请问tkinter canvas create_line()关于画虚线时dash参数的详解与原理

问题描述#

在使用 tkinter canvas 的 create_line () 画虚线时，对于 dash 参数不是很理解，不太清楚是什么样的机制。
百度包括书上提的都是说 dash 元组的第一个数字是实线，第二个数字是空白，如此循环直到所有元组数字用完又重新开始。例如 dash=(5,3) 是产生 5 像素实线，3 像素空白。
实践时，我一直在根据这些解释去想它是怎样去划线的，可是怎么想都没想通，可否根据后面的示例帮忙解答下？谢谢

示例代码#

from tkinter import *


def get_screen_size(root):
    """获取屏幕宽高"""
    screen_width = root.winfo_screenwidth()
    screen_height = root.winfo_screenheight()
    return screen_width, screen_height


def get_center_location(root, width, height):
    """获取屏幕居中位置"""
    screen_width, screen_height = get_screen_size(root)
    return (screen_width - width) / 2, (screen_height - height) / 2


width = 800
height = 600
bg_color = '#39889f'
min_width = 400
min_height = 200

# 新建窗口
root = Tk()
root.title('such_test')  # 窗口标题
x, y = get_center_location(root, width, height)
root.geometry('%dx%d+%d+%d' % (width, height, x, y))  # 窗口宽高、位置
root.configure(bg=bg_color)  # 窗口背景色
root.maxsize(*get_screen_size(root))  # 设置窗口拖拽时的最大大小
root.minsize(min_width, min_height)  # 设置窗口拖拽时的最小大小
# root.overrideredirect(True)  # 去掉边框
root.config(cursor='heart')

# 画布
canvas = Canvas(root, width=width, height=height)
canvas.create_rectangle(0, 0, width, height, outline=None, fill=bg_color)
canvas.create_rectangle(0, 0, width, height, outline=None, activefill='skyblue', activestipple="gray50")
canvas.pack()

# 虚线
canvas.create_line(60, 100, 60, 200, dash=(3, 1))
canvas.create_line(70, 100, 70, 200, dash=(5, 1))
canvas.create_line(80, 100, 80, 200, dash=(3, 1, 1))
canvas.create_line(90, 100, 90, 200, dash=(3, 1, 1, 1))
canvas.create_line(100, 100, 100, 200, dash=(5, 2, 2, 2))
canvas.create_line(110, 100, 110, 200, dash=(5, 2, 2, 2, 2, 2))

root.mainloop()

我运行的效果#

请问tkinter canvas create_line()关于画虚线时dash参数的详解与原理

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Jason990420

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最佳答案

The first possible syntax is a list of integers. Each element represents the number of pixels of a line segment. Only the odd segments are drawn using the “outline” color. The other segments are drawn transparent.

-dash .     → -dash {2 4}
-dash -     → -dash {6 4}
-dash -.    → -dash {6 4 2 4}
-dash -..   → -dash {6 4 2 4 2 4}
-dash {. }  → -dash {2 8}
-dash ,     → -dash {4 4}

On systems which support only a limited set of dash patterns, the dash pattern will be displayed as the closest dash pattern that is available. For example, on Windows only the first 4 of the above examples are available. The last 2 examples will be displayed identically to the first one.

The result is different for Windows and non-Windows.

For Windows, only top four dash patterns work fine

canvas.create_line(60, 100, 60, 200, dash=(2, 4))
canvas.create_line(70, 100, 70, 200, dash=(6, 4))
canvas.create_line(80, 100, 80, 200, dash=(6, 4, 2, 4))
canvas.create_line(90, 100, 90, 200, dash=(6, 4, 2, 4, 2, 4))
canvas.create_line(100, 100, 100, 200, dash=(2, 8))
canvas.create_line(110, 100, 110, 200, dash=(4, 4))

file

For Linux,

canvas.create_line(60, 100, 60, 200, dash=(3, 1))
canvas.create_line(70, 100, 70, 200, dash=(5, 1))
canvas.create_line(80, 100, 80, 200, dash=(3, 1, 1))    # => (3, 1, 1, 3, 1, 1)
canvas.create_line(90, 100, 90, 200, dash=(3, 1, 1, 1))
canvas.create_line(100, 100, 100, 200, dash=(5, 2, 2, 2))
canvas.create_line(110, 100, 110, 200, dash=(5, 2, 2, 2, 2, 2))

file

2年前评论

Sucherly （楼主）

Thanks very much for your answer。I ran these code on Windows before,and never thought that there may be some difference between Windows and Linux。now I understand through the second picture. Then could I ask why does it work differently on Windows?

Jason990420 （作者）

@sucherly functionality provided by OS, so OS-dependent.

Sucherly （楼主）

@Jason990420 Well，I got it.Thank you so much!

讨论数量: 4

Jason990420

1.9k 声望 / 個人 @ 個人

The first possible syntax is a list of integers. Each element represents the number of pixels of a line segment. Only the odd segments are drawn using the “outline” color. The other segments are drawn transparent.

-dash .     → -dash {2 4}
-dash -     → -dash {6 4}
-dash -.    → -dash {6 4 2 4}
-dash -..   → -dash {6 4 2 4 2 4}
-dash {. }  → -dash {2 8}
-dash ,     → -dash {4 4}

On systems which support only a limited set of dash patterns, the dash pattern will be displayed as the closest dash pattern that is available. For example, on Windows only the first 4 of the above examples are available. The last 2 examples will be displayed identically to the first one.

The result is different for Windows and non-Windows.

For Windows, only top four dash patterns work fine

canvas.create_line(60, 100, 60, 200, dash=(2, 4))
canvas.create_line(70, 100, 70, 200, dash=(6, 4))
canvas.create_line(80, 100, 80, 200, dash=(6, 4, 2, 4))
canvas.create_line(90, 100, 90, 200, dash=(6, 4, 2, 4, 2, 4))
canvas.create_line(100, 100, 100, 200, dash=(2, 8))
canvas.create_line(110, 100, 110, 200, dash=(4, 4))

file

For Linux,

canvas.create_line(60, 100, 60, 200, dash=(3, 1))
canvas.create_line(70, 100, 70, 200, dash=(5, 1))
canvas.create_line(80, 100, 80, 200, dash=(3, 1, 1))    # => (3, 1, 1, 3, 1, 1)
canvas.create_line(90, 100, 90, 200, dash=(3, 1, 1, 1))
canvas.create_line(100, 100, 100, 200, dash=(5, 2, 2, 2))
canvas.create_line(110, 100, 110, 200, dash=(5, 2, 2, 2, 2, 2))

file

2年前评论

Sucherly （楼主）

Thanks very much for your answer。I ran these code on Windows before,and never thought that there may be some difference between Windows and Linux。now I understand through the second picture. Then could I ask why does it work differently on Windows?

Jason990420 （作者）

@sucherly functionality provided by OS, so OS-dependent.

Sucherly （楼主）

@Jason990420 Well，I got it.Thank you so much!

讨论应以学习和精进为目的。请勿发布不友善或者负能量的内容，与人为善，比聪明更重要！

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请问tkinter canvas create_line()关于画虚线时dash参数的详解与原理

问题描述#

示例代码#

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问题描述#

示例代码#

我运行的效果#

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