dr racket中的位图

如何在dr racket中的框架（gui）上加载位图？？？

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请提供必要的代码和参考资料……

我承认，我很难在文档中找到正确的位置来为您指明方向。这里有一些代码可以做到这一点，但我暗自怀疑有一种更简单的方法可以做到这一点：

#lang racket

(require racket/draw
         mred)

;; define a canvas that displays a bitmap when its on-paint
;; method is called
(define bitmap-canvas%
  (class canvas%
    (init-field [bitmap #f])
    (inherit get-dc)
    (define/override (on-paint)
      (send (get-dc) draw-bitmap bitmap 0 0))
    (super-new)))

;; load the bitmap
(define bitmap (read-bitmap "/tmp/red-arrow.bmp"))

;; create a new frame (top-level window)
(define f (new frame% [label "foo"] [width 100] [height 100]))

;; create a canvas
(define the-canvas (new bitmap-canvas% [parent f] [bitmap bitmap]))

;; show the canvas
(send f show #t)

更新：Matthew Flatt建议：可以使用带有位图的“message%”作为标签。这当然是更少的代码。这取决于你要带着这个去哪里

#lang racket/gui

(define bitmap (read-bitmap "/tmp/red-arrow.bmp"))

(define f (new frame% [label "Bitmap"]))
(new message% [parent f] [label bitmap])
(send f show #t)

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我承认，我很难在文件中找到合适的位置来给你指点。这里有一些代码可以做到这一点，但我暗自怀疑有一种更简单的方法可以做到这一点：

#lang racket

(require racket/draw
         mred)

;; define a canvas that displays a bitmap when its on-paint
;; method is called
(define bitmap-canvas%
  (class canvas%
    (init-field [bitmap #f])
    (inherit get-dc)
    (define/override (on-paint)
      (send (get-dc) draw-bitmap bitmap 0 0))
    (super-new)))

;; load the bitmap
(define bitmap (read-bitmap "/tmp/red-arrow.bmp"))

;; create a new frame (top-level window)
(define f (new frame% [label "foo"] [width 100] [height 100]))

;; create a canvas
(define the-canvas (new bitmap-canvas% [parent f] [bitmap bitmap]))

;; show the canvas
(send f show #t)

更新：Matthew Flatt建议：可以使用带有位图的“message%”作为标签。这当然是更少的代码。这取决于你要带着这个去哪里

#lang racket/gui

(define bitmap (read-bitmap "/tmp/red-arrow.bmp"))

(define f (new frame% [label "Bitmap"]))
(new message% [parent f] [label bitmap])
(send f show #t)