SVGWrite中的弧形和饼图
有没有人能分享一个用svgwrite（Python库）画弧形切片（像奶酪切片或吃豆人那样）的例子？我试着画一个从(100,100)开始的西北象限，但得到的形状很奇怪：
w = dwg.path(d="M 100,50 A 50,50 0 0 1 50,100 l 0,50 z", fill="#ffff00", stroke='none')
我查看了用Inkscape生成的svg文件的实际输出，这里是它的xml等价物：
<path
d="M 100,50 A 50,50 0 0 1 50,100 l 0,50 z"
style="fill:#ffff00;fill-opacity:1;fill-rule:nonzero;stroke:none"
sodipodi:type="arc"
sodipodi:cx="100"
sodipodi:cy="100"
sodipodi:rx="50"
sodipodi:ry="50"
sodipodi:start="4.71"
sodipodi:end="3.14"
/>
但是我无法做到：a) 让svgwrite生成这个形状；b) 如果我把svgwrite生成的svg文件中的这段代码替换成上面的代码，它也没有效果，可能是因为sodipodi命令是Inkscape特有的。
有没有人有这个的工作示例？
3 个回答
1
这里有一个函数的另一种实现方式，它使用了和cv2.ellipse类似的参数。也许对某些人会有用 :)
import math
import svgwrite
def arc(svg, position, radius, rotation, start, end, color="white"):
x0, y0 = position[0] + radius, position[1]
x1, y1 = position[0] + radius, position[1]
rad_start = math.radians(start % 360)
rad_end = math.radians(end % 360)
x0 -= (1 - math.cos(rad_start)) * radius
y0 += math.sin(rad_start) * radius
x1 -= (1 - math.cos(rad_end)) * radius
y1 += math.sin(rad_end) * radius
args = {'x0': x0,
'y0': y0,
'x1': x1,
'y1': y1,
'xradius': radius,
'yradius': radius,
'ellipseRotation': 0,
'swap': 1 if end > start else 0,
'large': 1 if abs(start - end) > 180 else 0,
}
# 'a/A' params: (rx,ry x-axis-rotation large-arc-flag,sweep-flag x,y)+ (case dictates relative/absolute pos)
path = """M %(x0)f,%(y0)f
A %(xradius)f,%(yradius)f %(ellipseRotation)f %(large)d,%(swap)d %(x1)f,%(y1)f
""" % args
arc = svg.path(d=path, fill="none", stroke=color, stroke_width=3)
arc.rotate(rotation, position)
svg.add(arc)
# start/end points, just for reference
svg.add(svg.circle((x0, y0), r=2, stroke="green", fill="green"))
svg.add(svg.circle((x1, y1), r=2, stroke="red", fill="red"))
# test it
svg = svgwrite.Drawing(filename="test.svg", size=(300, 300))
p0 = (150, 150)
svg.add(svg.rect((100, 100), (100, 100), stroke="orange", stroke_width=1, fill="none"))
svg.add(svg.circle(p0, r=2, stroke="orange", fill="orange"))
arc(svg, p0, 50, 0, 0, 210, color="black")
svg.save()
这个函数应该能给你类似这样的效果：
4
谢谢你，Douglas！我把你关于画弧的回答做成了一个函数，希望能帮助到其他人：
def addArc(dwg, current_group, p0, p1, radius):
""" Adds an arc that bulges to the right as it moves from p0 to p1 """
args = {'x0':p0[0],
'y0':p0[1],
'xradius':radius,
'yradius':radius,
'ellipseRotation':0, #has no effect for circles
'x1':(p1[0]-p0[0]),
'y1':(p1[1]-p0[1])}
current_group.add(dwg.path(d="M %(x0)f,%(y0)f a %(xradius)f,%(yradius)f %(ellipseRotation)f 0,0 %(x1)f,%(y1)f"%args,
fill="none",
stroke='red', stroke_width=line_stroke_width
))
# usage example:
import svgwrite
dwg = svgwrite.Drawing(filename="test.svg", debug=True, size=(4000,1000))
current_group = dwg.add(dwg.g(id=name, stroke='red', stroke_width=3, fill='none', fill_opacity=0 ))
addArc(dwg, current_group, p0=[10,10], p1=[40,10], radius=80)
dwg.save()
显然，你可以在上面的画弧函数后面加上 dwg.line() 来画出饼图的切片或者其他东西。
4
好的，经过阅读更多的文档和查看示例下的链接后，我有了一些新的理解。
http://www.w3.org/TR/SVG11/paths.html#PathData
这是一个在svgwrite中工作的楔形示例。
w = dwg.path(d="M0,0 v-150 a150,150 0 0,0 -150,150 z",
fill="#00ff00",
stroke="none",
)
这段代码给我提供了一个西北象限。
我想把我的圆分成10度的切割，所以我写了这段代码：
start_x = 250
start_y = 300
radius = 100
for i in range(36):
degree0 = 0 + i*10
degree1 = 10 + i*10
radians0 = math.radians(degree0)
radians1 = math.radians(degree1)
dx0 = radius*(math.sin(radians0))
dy0 = radius*(math.cos(radians0))
dx1 = radius*(math.sin(radians1))
dy1 = radius*(math.cos(radians1))
m0 = dy0
n0 = -dx0
m1 = -dy0 + dy1
n1 = dx0 - dx1
w = dwg.path(d="M {0},{1} l {2},{3} a {4},{4} 0 0,0 {5},{6} z".format(start_x, start_y, m0, n0, radius, m1, n1),
fill="#00ff00",
stroke="none",
)
elem.append(w)
这段代码明确给出了所有这些切割，如果你想进行三角函数运算的话，也可以明确使用。这是围绕(250,300)这个点，半径为100的切割段。
0 : d=" M 250,300 l 100.0,-0.0 a 100,100 0 0,0 -1.5192246987791975,-17.364817766693033 z "
10 : d=" M 250,300 l 98.4807753012208,-17.364817766693033 a 100,100 0 0,0 -4.511513222629958,-16.837196565873835 z "
