Image 在画布上设置图像列表的动画
我尝试使用以下代码在画布上显示图像列表。但是,在运行整个“for”循环并在帧中显示最终效果之前,将显示一个空帧,并且不会显示任何图像Image 在画布上设置图像列表的动画,image,animation,racket,Image,Animation,Racket,我尝试使用以下代码在画布上显示图像列表。但是,在运行整个“for”循环并在帧中显示最终效果之前,将显示一个空帧,并且不会显示任何图像 #lang racket/gui (require 2htdp/image) (define frame (new frame% [label "Example"] [width 500] [height 500])) (send frame s
#lang racket/gui
(require 2htdp/image)
(define frame (new frame%
[label "Example"]
[width 500]
[height 500]))
(send frame show #t)
; (sleep 1) ; tried this to allow time for frame to show properly; does not help;
(new canvas% [parent frame]
[paint-callback
(lambda (canvas dc)
(for ((i imglist)) ; imglist is a list of images to be displayed @ 1/second.
(send dc clear)
(send dc draw-bitmap
(image->bitmap i)
20 20)
; (send dc flush) ; this statement also does not help;
(sleep 1) ; to show animation effect from list of images;
))])
图像->位图功能来自:;发件人:
问题在哪里?如何解决?绘制回调旨在快速更新画布,然后返回。 当它返回时,系统知道画布已更新 一种方法是:1)引入一个参数,用于保存当前显示的图像。2) 进行
绘制回调
绘制当前图像。3) 创建一个单独的线程,每秒更改当前图像
注意:下面我在image->bitmap
中为宽度和高度添加了+1。圆圈的边缘被切掉了
#lang racket/gui
(require 2htdp/image)
(define images (list (circle 30 "outline" "red")
(circle 20 "outline" "red")
(circle 10 "outline" "red")
(circle 5 "outline" "red")))
(define current-image (make-parameter (first images)))
(define (image->bitmap image)
(let* ([width (+ (image-width image) 1)]
[height (+ (image-height image) 1)]
[bm (make-bitmap width height)]
[dc (send bm make-dc)])
(send dc clear)
(send image draw dc 0 0 0 0 width height 0 0 #f)
bm))
(define frame (new frame%
[label "Example"]
[width 500]
[height 500]))
(define canvas (new canvas% [parent frame]
[paint-callback
(lambda (canvas dc)
(send dc clear)
(send dc draw-bitmap (image->bitmap (current-image)) 20 20))]))
(send frame show #t)
(thread (λ ()
(let loop ([is images])
(cond
[(null? is) (loop images)]
[else (current-image (first is))
(send canvas on-paint)
(sleep 1)
(loop (rest is))]))))
以下工作:
(define images (list (circle 30 "outline" "red")
(circle 20 "outline" "red")
(circle 10 "outline" "red")
(circle 5 "outline" "red")))
(define (image->bitmap image)
(let* ([width (image-width image)]
[height (image-height image)]
[bm (make-bitmap width height)]
[dc (send bm make-dc)])
(send dc clear)
(send image draw dc 0 0 0 0 width height 0 0 #f)
bm))
(define frame (new frame% [label "Frame"] [width 300] [height 300]))
(define canvas (new canvas% [parent frame]))
(define dc (send canvas get-dc))
(send frame show #t)
(sleep/yield 1)
(let loop ()
(for ((i images))
(send dc clear)
(send dc draw-bitmap
(image->bitmap i)
20 20)
(sleep 0.5))
(loop))
但是,显示动画的帧不会关闭,但必须从IDE停止。是的,它工作得很好。我发现我也可以使用“(send canvas get dc)”来获取dc对象,然后在其上以无休止的循环绘制位图,但是帧关闭按钮不起作用,必须从DrRacket IDE停止该过程。使用线程的解决方案没有这样的问题。
(define images (list (circle 30 "outline" "red")
(circle 20 "outline" "red")
(circle 10 "outline" "red")
(circle 5 "outline" "red")))
(define (image->bitmap image)
(let* ([width (image-width image)]
[height (image-height image)]
[bm (make-bitmap width height)]
[dc (send bm make-dc)])
(send dc clear)
(send image draw dc 0 0 0 0 width height 0 0 #f)
bm))
(define frame (new frame% [label "Frame"] [width 300] [height 300]))
(define canvas (new canvas% [parent frame]))
(define dc (send canvas get-dc))
(send frame show #t)
(sleep/yield 1)
(let loop ()
(for ((i images))
(send dc clear)
(send dc draw-bitmap
(image->bitmap i)
20 20)
(sleep 0.5))
(loop))