Yes, I think this is the right approach, too. Robby
On Mon, Mar 24, 2014 at 3:40 PM, Matthew Flatt <[email protected]> wrote: > 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 > (dc (lambda (dc x y) > (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))) > > 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: > > ; > http://www.math.ubc.ca/~cass/graphics/manual/pdf/ch6.pdf > > (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: > > http://lists.racket-lang.org/users > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users >
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