在Python中为多边形创建圆角边

Question

我遇到了一个有趣的问题（How to make a tkinter canvas rectangle with rounded corners?），与在Tkinter中创建圆形矩形有关，特别是Francisco Gomes的回答（稍加修改）：

def roundPolygon(x, y, sharpness):

    # The sharpness here is just how close the sub-points
    # are going to be to the vertex. The more the sharpness,
    # the more the sub-points will be closer to the vertex.
    # (This is not normalized)
    if sharpness < 2:
        sharpness = 2

    ratioMultiplier = sharpness - 1
    ratioDividend = sharpness

    # Array to store the points
    points = []

    # Iterate over the x points
    for i in range(len(x)):
        # Set vertex
        points.append(x[i])
        points.append(y[i])

        # If it's not the last point
        if i != (len(x) - 1):
            # Insert submultiples points. The more the sharpness, the more these points will be
            # closer to the vertex. 
            points.append((ratioMultiplier*x[i] + x[i + 1])/ratioDividend)
            points.append((ratioMultiplier*y[i] + y[i + 1])/ratioDividend)
            points.append((ratioMultiplier*x[i + 1] + x[i])/ratioDividend)
            points.append((ratioMultiplier*y[i + 1] + y[i])/ratioDividend)
        else:
            # Insert submultiples points.
            points.append((ratioMultiplier*x[i] + x[0])/ratioDividend)
            points.append((ratioMultiplier*y[i] + y[0])/ratioDividend)
            points.append((ratioMultiplier*x[0] + x[i])/ratioDividend)
            points.append((ratioMultiplier*y[0] + y[i])/ratioDividend)
            # Close the polygon
            points.append(x[0])
            points.append(y[0])

当我将这段代码改编成我的图形库时，它已经足够好了！但当我创建一个“拉伸正方形”（非正方形矩形）时，圆度也会拉伸：

那么，如何更改此代码以删除拉伸的圆度并保持其恒定半径

Answer 1

这里有一种方法，它使用内置的tcl tk原语canvas.create_line和canvas.create_arc来构建各种大小和比例的圆角矩形（圆弧）

角半径表示为矩形(0.0 > 0.5)最短边的比例，可以参数化

函数make_round_corners_rect返回一个元组，其中包含作为矩形实体片段的所有canvas item ids。所有片段都使用其同伴的id进行标记，因此仅使用一个片段id就可以访问整个对象

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#! python3

import math
import tkinter as tk
from tkinter import TclError


def make_round_corners_rect(canvas, x0, y0, x1, y1, ratio=0.2, npts=12):

    if x0 > x1:
        x0, x1 = x1, x0
    if y0 > y1:
        y0, y1 = y1, y0
        
    r = min(x1 - x0, y1 - y0) * ratio
    
    items = []

    topleft = x0, y0
    tld = x0, y0 + r
    tlr = x0 + r, y0
    item = canvas.create_arc(x0, y0, x0+2*r, y0+2*r, start=90, extent=90, fill='', outline='black', style=tk.ARC)
    items.append(item)
    
    top_right = x1, y0
    trl = x1 - r, y0
    trd = x1, y0 + r
    item = canvas.create_line(*tlr, *trl, fill='black')
    items.append(item)
    item = canvas.create_arc(x1-2*r, y0, x1, y0+2*r, start=0, extent=90, fill='', outline='black', style=tk.ARC)
    items.append(item)

    bot_right = x1, y1
    bru = x1, y1 - r
    brl = x1 - r, y1
    item = canvas.create_line(*trd, *bru, fill='black')
    items.append(item)
    item = canvas.create_arc(x1-2*r, y1-2*r, x1, y1, start=270, extent=90, fill='', outline='black', style=tk.ARC)
    items.append(item)

    bot_left = x0, y1
    blr = x0 + r, y1
    blu = x0, y1 - r
    item = canvas.create_line(*brl, *blr, fill='black')
    items.append(item)
    item = canvas.create_arc(x0, y1-2*r, x0+2*r, y1, start=180, extent=90, fill='', outline='black', style=tk.ARC)
    items.append(item)
    item = canvas.create_line(*blu, *tld, fill='black')
    items.append(item)
    
    items = tuple(items)
    print(items)
    
    for item_ in items:
        for _item in items:
            canvas.addtag_withtag(item_, _item)

    return items


if __name__ == '__main__':

    root = tk.Tk()
    canvas = tk.Canvas(root, width=500, height=500)
    canvas.pack(expand=True, fill=tk.BOTH)

    TL = 100, 100
    BR = 400, 200
    make_round_corners_rect(canvas, *TL, *BR)
    
    TL = 100, 300
    BR = 400, 400
    make_round_corners_rect(canvas, *TL, *BR, ratio = .3)

    TL = 300, 50
    BR = 350, 450
    that_rect = make_round_corners_rect(canvas, *TL, *BR, ratio=.4)
    for fragment in that_rect:
        canvas.itemconfig(fragment, width=4)
        try:
            canvas.itemconfig(fragment, outline='blue')
        except TclError:
            canvas.itemconfig(fragment, fill='blue')

    
    TL = 150, 50
    BR = 200, 450
    make_round_corners_rect(canvas, *TL, *BR, ratio=.07)
    
    TL = 30, 30
    BR = 470, 470
    that_rect = make_round_corners_rect(canvas, *TL, *BR, ratio=.3)
    for fragment in that_rect:
        canvas.itemconfig(fragment, dash=(3, 3))
   
    TL = 20, 20
    BR = 480, 480
    make_round_corners_rect(canvas, *TL, *BR, ratio=.1)
    

    root.mainloop()

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下一步（留给读者作为练习）是在类中封装圆形矩形

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编辑：如何填充圆角矩形：

这有点复杂，从长远来看，可能需要一种方法，其中所有点都明确定义，形状形成为多边形，而不是tkinter原语的聚合。在此编辑中，圆角矩形由两个重叠矩形和四个圆盘填充；它允许创建填充/未填充的形状，但在创建后不更改该属性-尽管这样做不需要太多的工作。（收集画布ID，并结合outline属性按需打开/关闭它们）；然而，如前所述，将所有这些行为封装在一个模仿tk.canvas.items行为的类中更有意义

def make_round_corners_rect(canvas, x0, y0, x1, y1, ratio=0.2, npts=12, filled=False, fillcolor=''):
    ...
    if filled:
        canvas.create_rectangle(x0+r, y0, x1-r, y1, fill=fillcolor, outline='')
        canvas.create_rectangle(x0, y0+r, x1, y1-r, fill=fillcolor, outline='')
        canvas.create_oval(x0, y0, x0+2*r, y0+2*r, fill=fillcolor, outline='')
        canvas.create_oval(x1-2*r, y0, x1, y0+2*r, fill=fillcolor, outline='')
        canvas.create_oval(x1-2*r, y1-2*r, x1, y1, fill=fillcolor, outline='')
        canvas.create_oval(x0, y1-2*r, x0+2*r, y1, fill=fillcolor, outline='')
    ...

if __name__ == '__main__':
    ...
    TL = 100, 300
    BR = 400, 400
    make_round_corners_rect(canvas, *TL, *BR, ratio=.3, filled=True, fillcolor='cyan')
    ...

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