20 : d=" M 250,300 l 93.96926207859084,-34.20201433256687 a 100,100 0 0,0 -7.366721700146968,-15.797985667433124 z "
30 : d=" M 250,300 l 86.60254037844388,-49.99999999999999 a 100,100 0 0,0 -9.998096066546069,-14.278760968653934 z "
40 : d=" M 250,300 l 76.60444431189781,-64.27876096865393 a 100,100 0 0,0 -12.325683343243867,-12.325683343243881 z "
50 : d=" M 250,300 l 64.27876096865394,-76.60444431189781 a 100,100 0 0,0 -14.278760968653927,-9.998096066546054 z "
60 : d=" M 250,300 l 50.000000000000014,-86.60254037844386 a 100,100 0 0,0 -15.797985667433132,-7.366721700146968 z "
70 : d=" M 250,300 l 34.20201433256688,-93.96926207859083 a 100,100 0 0,0 -16.837196565873843,-4.511513222629972 z "
80 : d=" M 250,300 l 17.36481776669304,-98.4807753012208 a 100,100 0 0,0 -17.364817766693033,-1.5192246987791975 z "
90 : d=" M 250,300 l 6.123233995736766e-15,-100.0 a 100,100 0 0,0 -17.364817766693037,1.5192246987791975 z "
100 : d=" M 250,300 l -17.36481776669303,-98.4807753012208 a 100,100 0 0,0 -16.83719656587384,4.511513222629958 z "
110 : d=" M 250,300 l -34.20201433256687,-93.96926207859084 a 100,100 0 0,0 -15.79798566743311,7.366721700146968 z "
120 : d=" M 250,300 l -49.99999999999998,-86.60254037844388 a 100,100 0 0,0 -14.278760968653962,9.998096066546069 z "
130 : d=" M 250,300 l -64.27876096865394,-76.60444431189781 a 100,100 0 0,0 -12.325683343243853,12.325683343243867 z "
140 : d=" M 250,300 l -76.6044443118978,-64.27876096865394 a 100,100 0 0,0 -9.998096066546083,14.278760968653948 z "
150 : d=" M 250,300 l -86.60254037844388,-49.99999999999999 a 100,100 0 0,0 -7.366721700146954,15.797985667433103 z "
160 : d=" M 250,300 l -93.96926207859083,-34.20201433256689 a 100,100 0 0,0 -4.511513222629972,16.837196565873864 z "
170 : d=" M 250,300 l -98.4807753012208,-17.364817766693026 a 100,100 0 0,0 -1.5192246987791975,17.364817766693015 z "
180 : d=" M 250,300 l -100.0,-1.2246467991473532e-14 a 100,100 0 0,0 1.5192246987791975,17.364817766693058 z "
190 : d=" M 250,300 l -98.4807753012208,17.364817766693047 a 100,100 0 0,0 4.511513222629958,16.83719656587382 z "
200 : d=" M 250,300 l -93.96926207859084,34.20201433256687 a 100,100 0 0,0 7.366721700146982,15.797985667433146 z "
210 : d=" M 250,300 l -86.60254037844386,50.000000000000014 a 100,100 0 0,0 9.998096066546054,14.278760968653913 z "
220 : d=" M 250,300 l -76.60444431189781,64.27876096865393 a 100,100 0 0,0 12.325683343243867,12.325683343243867 z "
230 : d=" M 250,300 l -64.27876096865394,76.6044443118978 a 100,100 0 0,0 14.278760968653899,9.998096066546054 z "
240 : d=" M 250,300 l -50.00000000000004,86.60254037844385 a 100,100 0 0,0 15.797985667433188,7.3667217001469965 z "
250 : d=" M 250,300 l -34.202014332566854,93.96926207859084 a 100,100 0 0,0 16.83719656587382,4.511513222629958 z "
260 : d=" M 250,300 l -17.364817766693033,98.4807753012208 a 100,100 0 0,0 17.364817766693015,1.5192246987791975 z "
270 : d=" M 250,300 l -1.8369701987210297e-14,100.0 a 100,100 0 0,0 17.364817766693015,-1.5192246987791833 z "
280 : d=" M 250,300 l 17.364817766692997,98.48077530122082 a 100,100 0 0,0 16.8371965658739,-4.511513222629986 z "
290 : d=" M 250,300 l 34.2020143325669,93.96926207859083 a 100,100 0 0,0 15.797985667433117,-7.366721700146968 z "
300 : d=" M 250,300 l 50.000000000000014,86.60254037844386 a 100,100 0 0,0 14.278760968653913,-9.998096066546054 z "
310 : d=" M 250,300 l 64.27876096865393,76.60444431189781 a 100,100 0 0,0 12.325683343243853,-12.325683343243853 z "
320 : d=" M 250,300 l 76.60444431189778,64.27876096865396 a 100,100 0 0,0 9.998096066546054,-14.278760968653913 z "
330 : d=" M 250,300 l 86.60254037844383,50.00000000000004 a 100,100 0 0,0 7.366721700147011,-15.797985667433181 z "
340 : d=" M 250,300 l 93.96926207859084,34.20201433256686 a 100,100 0 0,0 4.511513222629958,-16.83719656587382 z "
350 : d=" M 250,300 l 98.4807753012208,17.36481776669304 a 100,100 0 0,0 1.5192246987791975,-17.364817766693015 z "