球拍博士中的位图 [英] bitmap in dr racket

问题描述

如何在 dr 球拍中的帧 (gui) 上加载位图???请给出必要的代码和参考资料....

how to load a bitmap on a frame (gui) in dr racket??? please give the necessary code and references....

推荐答案

我承认，我很难在文档中找到正确的位置来指向您.这里有一些代码可以做到这一点，但我偷偷怀疑有一种更简单的方法来完成这项工作:

I admit, I'm having a hard time finding the right spot in the docs to point you to. Here's some code that does it, but I have a sneaking suspicion that there's a much easier way to get this done:

#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)

update:Matthew Flatt 建议:您可以使用带有位图的 `message%' 作为它的标签.这当然少了很多代码.这取决于你打算去哪里.

update: Matthew Flatt suggests: You could use `message%' with the bitmap as its label. This is certainly lots less code. It depends on where you're going with this.

#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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