require racket/draw pict) > > (define (f x) (* x x)) > (define (df/dx x) (* 2 x)) > > (struct pt (x y) #:transparent) ; point > (struct vec (x y) #:transparent) ; vector > (struct bez (p0 p1 p2 p3) #:transparent) ; Bezier curve > > (define (vec* k v) ; multiply vector v with constant k > (vec (* k (vec-x v)) (* k (vec-y v)))) > > (define (pt+ p v) ; add vector v to point p > (pt (+ (pt-x p) (vec-x v)) (+ (pt-y p) (vec-y v)))) > > > (define (draw-bezs dc bs) ; assumes the end and start points of each curve match > (define p (new dc-path%)) > (match-define (list b0 b. ...) bs) > (match-define (bez (pt x0 y0) (pt x1 y1) (pt x2 y2) (pt x3 y3)) b0) > (send p move-to x0 y0) > (send p curve-to x1 y1 x2 y2 x3 y3) > (for ([b b.]) > (match-define (bez (pt x0 y0) (pt x1 y1) (pt x2 y2) (pt x3 y3)) b) > (send p curve-to x1 y1 x2 y2 x3 y3)) > (send dc draw-path p)) > > (define (graph #:samples [n 200]) > (define-values (xmin xmax ymin ymax) (values -1 1 -1 1)) > (define ε 1.0e-10) > (define (φ x) (pt x (f x))) ; x -> (x,f(x)) > (define (τ x) (vec 1 (df/dx x))) ; vector along tangent > (define Δx (/ (- xmax xmin) n)) > (define x0 xmin) > (define (xi i) (+ x0 (* i Δx))) > (define bs (for/list ([i (in-range 0 (+ n 1))]) > (define x0 (xi i)) > (define x3 (xi (+ i 1))) > ; See page 7 of: > ; <a href="http://www.math.ubc.ca/~cass/graphics/manual/pdf/ch6.pdf" target="_blank">http://www.math.ubc.ca/~cass/graphics/manual/pdf/ch6.pdf</a> > (bez (φ x0) > (pt+ (φ x0) (vec* (/ Δx 3) (τ x0))) > (pt+ (φ x3) (vec* (/ Δx -3) (τ x3))) > (φ x3)))) > ; return pict that draws the Bezier curves > (dc (lambda (dc x y) > (define-values (old-x0 old-y0) (send dc get-origin)) > (define-values (old-scale-x old-scale-y) (send dc get-scale)) > (define old-pen (send dc get-pen)) > (send dc set-origin 200 200) > (send dc set-scale 200 -200) > (send dc set-pen "black" 0 'solid) > (draw-bezs dc bs) > (send dc set-pen old-pen) > (send dc set-scale old-scale-x old-scale-y) > (send dc set-origin old-x0 old-y0)) > 400 400)) > > (define bm (make-object bitmap% 400 400)) > (define bm-dc (new bitmap-dc% [bitmap bm])) > (send bm-dc set-smoothing 'smoothed) > > (define p (graph #:samples 100)) > (draw-pict p bm-dc 0 0) > > (list p bm) > > > -- > Jens Axel Søgaard > > ____________________ > Racket Users list: > <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> ____________________ Racket Users list: <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </div></div></blockquote></div> </div>