Output of drawings to files

Questions & Answers
1

Is it possible to output a drawing made with the draw module or Metapict or the turtle graphics library to a file such as png or jpeg?

2

The save-pict function from metapict can be used to save picts as png files (or jpeg for that matter).

3

Do you mean something like that:

#lang racket

(require pict)
(require racket/draw)
(require pict-abbrevs)

(define points '((100 . 100) (0 . 0)))

(define (connect-points dc dx dy join)
  (define a-pen
    (send the-pen-list find-or-create-pen "black" 10 'solid 'round join))
  (send dc set-pen a-pen)
  (send dc draw-lines points dx dy))

(define a-dc
  (dc
   (λ (dc dx dy)
     (define old-pen (send dc get-pen))
     (connect-points dc 20 50 'round)
     (send dc set-pen old-pen))
   460 170))

(save-pict "foo.png" a-dc 'png)
4

No. If I learn how to use turtle graphics in Racket, will I find that I can save the output from it to a file, either as a raster image or vector graphics?

5

There are several turtle libraries.

This example implements the turtle commands, then draws the Peano curve.

If you use

then use save-turtle-bitmap .

If you use

then you get a pict, which you can then save in different formats.

6

Essentially all drawing libraries in Racket are higher-level layers over racket/draw, which can save a drawing context as SVG, PDF, PostScript, PNG, JPG, and a few miscellaneous raster formats.

Some higher-level libraries for things like turtle graphics may make these things more convenient than others, but the underlying functionality is definitely always there.

7

The turtle example they showed is more about implementing the turtle interface itself — you'd still need to hook it into something that can actually write to a file. Looking at that peano.rkt example, the turtle state is building up a list of line segments, but there's no saving step. You'd want to either render those lines to a pict (which you can then save with save-pict) or draw them to a dc like in the second reply. The dc approach is probably more direct if you're going the turtle route.

8

The last expression turns the curves into a pict.
If run in DrRacket the image will be displayed in the repl.

;;; Produce image
(set-curve-pict-size 400 400)
(with-window (window -1 81 -1 82)
  (peano 6 90 3)
  (draw* c))