python - 锯齿 tkinter 主循环帧持续时间？

Question

尝试使用 tkinter 为一系列 PIL 图像制作动画。我的帧持续时间 (ms) 的图表如下所示:

有人知道是什么导致了这种尖尖的锯齿图案吗？

这是一个重现的脚本:

from PIL import Image, ImageTk
import Tkinter

import time
import sys

def generate_frames(n):
    """
    keep n under 101 * 101
    """
    out = []
    last_pil = None
    for i in range(n):
        if last_pil:
            pil_image = last_pil.copy()
        else:
            pil_image = Image.new('L', (101, 101), 255)   
        x = i / 101
        y = i % 101
        pil_image.load()[x, y] = 0
        out.append(ImageTk.PhotoImage(pil_image))
        last_pil = pil_image

    return out

def draw():
    FRAME_COUNT =5000

    master = Tkinter.Tk()

    w = Tkinter.Canvas(master, width=302, height=302)
    w.create_rectangle(49, 49, 252, 252)
    w.pack()

    frames = generate_frames(FRAME_COUNT)

    def draw_frame(f, canvas_image):
        print repr(time.time())
        frame = frames[f]
        if canvas_image is None:
            canvas_image = w.create_image((151, 151), image=frame, anchor='center')
        else:
            w.itemconfigure(canvas_image, image=frame)

        w.current_frame = frame  # save a reference
        next_frame = f + 1
        if next_frame < FRAME_COUNT:
            master.after(1, draw_frame, next_frame, canvas_image)
        else:
            sys.exit(0)

    master.after(10, draw_frame, 0, None)
    master.mainloop()


draw()

要查看绘图，请通过管道输出

import sys

last = None
for line in sys.stdin:
    value = float(line.strip()) * 1000
    if last is None:
        pass
    else:
        print (value - last)
    last = value

然后通过

from matplotlib import pyplot
import sys

X = []
Y = []

for index, line in enumerate(sys.stdin):
    line = line.strip()
    X.append(index)
    Y.append(float(line))

pyplot.plot(X, Y, '-')
pyplot.show()

使其成为多线程没有帮助:

class AnimationThread(threading.Thread):

    FRAME_COUNT = 5000

    def __init__(self, canvas):
        threading.Thread.__init__(self)
        self.canvas = canvas
        self.frames = generate_frames(self.FRAME_COUNT)

    def run(self):
        w = self.canvas
        frames = self.frames
        canvas_image = None
        for i in range(self.FRAME_COUNT):
            print repr(time.time())
            frame = frames[i]
            if canvas_image is None:
                canvas_image = w.create_image((151, 151), image=frame, anchor='center')
            else:
                w.itemconfigure(canvas_image, image=frame)
            w.current_frame = frame
            time.sleep(1 * .001)

def draw_threaded():
    FRAME_COUNT = 5000
    master = Tkinter.Tk()

    w = Tkinter.Canvas(master, width=302, height=302)
    w.create_rectangle(49, 49, 252, 252)
    w.pack()

    animation_thread = AnimationThread(w)
    animation_thread.start()

    master.mainloop()

    animation_thread.join()

draw_threaded()

Answer 1

当 60 赫兹和 50 赫兹的竞争样本混合时，这与这种干涉图非常相似:

(Original Wolfram|Alpha plot)

这可能是由于两个事物的刷新率不同(但接近)所致。这与当您尝试拍摄电视屏幕时发生的相同类型的事情，它看起来像一个黑条一直向下移动图像，或者当汽车车轮似乎围绕其轴向后旋转时在汽车广告中发生。它本质上是 Moiré Effect 的扩展.

我不知道它是否是由视频驱动程序和/或硬件引起的，但几乎可以肯定是由干扰循环模式引起的。看起来应该是 GC 循环干扰了您的 for 循环(因此随着内存被释放并可以分配，锯齿波突然下降)